EFFECT OF COAL-SMOKE POLLUTION ON GROWTH AND MORPHOLOGY OF VEGETATIVE PARTS
OF CERTAIN DICOTYLEDONS
DISSERTATION FOR MASTER OF PHILOSOPHY
IN
BOTANY
BY
SAMIA KHAN
DEPARTMENT OF BOTANY ALIGARH MUSLIM UNIVERSITY
ALIGARH (INDIA)
1991
fad In GomDutetf
1)S1786
5 AU5 1332
» — J t — I
ALIGARH MUSLIM UNIVERSITY DEPARTMENT OF BOTANY, ALI6ARH-202 002, INDIA Tel. (0571) 5676
A. K. M. GHOUSE M. Sc. Ph. D., F.L.S.. F.A.E.B. Prof«*sor
CERTIFICATE
It is to certify that the dissertation entitled "Effect of coal-smoke
pollution on growth and Biorphology of vegetative parts of certain
dicotyledons" is genuine work of Ms. Samia khan, rhis may be submitted
to the Aligarh Muslim university in candidacy for the award of M.Phil,
degree in Botany.
U.K.M. GHOUSK;
ACKNOWLEDGEMENTS
I bow in reverence to Allah Whose benign benidiction gave
me the required zeal for the completion of this work. Were it not for
His help and cause, this humble contribution would nave never become
a reality.
Many persons provide a helping hand in the preparation of
this dissertation. Krincipaj. research and library facilities were
provided by Professor A.K.M. Ghouse, Chairman Department of botany,
Aligarh Muslim University, Aligarh.
I deem pleasure in expressing my debt of gratitude to my
Supervisor, ur. Muhammad iqbal who baptised me into this fascinating
and thrilling field of the ijnvironmental Pollution Kesearch, His
unfailing guidance, co-operation and encouragement made this disser
tation a source of satisfaction and pleasure,
I offer my sincere thanks to Professijr Ziauddin Ahmad,
Dr. M.I.H. Khan and Dr. P.R. Khan for their co-operation and valuable
suggestions that 1 received every now and then,
For his customary zeal and willingne'ss in assisting and
anythingelse that needed to be done, without which none of the dead
lines along tlie way would have been met, sincere appreciation goes to
Mr. Mahmoodu5',zafar, Kesearch Scholar in tsotany,
I owe a debt to my laboratory collegues, Ms. Azra Parveen,
Mr. i'arooq A., Loan and Mr. Must if a K. Ansari, l.'or their cooperative
attitude and friendly counsel.
I shall be failing in my duty if I do not give well deserved
credit to my parents! for their blessing; and he],p. I'hey have been a
continuous moving source of inspiration in all )ny past and present
ventures.
(SAMIA KHAN)
CONTENTS
INTRODUCTION 1 -20
SOURCES OF AE^ POLLUTION E l - 2 5
hIR POLLUTION 26-31
AIR POLLUTION IMPACTS UM PLANTS o 32-50
C a r b o n d i o x i d e 51 - 5 8
S u l p h u r d i o x i d e 59-80
Oxides of n i t r o g e n INO^) «1-91
Ozone 92-106
F l o u r i d e 107-115
Acid r a i n 116-125
P a r t i c u l a t e p o l l u t a n t s 126-132
PLAN OF WORK 153-137
METHODOLOGY 138-145
STATISTICAL ANALYSIS 146-154
REFERENCES 155-216
INTRODUCTION
While; entering the last decades of the 20th century thai has
witnessed an unparalleled destruction on the one hand and unimagi
nable progiress on the other, we find ourselves at a crucial
crossroad In the long and tortuous history of the human race on
the Earth. One of the greatest evils of the modern civilization
is its pro:Fligate use of natural resources without any concein for
the enviorment. The growing human population and its increasing
demand for food and materials have taken a heavy toll of the Earth's
natural resources. Consequently, every parameter of our biosphere
i.e. the air we breath, the food we eat, the water we drink, the
drugs we use, the place we live in and the land (soil) we cultivate
upon, is becoming polluted by leaps and bounds.
The pollution caused by the large scale urbanization, indus
trialization and the excessive use of chemicals, fertilizers and
pesticides has lead to steady degradation of our soil, water and
air. As a result, the very survival of human race is at stake.
The enviromental pollution has assumed an alarming magnitude and
its frontiers have encompassed the entire globe. The global forum
on Enviroment and Development for Survival, in a gathering in
Oxford in April 1988, resolved to strengthen the global conscious
ness against the pollution, the most devastating challange being
faced by all and sundry.
: 2 :
Steve Van Matre (1984) of the George William College at
Chicago, estimated that in the present world only 20? of air is
breathable, only 1()5 of land is capable of being cultivated for
food production and just 1? of the Earth's water is portable.
The amount of pollutants such as hydrocarbons, nitrogen oxides,
carbon monoxide, sulphur dioxide and dust entering the air of
Calcutta and Howrah cities was estimated to be 1299 tons per day
(Sharma 1981). With the tremendous rise in the rate of pollution
the occurrence of blood cancer has grown five-fold than in the
last decades in Lucknow (Agarwal e;t al. 1982).
Modernisation of technology has committed a number of
violations of environmental safety and now almost every facet
of life poses a health rist. The products which are boon to
humanity on one hand are annihilator of the enviroment on the
other, as they are recklessely thrown off as waste in the water,
soil and air and invariably pollute the whole atmosphere. While
citing a commission Mr. Arif Mohammad Khan, the former Minister
of Energy, stated that the developing countries accounted for only
1.3 billion tonnes of carbon dioxide emmission out of a world wide
total of 6.2 billion tonnes, and that this will grow to 2.7
billion tonnes of total 10 million tonnes in the year 2010. India
has achieved its industrial revolution and green revolution almost
simultaneously. Therefore the industrial and agricultural waat -'
has made a greater impact on the Indian environment; the Ganga is
: 3 :
chocked by agricultural and industrial wastes in 27 urban
centres.
Delhi administration have made 'Pollution Squad' and
'Monitoring Centres' with a view to preventing high level of
air pollution due to motor vehicles. A sum of Rs. 35 lakh has
been proposed in the Eight Five year plan to protect environment
for Bihar'ji tribal sub-plan area. An agreement was reached at
the 1989 U«N. General Assembly Session to draft a treaty on sta
bilising the earth climate and convene a World Conference in
Brazil in 1992.
Pollution means direct or indirect changes in one or more
components of the ecosystem, making it least desirable for human
consumption. Weber (1982) defined pollution as 'the presence of
substances in the ambient atmosphere resulting from the activity
of man or from natural processes, causing adverse effects to man
and environment'. The environmental pollution includes several
pollutions such as soil pollution, water pollution, noise pollu
tion and air pollution. With the commencement of the 20th
century, the range of the atmospheric pollutants has widened
drastically. The tremendous use of petroleum products has caused
several new pollutants (WHO, 1972).
Billions of years ago, the atmosphere of the earth presuma
bly constituted ammonia, water vapours and methane. Our present
: 4 :
day oxygen-rich atmosphere is the consequence of an oxygen revo
lution brought about by the evolution of photosynthetic mechanism.
The atmospheric composition, on the geological time scale, has
undergone tremendous changes in the recent years, we have hastened
the pace of these changes by burning of fossil fuels and adding
numerous chemicals to the atmosphere.
The gaseous mass of pure air constituting the atmosphere is
15 estimated to be 5.15x10 tonnes (Sytnick 1985). The dry air
comprises the following :
Nitrogen 78.084%
Oxygen 20.9467%
Argon 0.934%
Carbon dioxide 0.0314%
Neon 0.0018%
Helium 0.0005%
Methane 0.0002%
Krypton 0.0001%
and hydrogen, xenon, ozone, ammonia, carbon monoxide and iodine
in still smaller traces (Sytnick 1985). In addition, it contains
dust, pollen grains and microganisms such as viruses, bacteria
and fungal spores. It also contains malodorous emmisions from
industries, forest fires, burning of fossil fuels that release
smoke, ash and odour.
: 5 :
The atmosphere is responsible for maintaining a difference
between day and night temperatures, and providing a shield around
the earth against lethal radiations and meteorites. Thus, the
atmosphere Is essential for life. 'Whenever emmisions from
industries, automobiles and decomposing waste get mixed up in the
air, there is an adverse effect on the life of plants, animals
and human health and/or damaging buildings by their exessive con
centrations, lethal or toxic nature or otherwise, we regard it
as air pollution'. Study of air pollution, indeed has expanded
multidirectionally as it is related to various diverse fields of
study such as ecology, meteorology, chemical engineering economics,
geography, geology, aviation and medical biology.
The antiquity of environmental pollution dates back to the
ancient Aryans, who performed 'Homa' ritual in order to purify
the air. The dangers of air pollution were first recognized in
the reign of Edward I (1272-1307) who prohibited the use of sea-
coal in open furnace (Martin, 1975). Edward II (1307-1327)
punished people for filling air with a 'pestilential odour'.
John Evelyn (1661) published the first ever written report on
air pollution entitled 'Fumifugium or the Aer and Smoke of London
Dissipated' (Elmson 1987). The first step to curb the air
pollution was taken in 1819 when a committee to investigate the
operation of engine and furnace, was appointed by parliment (U.K.
Open University, 1975). In USA, the municipal legislation prohi-
: 6 :
biting emmission of 'dense" smoke was enacted in 1881 in Chicago.
In 1952, Oregon introduced the first Air Pollution Control Legis
lation. Under the Air PolJ ution Control Act of 1947 a synthetic
rubber manufacturing plant was closed down in California. Seller
and Jones (1973^ indicated that the detei-ioration of the environ
ment was tocussed upon by the news media sometime in 1969'. This
resulted :ln the enactment of the innovative National Environmental
Policy Act (1969), and the sweeping Clean Air Amendment of 1970
(Elmson, J987).
Transfrontier pollution problems include acid rain, phol.o-
chemical oxidants (Ozone) episodes and accidental release of large
quantities) of pollutants such as ionizing radiation and toxLc
chemicals. Global problems range from build up in levels of
carbon dioxide, toxic chemicals, ionizing radiation and anthro
pogenic heat, to the depletion of stratospheric ozone. These
problems can only be solved by co-operation in undertaking effec
tive pollution control measures.
The atmospheric 'ozone layer' has a high concentration of
ozone (0^) located in the stratosphere. This 'ozone layer*
performs an important function i.e. absorbing solar ultraviolet
radiation. A reduction in this layer would result in warming of
the lower atmosphere and the earth surface. Researchers have
observed a depletion of the life protecting ozone layer over
Antarctica. Ozone depletion in certain parts of USA was found to
• 7 •
increase the level of smog and chances of acid rain. Srivastava
and Zalpuri (1988) have published results of ozone researches in
the Indian Environment. Pine trees are highly sensitive of ozone
pollution. Possible causes of ozone depletion are the products
emitted from the supersonic air crafts, nitrous oxides released
from nitrogen-based chemical fertilizers, oxides of nitrogen
produced by nuclear weapon testing, and chloroflurocarbon used in
aerosol sprays, refrigeration system and industrial processes.
Unpolluted precipetates have a pH higher than 5.6. Carbon
dioxide causes mild acidity in the atmosphere by forming caJ-bonic
acid. Human activity causes a dramatic Increase in the acidity
of precipitation at the local level and perhaps even at the (jlobal
one (Likens e^. aX* 1979). Large quantities of oxides of nitrogen
and sulphur especially SO^ and NO^ react with atmospheric moisture
tp form sulphurous acid, sulphuric acid and nitric acid. When
the acid content becomes high and pH falls down to !D, 4 or even
up to 2.5, we call it 'Acid rain'. Exceptionally low pH values
have been observed during rainstroms, eg. 2.4 value at Pilloc.hry
in Scotland on April 10, 1974 (Likens et aj,. 1979). It caused
damage to the aquatic and terrestrial ecosystems by killing huge
population of fish and leading to stock depletion in the aquatic
ecosystem, decreasing nutrient availability, mobilizing toxic
metals, leaching important soil chemicals and changing species
composition and decomposers micro-organisms in the terrestrial
ecosystem.
: 8 :
The first historical report of acid rain was by Charles
Crowther and Arthur G. Ruston (1911) who recorded a pH of 3.2
in Leeds, England. Rainfall with an acidity level of the pH
of 4.8 was recorded at Greater Bombay dvjring monsoon of 1974-
1975 (Kumar -fe Sharma, 1987).
Acid rain may lead to a direct or an indirect poisoning
through plants or insects or birds. Symbiotic relationship bet
ween certain plants and mycorrhiza forming fungus is sensitive
to acid rain input into the soil. Acid rain affects vegetation.
It destroyed various coniferous forests in Germany and Scandinavia
(Van Breeman, 1985; Paces 1985). Studies on tomatoes at Hawaii
Island indicate that low pH decreased pollen germination, pollen-
tube growth, and lowered the quality and productivity.
Many buildings and historical monuments have also started
showing significant deterioration. Acropolis in Greece, Lincoln
memorial and Cleopetra's needle in Washington are some examples.
Taj Mahal in India is experiencing corrosion and yellowing due
to Mathura Oil Refinery, releasing 5 tonnes of SO^ per day.
Concentration of sulphur dioxide would be 100 microgram per cubic
meter in Agra which is bound to play havoc with the Taj Mahal
and the Bharatpur Bird Sanctuary and the neighbouring vegetation.
Another serious type of air pollution is 'smog*. This term
was coined to denote the combination of smoke with fog, mainly
: 9 :
occurring in urban and industrial areas. The smog arising from
high sulphur fossil fuels is also called London smog. Another
type of smog comprises oxidizing compounds, primarily ozone and
oxides of nitrogen.
Smog was first noticed in Los Angeles in early 1940s, and
by 1970 large cities in Europe, Australia and Japan had experi
enced it. Smog has always been a great hindrance to human life.
On October 26, 1948, nearly 1000 people died of suffocation and
pulmonary irritation in the Danora town of Pennsylvania, U.S.A.
due to smog accumulation from H„SO. precipetate, zinc plant and
steel factory. Another smog disaster took place in London in
December 1952 in which thousands of people died. Reports of city
being smothered have also arrived from Bombay.
As to the danger of the nuclear weapons, it is suggested
that detonation of thousands of nuclear warheads would cause
extensive fires which would pour in million of tonnes of black
smoke. These fine particles would absorb solar energy and form
a dense smoke layer encircling the mid latitude of the Northern
Hemisphere. As little as 3 to 5 per cent solar radiation might
penetrate this particulate layer for several weeks after the war
resulting in darkness which would only slowly give way to gloomy
twilight conditions (Crutzen . Briks, 1982).
Growing industrialization has increased the burden of foreign
: 10 :
contaminants leading to air pollution. Carter (1985) claims
that Czechoslovakia is one of the most intensely airpolluted
countries of the world, and according to Timberlake (1981),
Katovice industrial region (Poland) near Czechoslovakia border
is the worst polluted region in the world.
The air becomes polluted because the capacity of air flowinq
over much local areas is not sufficient to dilute the contami
nants below a certain threshold. Air pollution can rarely be
traced to one pollutant, but is a mixture or combination of many
types of contaminant that include vapours, gases, droplets spores,
pollen grains, dusts, bacteria and radioactive particles. The
main contaminants are grouped as (a) the natural contaminants and
(b) those resulting from the modern industrialization. Pollen
dust is one of the natural contaminants, affecting nearly 4 million
people of North America each year, with various degrees of hay-
fever. Natural dust a mixture of solid particles, also poses a
great threat to human population. The particulate matters in the
atmosphere are classified into Aitkin nuclei (size less than 0.01
^im); fine particles (size between 0.01 ^m and roughly 3.0 (im);
and coarse particles (size greater than roughly 3.0 nm). Fine
particles of 0.1 to 2.5 \im are generated as direct combination
products and as gases, then are later transformed into the parl.i-
cles in the atmosphere. Coarse aprticles are genetared by
mechanical events including wind and friction created by tyres on
: 11 :
road; these are rich in silicate. Fine particles are more
hazardous to health than coarse particles. Large amount of dust
is emitted from various thermal electric power plants and
combustion process using low grade coals. 75 per cent of the
industrial dust (exclusive of soot) comes trom fuel combustion
(Rupp, 1965). Most electric power plants which Durn 2000 tonnes
of low grade coal a day emit about 400 tonnes of ashes and 120
tonnes of sulphurous gas every day (Astanin > Blagosklovon, 1983).
From the annual combustion of 180 million tonnes of coal in Great
Britain, 0«6 Million tonnes of ash, 2.4 million tonnes of smoke
and 5.2 million tonnes of sulphur dioxide per year are released
into the air (Metham, 1952).
The dust in the atmoshpere has a wide range of chemical
composition. Small particles, usually less than 1 micron in
diameter present in the air, are referred to as 'aerosols'.
Aerosols from 'dust' if solid, and 'mist' if liquid regardless
of the particle size (Corn, 1968). The presence of suspended
solid or liquid in a gas renders it more sensitive to thermal
radiation. Particles become warm by absorbing heat radiations
and communicate their heat by conduction to the gas immediately
surrounding them. Another toxic pollutant is PAN (Peroxy acetyl
nitrate) which is a by product of automobile exhausts.
: 12 :
Typical Diameter of Aerosol Particles
Aerosols
Tobaco smoke
NHXl smoke
H2S0^ mist
Zn 0 smoke
Coal-mine air
Flour-mill air
Cement mill (Kiln exhaust)
Grain elevator air
Fog
Talc dust
Pigments
Cement dust is a mixture of Ca, K, Si and Na oxides, and
is an important particulate pollutant. The particles of cement
ranging from 0.1 to 100 nm in size, settle on the surface of
soil and vegetation. This fallout leads to changes in the soil
characteristic and plant biology.
It is difficult to have a clear demarcation between parti
culate pollutants and gaseous pollutants. Carbon mono oxide,
carbon dioxide, sulphur dioxide, hydrogen flouride, nitrogen
dioxide and ozone are the common gaseous pollutants.
Diameter,
0.
0 .
0 ,
0 .
10
15-
10
15
50
10
1-
.25
.1
, 8 -5 .
,05
•20
•4
A
5
: 13 :
Carbon monoxide is pj-oduced by imcomplete combustion of
fossil fuels, and is highly toxic. Hoemoglobin, the oxygen
carrier, has a greater efficiency for carbon monoxide; together
they form a stable compound, carboxyl (HbCo) that decreases the
amount of combined hoemoglobin available for oxygen transport.
If the level of carboxyl increases, it may cause coma leading to
death. CO^ is another gaseous pollutant which is an important
determinant of the thermal balance in the earth atmosphere. It
is transparent to incoming shortwaves and solar radiation. How
ever, it is a strong absorber of outgoing terrestrial radiation,
thus it traps energy within the atmosphere, warms the surface
and the lower atmosphere such as the glass in a green traps the
Sun's heat (by inhibiting convection and thereby stopping the
warm air from rising and escaping); this process is known as
•Green house effect*. Hoffman and Wells (1987) have projected
future changes in green house gasses and noted that during the
course of time elapsed since industrialization, CO^ content has
risen by 2b% and may double (rising by 100%) by the middle of
the next century. There is a constant rise of C0„ content from
315 ppm or 0,0315? in 1958 to 345 ppm or 0.0345? in 1985 with a
narrow seasonal oscillation every year. The National Academy
of Sciences of USA and the U.S. Environment Protection Agency
(EPA) have made future projections of the rise of carbon in the
atmosphere. In U.S.A. alone, more than 65 million tonnes of CO
: 14 :
are emitted annually. In Calcutta city, 450 tonnes of C0„ are
discharged every day (Ambasht, 1989). Smith (1984) has quoted
Seiler (1974) to claim that the annual global input of C0„ is
14 6x10 g or 6000000000 tonnes. Most of the emission is directly
from anthropogenic operated sources. Increase in carbon dioxide
will result in the global increase in annual average temperature
leading to regional and seasonal changes. But the most benificlal
effect of CO^ enrichment was seen on plants; the crop yield enhan
ced with the rise in C0„ level. Beside CO^ and atmospheric
moisture other green house gases include chlorofluro-carbon,
methane, nitrous oxide, ozone and some other trace gases.
Other key compounds of the modern civilization are heavy
metals. When present in excess, they become toxic and may lead
to death. Their mere existance has become a threat to the
existence of countless species of plants and animals and may
ultimately threaten the very survival of the human race. Most
toxic are methyl mercury and tetraethyl lead. The natives of
modern cities (including India) afflicted by pollution are gene
rally prone to deadly disease 'minimata', the progressive symp
toms of which are madness, paralysis, loss of speech, vision and
emotional control followed by wasteing away of muscles and then
death. Minimata is related to high metal pollution. 'Plumbium'
is a disease caused by lead posioning. Its symptoms are brain
damage and various diorders of central nervous system.
: 15 :
The global anthropogenic sulphur dioxide emission is
estimated to be aproximately 75-100 million tons a year (Swedish
ministry of Agriculture, 1982). It is the second most abundant
contaminant after CO, accounting for about 20^ by weight of all
the air pollutants. The SO^ content of the atmosphere in Delhi
city had reached the level of 0.233 ppm in June 1972, whereas in
U.S.A. and W. Germany the permissible limit is only 0.1 and 0.5
ppm, respectively (Misra, 1980).
Nitrogen dioxide and Nitrous oxides are other green house
gases that are emitted from the burning of the fossil fuels.
The U.S. National Aeronautics and Space Administration (1986)
confirmed the rise of the concentration of these gases. The
current rate of increase is about 0.2? to 0.3% per year. Calcutta
city receives about 70 tons of oxides of nitrogen per day because
of industries and automobiles. Some NO^ is emitted from denitri-
fication process of manure and fertilizer. Hoffman and Wells
(1987) considered that fertilizers and other natural processes
account for 70-80^, and fossil fuel combustion for 20-30% of the
N^O in the atmosphere.
Other green house gases are chloroflurocarbons, methane,
and some other trace gases. Chloroflurocarbons (CFCs) are
chemicals synthesized by man in several industrial activities.
: 16 :
Flouride is another pollutant generally arising from
aluminium factories. It is a cumulative pollutant where concen
tration keeps on increasing in an ecosystem with time. Among
various other non-degradabJ.e pollutants are aluminium, mercurial
salt, long chain phenolic chemicals and D.D.T. Such pollutants
do not only accumulate but are often biologically magnified.
Occasionally they combine with other compounds in the environment
to produce additional toxins.
Ecological systems with significant components of lichens
and evergreen coniferous trees appear to be most sensitive t,o
air pollutants. Heck (1982) suggested that in conducting agri
cultural research we must understand the relationship between air
quality and the native agricultural plant ecosystems. Rao (1980)
enumerated the effects of air pollution (gaseous pollutants, acid
deposition and particulates) on various levels of ecosystem
organization as follows :
[aj Absorption and accumulation of pollutants in plants and
other ecosystem components such as soil and the surface and
ground water.
[b] Injury to primary producers (plants) and consumers
(animalsj due to pollutant accumulation, for example leaf
necrosis in plants and dental necrosis in animals.
Lc] Change in number, density and diversity of species and
shift in competition.
: 17 :
[dj Loss of stability and reduction in the reproductive ability
of species.
[e] Degeneration of stands and association of biotic components.
[fj Disruption of biochemical cycle.
[g] Extension of denuded and eroded area in the landscape.
The above transition in landscape from one stage to another
may take several decades depending on the load of air pollution
prevailing in the area.
There had been many lamentable incidents in the history of
human civilization which point at pollution being the main cul
prit in enabling the laying of death's icy hands on vast popula
tions.
On the calamitous night of December 3, 1984 nearly 3CXX)-
3500 people died and many were blinded, while approximately
50,000 people were left affected, suffering from multifarious
after effects due to the lekage of methyl isocynide (MTC) gas fro
the Union Carbide Pesticide Factory, Bhopal. Official sources
at a review meeting of the Indian Council of Medical Research
(ICMR) projects ar Bhopal suggested that in addition to causing
cyanide and carbon monoxide poisoning, MTC also lead to carboxy-
lation of haemoglobin by interacting with proteins in the body.
m
: 18 :
Common complaints were irritation in the eye, nausea and vomiting,
chest pain and difficulty in breathing, as MIC destroys the lung's
tissue leading to pulmonary oedema (accumulation of fluid). Vari
ous cases of mental diorder such as necrotic depression and
anxiety, neuroses and hysteria were also reported. Apart from this
at least 1,600 animals died of which were 790 buffalowes, 270 cows
483 goats, 90 dogs and 23 horses. Plants also developed lesions.
Another obnoxious example due to human error figures in
another pollution disaster in Chernobyl on the 26th April, 1986.
Here the operator misread the reactor's condition and shut off
the emergency system at the wrong moment. As a result, an
explosion produced an uncontrollable fire leading to vast quantity
of radionuclide being lifted high into the atmosphere exposing
400 million people in lb nations of Europe. Hawkes et al. (1986)
estimated the likely number of death in the Soviet Union between
5000 to 10,000. Researchers also claim that as many as a million
people in the Northern Hemisphere may develop cancer as a result
of Chernobyl accident, and half of these cancers would be fatal
(Elmson, 1987).
Plants act as an indicator of pollution, some time behaving
like sieve for dust, soot and particulates. Lichens are generally
called 'indicators of air quality or air purity*. They have a
wide range of pollution sensivity, from species like Lobarja
Dulmonaria. which are highly sensitive to Leeanora conizaeoides
: 19 :
which thrive even in the most polluted urban enviornment
(Hawksworth, 1973; Seaward; 1977). Their outer surfaces lack
waxy coating, so the SO^-rich air enters the body of lichens
freely. The algal component becomes badly affacted, especially
the chlorophyllous parts resulting into the death of lichens.
In U.K. all lichens die at 170 ig S02/m^ (0.06 ppm) level.
Injui'y caused to vegtation by air pollution has long been
recongnized. A decrease of 275 dust particulates was noted in
Hyde park London, due to green area of only 2.5 square km (see
Meetham, 1964) and 42? reduction in the total dust fall was due
to canopy of conifers in Ohio, U.S.A. (Dochinger, 1980). Many
pollutants such as ozone, sulphur dioxide and nitrogen dioxide
are toxic to plants. These pollutants, separately and together,
are responsible for at least 90? of the crop losses in U.S.A.
(Heck et JLI. 1982). The deciduous forests of Tennessee in U.S.A.
and the evergreen forests of Black Forests in Germany are being
wiped out because of SO^ pollution. In India, Maqnifera indica
is getting badly affected. A study of vegetation around coai-
depots of Varanasi indicated that many tree species around the
coal-depot were either dead or in the process of dying. In the
affected areas coal-dust is added to the soil resulting in
alteration of edaphic properties and subsequently plant growth.
The joint action of different pollutants may increase plant injury,
reduce rate of growth and biomass and decrease yield more than
! 20 :
either pollutant alone. Along a 60 km transect cown-wind from
smelter in Ontario, Canada there were no trees or shrubs in the
first 8 km, and there was high mortality of mature trees up to
as far as 25 km. The species richness of the ground flora was
reduced for up to 35 km downwind.
SOURCES OF AIR POLLUTION
The atmosphere constantly receives inputs from the natural
and man-made sources. Among the Natural Sources are gasses from
volcanoes, forest fire and biological respiration, and particu
late matters like pollen grains, bacteria, viruses, cosmic c:i\ist
from outer space and salt. Among the man-made sources are gases
from kitchen, incineration of domestic and municipal wastes,
automobiles, railways and aeroplanes, cement and metal processing
industries and coal based thermal power plants etc.
About 100 billion cycads of fine ash is thrown into the
atmosphere from a strong volcanic erruption (Kapper ^ Geiger,
1936). Tremendous quantities of gaseous impurities are emitted
from automobile exhausts. For instance, approximately 700 to
1000 tons of volatile hydrocarbons are emitted daily from auto
mobile exhausts into the atmosphere of Los Angeles (Maghill et
^.1952).
The air pollutants emitting directly from industrial tech
nology are the primary pollutants, while those formed from the
primary pollutants through atmospheric transformation are the
secondary pollutants.
The photochemical oxidants (primarily ozone - 0_) the most
important pollutants in U.S.A. and Canada are secondary pollutants
: 22 :
SO^ anci NO-, t h e p r e c u r s o r s of ac id a e r o s o l s , a r e t h e next
most impor tan t p o l l u t a n t s .
LIST OF PHYTOTOXIC AIR POLLUTANTS IN ORDER OF IMPORTANCE TO
PLANT SYSTEM
POLLUTANT PRIMARY OR SECONDARY
FORM MAJOR SOURCE (S)
SO,
NO.
HF
PAN-Oxid
Secondary Gas
Primary Gas
NO
Cl^
HCl
Toxic elements
Primary
Primary
Primary
Primary
Primary and Gas
Secondary
Primary Gas
Particulate
Primary Gas
Secondary Gas
Gas
Gas
Gas
Atmospheric transformation (asso
ciated with automotive emissions,
NO^ hydrocarbons).
Power generation and smelter
operations.
From direct release and atmospheri
transformation (high temperature
combustion from NO), fertilizer
production.
Superphosphate, aluminium
Smelter.
Combustion, natural
Atmospheric transformation (auto
motive emissions, NO^, Hydro
carbons) .
Combustion, natural
Spill, Manufacture
Burning of Plastics
Smelter, combustion process.
NH, Primary Gas Feedlot, natural
: 23 :
SO
NO,
H^S
CO.
2- Secondary Aerosol
Secondary Aerosol
Primary
Primary
Gas
Gas
Atmospheric transformation (50^).
Atmospheric transformation (N0„).
Paper production, natural
geothermal.
Combustion, natural.
The coal-based thermal power plants are highly pollutive as
they release sulphur dioxide, carbon dioxide, carbon monoxide,
fluoride and oxides of nitrogen. Thermal power stations produce
12»21 million tons of fly ash in the atmosphere of which one
third goes into the air and the rest is dumped on land and in
water (Fulekar et. aJL. 1982). According to a 1980 estimation, 13
million tonnes of fly ash, 4,80,000 tonnes of SO^, 2,80,000 tonnes
of NO^, 16,000 tonnes of CO and 5,000 tonnes of hydrocarbons are
released in the atmosphere each year by our thermal power stations
(Sharma 1986). The three power plants of Delhi (Rajghat, Indra-
prastha and Badarpur) consume 2,000-2,5000 tonnes of coal and
release 600 tonnes of fly ash daily (Rai, 1984). Each ton of
coal-ash contains seventy elements which include 70 gm of nickle,
500 gm of arsenic, 500 gm of germanium, 400 gm of uranium , 300 gm
of cobalt, 200 gm of tin, 100 gm of lead, 20 gm of bismuth and
5 gm of cadmium. Thermal plants also emit large amounts of dust.
Perhaps 7b% of the industrial dust (exclusive of soot) comes from
combustion (Rupp, 1956). Most electric power plants which burn
: 24 :
2,000 tonnes of low grade coal a day, emit about 400 tonnes of
ashes and 120 tonnes of sulphurous gas every day (Astanin
Blagosklonov, 1983).
The source of heavy metals are transport, industries, power
generation and fossil-fuel burning, whereas sources of dust
range from major emission such as dust from combustion and pro
cessing operations down to minor ones such as rubber tire dust.
DUST SOURCES
SOURCE
Combustion
Solid handling
and processing
Vapourizing
operations
EXAMPLES
Fuel burning (coal, wood fuel oil, fuel con
taining additive), incineration. Others
(tobacco smoking, forest fires).
Loading and unloading of raw material, mixing
and packing, solids size reduction (crushing
and grinding of ores, stones, cement ferti
lizers, rock), industries using solids
(metal refining, foundaries, petroleum cata
lytic cracking, roofing and wall bord manu
facture), food processing (grains, spray-
dried milk).
Petrometallurgical operations (zinc and lead
oxides from non-ferous metal processing,
silica from aluminium industry); emission of
chemical vapour (part of which later becomes
solid crystals).
: 25 :
Earth moving By constquetion and mining; by agricultural
operations operations; by nature and by transportation
(cars, human).
Others House cleaning, rubber, tire, abrasion etc.
Nearly 75 per cent of the industrial dust (exclusive oi
soot) comes from fuel combustion. Large size high volatile
coals produce little pollution whereas the low-volatile coair,
produce more carry over and fly ash.
AIR POLLUTION
Air pollution is a product of the activities of man. As
man manufactured chemicals and metals, generated electrical
powers and developed transportation, the problem of air pollu
tion became inevitable.
Air pollutants are classified in a variety of ways.
Broadly, they are categorised as (1) primary pollutants and
(2) secondary pollutants.
The primary pollutants comprise compounds of sulphur, nitro
gen and flouride, while the secondary pollutants develop by the
combination of reactions of primary pollutants with indigenous
aerial material or photolytic activities. This group includes
harmful combinations of mettalic compounds and water vapour,
photochemical pollutants of ozone and homologous series of peroxy-
acetyl nitrate etc.
Burning of coal gives off soot and S0„. Chemical industries
release HCl, H„SO,, S0_, NO and other gases into the atmosphere.
Petroleum industries release hydrocarbons, SO^, N0_ and other
particulate matters. The metallurgical industries add quantities
of lead, arsenic, zinc, copper and cadmium in the air. The
automobiles are the biggest pollutars, pumping carbon dioxide,
: 27 :
oxides of nitrogen, soot, lead and several other noxious
compounds. In India, which has a vast reserve of coal, thermal
power plants contribute a lot to the atmospheric pollution.
According to 1980 estimates, 13 million tonnes of flyash,
4,80,(XX) tonnes of SOg, 2,80,000 tonnes of NOx, 16,000 tonnps of
CO and 5,(XX) tonnes of hydrocarbons are released in the atmos
phere each year by out thermal power stations (Sharma, 1986).
Annual emissions of SO^ and N0_ are estimated to be 50x10
and 30x10 tonnes, respectively, in North America and Europe.
Ambient air concentration of SO,, and NO,, may occasionally reach
peaks between 0.03 and 0.15 ppm. in urban areas. In India, the
pace and magnitude of the industrial changes have a far reaching
impact on the environment which is being increasingly polluted
(Hemalatha, 1983).
OZONE (0^) : Photolytic reactions in the polluted atmosphere
are the major sources of phytotoxic levels of ozone. Hydrocarbons
and oxides of nitrogen emmitted from automobile and inoustries
transform into ozone. The photochemical reactions between pinene
and nitrogen dioxide can produce 0^ and peroxyacetyl nitrate
(Stephen -^ Scott, 1962). The natural background concentration of
©2 is between 10 and 40 ppb, although it may reach 80 ppb or more
after a localized incursion of stratospheric air (Derwent et al.
1978). In British Isles, the potential for the formation of photo-
: 28 :
chemical ozone in phytotoxic concentrations occurs throughout
the country (Ashmore, et a2« 1980). Nonurban air contains
smaller amounts of compounds that react with ozone, so ozone
can persist for long in the rural area (Coffey et al. 1977;
Cleveland ei aJ,. 1977; Wolff et 3 1. 1977; Isaksen, et al. J 978).
S0„ : Sulphur compounds are released into the atmosphere by
both natural and anthropogenic sources. Sulphur dioxide is
produced during the combustion of sulphur-containing fuels such
as coal and oil, heating of sulfide ores during smelting, and
production and use of S, H^SO., petroleum and the natural gas.
The burning of coal and other fuel in stationary installa
tion produces the largest quantity of S0„, some 26.5 million tons,
in 1970, in the U.S. (Dochinger •' Calvert, 1978). Matham (1952)
calculated that from the annual combustion of 180 million tons
of coal in Great Britain, 0.6 million tons of ash, 2.4 million
tons of smoke and 5.2 million tons of sulphur dioxide were relea
sed per year. Annual emission of SO^ in North America and
Western Europe is 50x10 tonnes (Unsworth-^ Ormord, 1982). In
June 1972, the SO^ content of the atmoshpere in Delhi reached
the level of 0.233 ppm whereas in U.S.A. and West Germany the
permissible limit was 0.1 and 0.55 ppm respectively. In India
about 80 million tons of coal is burnt annually. The daily
average consumption coal in Obra Thermal Power Plant, Mirzapur
: 29 :
is about 9,120 metric tons, and the expected emission of sulphvir
in the area may range trom 45.6 to 182.4 metric tons per day
(Rao et. .ait 1985).
CO2 and CO : CO^ is ejected into the atmosphere by volcanoes,
decay of organic matter, consumption of coal and petroleum, and
destruction of forests which have a great CO^ absorbing capacity.
The annual global-emission ratio of C0_ from fossil-fuel
burning reached 5.3 Gt of C0_ per year in 1980 (Clark _et al.
1982). The annual production of C0„ by respiration and decay
is approximately 0.040 g/sq. cm/year. Over the entire surface 18 11
of 5.1x10 cm, there is production of 2x10 metric tons of CO^. Concentration of CO2 in the air of industrial areas is at times
as high as 600 ppm (Cholak, 1952).
Carbon monoxide is produced as a result of incomplete
14 combustion. About 6x10 gm of carbon monoxide is annually
discharged into the atmosphere (Seller, 1974). Most of the
anthropogenic emissions are concentrated in the temperate lati
tude of the Northern hemisphere-.
NO : Both natural (forest-fire, high temperature, soil
microbiological action) and human activities (motor, oil well
fires, burning of fossil fuels and nuclear detonations) contri-
: 30 :
bute to NO polluted atmosphere. Low altitude detonation of
32 one mega ton nuclear device release 1x10' molecules of NO.
Coal burning alone accounts for 80^ of NO in the atmosphere
(Morrison, 1980), Transportation contributes to about 30% of
NO2 emission in U.K. and West Germany, 40? in Japan and 45% in
U.S.A. Hutchinson (1944) estimated a biological fixation at
0.07 mg of nitrogen per square centimeter of earth's surface per
year and non-biological fixation at not more than 0.0035 mg/sq
cm/year. Much of the nitrogen is returned back to atmosphere
by the decay of organic matters.
In a most extensive survey in Britain at a rural site
remote from the sources of NO, Martin and Barber (1981) found
50% more NO than SO^ on a volume/volume basis. Law et. al. (L982)
claimed that the concentration of NO would rise to nearly 2000
ppb in the absence of uptake by a crop. According to estimate
made in 1981, the level of NO2 in Delhi was 23 tig/m in resi-
3 3 dential area, 32 ig/m in commercial area and 27 |ig/m in
3 3 industrial area, while it was 62 |ig/m in Bombay and 74 g/m in Ahemdabad.
Flouride : Flouride occurs in a wide range of the Natural
materials such as coal, clay, mineral ores, and may be released
on heating or burning at high temperature. Although coal
contains relatively little flouride (about 0.01-0.08%), the bulk
: 31 :
of coal burnt annually is so heavy that the quantity of
flouride derived from their source is immence. In Czechoslovakia,
where average flouride content of coal is as low as 0.04^, more
than 10,000 tons of flouride is released annually in the atmos
phere.
Hydrogen flouride is another important pollutant released
in the combustion process of the fossil fuels, aluminium
industries and phosphate-reduction plants.
Lead : The main source of lead in the atmosphere is automobile
fuel, to which it is added as an anti-knock agent. Other sources
of lead are various industrial and agricultural activities viz.
manufacturing processes, incineration of refuse and combustion
of coal. After combustion much of this lead (70? ) is transmitted
via the exaust to the atmosphere as particulate of lead halide,
or complexes of ammonium halide (Hirscher € Gilbert, 1964;
Heichel € Hankin, 1972).
AIR POLLUTION IMPACTS ON PLANTS :
The damaging effects of air pollutants on vegetation have
long been recognized (Das^Gupta, 1957; Stern, 1968; Woodwell
1970; Mudd 4r Kozlowski, 1975; Treshow, 1984).
Interest in air pollution injury to crop is increasing in
the tropical agricultural areas as newly developed industries
and urbanistation have resulted in an increased concentration
of phytotoxic air pollutants (Balasubramanyam, 1957; Street e;t,
a^. 1971; Chaphekar, 1972; Deoras, 1977; Rao, 1977; Valenzona
et al. 1978). Studies on mixture of pollutants are becoming
more important due to recognition of the heterogenous composi
tion of ambient air and their interactive effect on plants
(Lefohn - Ormrod, 1984).
Vegetation is most sensitive to gaseous pollutants than to
aerosols. Many plant species and varietes exhibit differing
degree of sensitivity to different air pollutants. The wide
spread forest-decline in Europe and North America occurred due
to air pollution. In Varanasi (India), several trees were
damaged due to coal dust (Rao, 1980). Plants near power station
also exhibited a decline due to decrease in pH and increase in
sulphur and potassium contents of the soil and leaf tissue.
: 33
Responses of vegetation to air pollutants are variable
depending upon both external and internal factors. They usually
sharpen with increasing ambient concentration of pollutants.
On the basis of their responses to pollution under field condi
tions, plants are classified into sensitive and tolerant species
(Jacobson - Hill, 1970). Some of the severely affected trees by
air pollution are Norway spruce (Pinus abies Karst). silver fir
(Abies alba Mill), Scotch pine (Pinus sylvestris L.), larch
(Larix dgcidue L.), peech (Faqus svlvatica L.), maple (Acer
plantinoides L.) and oak (Quercus robur L.) (Scholz, 1984).
In many developed countries vegetation was found to f1 Iter
out dust, soot and particulates from the atmosphere. Dochlnger
(1980) found a reduction up to 42? in the overall dustfall by a
canopy of the coniferous plants in the urban area of Ohio, U.S.A.
Large sized leaves as those of Calotropis procera collected
maximum amount of dust, while Eucalyptus citriodora and Acacia
monilifornus. both with oblanceolate to lanceolate leaves,
collected the minimum amount of dust (Yunus et_ a_l. 1988).
The joint action of different pollutants reduced the rate
of growth. This may not be accompained by expression of any
visual symptom possibly due to several pre-visual disturbances
in the metabolism (Malhotra ^ Sarkar, 1979; Ayazloo jet ad. 1980).
The growth losses were considered to be the result of the
cumuj-ative effects of the periodic peaks (Godzik >«= Kurpa, 1982).
: 34 :
Multiple exposures of plants to relatively low pollution con
centration which may fluctuate are called chronic exposures.
These were more prevasive and more liable to produce effect on
growth without showing obvious symptoms of injury. It was also
confirmed by Musselman ejt . (1983) in kidney bean that episo
dic exposures were more injurious than constant exposures.
Air pollution retarded growth in pine trees (Astanin
Blagosklonov, 1983), Glycine max (Mishra -& Shukla, 1986). Plnus
nigra (Gabor, 1987). Silene cucubalus wib (Ducek et. al, 1987),
Melilotus indica (Ghouse -fe Khan, 1983), Anaqallis arvensis and
Melilotus indica (Ghouse A; Saquib, 1986). It causes decrease
in the plant height in Zea mays and Glycine max (Mishra -^ShukLa,
1986), Phaseolus aureus (Prasad - Rao, 1981) and Polygonum
glabrum (Khan -€: Khair, 1984). Only shoot length was reduced in
Commelina benghalensis (Mishra, 1982) and in Acalypha hispida,
Ceratophvllum hortaenge. Malva viscus Canzati, Nerium indica.
Pothos scandens. Quisquatis indica and Tabernaemontana (Salgare '.
Chakraborty, 1988).
Air pollution decreased in dry matter of shoot in Acalypha
hispida. Malva viscus Canzati, Ceratophyllum hortaenge. Nerium
indica. Pothos scandens, Quisguatis indica and Tabernaemontana
(Salgare ^Chakraborty, 1988), but an increase in dry matter
accumulation in Croton bonplandianum (Pandey, 1989). Biomass of
: 35 :
plant decreases due to air pollution in Clcer arietinum,
Dollchos lablab. Lens culneris, Phaseolus aurens. Vlqna
simensis (Varshney ^ Gaxg, 1980) and Desmodium triflorum
(Khan ^Khair, 1985).
Changes in biomass are critical to assesment of long
term effects of pollutants on plants. EJiomass measurement;;
permit studies of growth rate, correlation with injury and
other characteristics studies.
It was postulated that lack of normal vigorous growth
causes early leaf fall, reduction in size of fruit and leaves
and poor growth of plant (Amani, 1982b; Ghouse -4: Khan, 1983,
1984; Khan J&;Khair, 1985a, b).
In case of Cassia occidentalis (Amani et_ . 1979), air
pollution caused an increase in the size and weight of the
whole plant, shoot, root, leaves and fruits.. Plant to plant
variation occurs due to species, cultivars and individual plant
differences and soil plant atmosphere variations due to tempe
rature, water status, irradiations, ventilation, oxygen and
carbondioxide status.
Leaf surface traits were sensitive to air pollution and
their responses could be used as an indicator of the pollution
(Ahmad ^Yunus, 1985). Leaves constitute the most important
: 36 :
part of plant for trapping the solar radiation, and air pollu
tion affects the plant system directly through leaf surface.
Varshney and Garg (1980) studied the relationship between leaf
surface characteristics and susceptibility of plants to air
pollution and concluded that plants with pilose and pubescent
leaf surface were more affected as compared to plants with
glabrescent leaf surface.
Leaf area is most important for determining the poto-
synthetic ability of the plant community. The ecological
significance of leaf area is due to its chlorophyll content
that forms the basis of dry matter production in plants. The
enormus leaf area acts as a natural sink for pollutants. A
decrease in leaf area and leaf biomass in response to air pollu
tion was found in Cicer arietinum. Dolichos lablab. Lens cul-
heris. Phaseolus aurens. Viqna simensis (Varshney ^ Garg, 1980)
and a reduction in leaf area only occurred in Commelina
benqhalensis (Mishra, 1982), Polygonum qlabrum (Khan ^' Khaii,
1984), Azadirachta indica and Manqifera indica (Dubey _et al.
1984) and Desmodium trif lorum (Khan J- Khair, 1985). Howevei ,
Clerodendrum indicum (Dubey ejt a^. 1984) showed little effecto
The difference in the amount of deposition may be attributed to
the nature of leaf surface (Little, 1977).
The number of leaves reduced in Phaseolus aureus (Prasad 4-
Rao, 1981). Also, the length of petiole, length of lamina
37 :
breadth of lamina, length/breadth ratio, calculated area,
moisture content, dry matter content and dust fall got reduced
in Acalypha hispida. Malva vlscum Conzati, Cerotophyllum
hortaenqe, Nerium indica. Pothos scandens. Quisquatis indica
and Tabernaemonatana (Salgare ^ Chakroborty, 1988). Leaf deve
lopment was retarded due to air pollution in Ahaqallis arvensis
and Melilotus indica (Ghouse J^ Saquib, 1986). Pueraria lobata
showed decrease in the leaf length, leaf width and petiole length
in response to air pollution (Sharma £t aJ. 1980).
Leaf longevity is also affected by air pollution, thus
causing a variety of consequences on growth. Chronic injury
takes many forms including early senescence of leaf tissue.
Early defoliation was found in Pinus nigra (Gabor, 1987),
Dactvlis qlomerata and Loqium perenne (Ashenden, 1987).
Several workers have worked to establish the concept of
using leaf cuticular features as indicators of air pollution
(Sharma '; Butler, 1973, 1975; Sharma -& Tyree, 1975; Sharma, 1977;
Wagoner, 1975; Godzik 4r Sassen, 1978; Garg -^Varshney, 1980).
Leaf surface characters including cuticular and epidermal
features can be used as bio-indicators because they respond to
air pollution in a predictable way. Usually only quantitative
changes are induced due to stress of pollution and one rarely
across qualitative changes in the micro morphological parameters
(Yunus ^ Ahmad, 1983).
: 38 :
Air pollution increased stomatal density in Syzygium
cuminii (Jafri et_ al. 1979), Psidlurn qu.lava (Yunus A Ahmad,
1980), Tabernaemontana coronaria (Srivastava jet. . 1980),
Calotropis procera (Yunus Xc Ahmad, 1981), Croton sparisiflorus
(Srivastava ^Ahmad, 1982), Ipomea fistulosa (Yunus et. ad. 1982)
and in Manqifera indica. Ai'tocarpus inteqrlfolia. Ficus benqha-
lensis and Psidium quiava (Debnath -2r Nayar, 1983). Rao (1979)
postulated that plant responses to pollutants may also depend
upon its internal conditions (Rao, 1979). For example, when
stomatal density and relative water content are high nutrient
uptake is optimum and ascorbic acid content is low, then the
plant response also increases vice versa. While Sharma (1975)
suggested that decrease of stomatal density limits gas exchange
and thereby reduces exposure of moist, more susceptible inner
leaf surface to the injurious pollutants. The stomatal density
decreases in (Croton bonplandianus) (Zaidi et. ad. 1979).
Pueraria lobata (Sharma et. jal. 1980), Commelina benqhalensis
(Mishra, 1982), Altermanthera sesilis, Aqeranthum conyzoideti.
Amaranthus spinosus, Blumea eriantha. Cassia tora. Eclipta
erecta. Euphorbia hirta. Heliotropium indicum and Malachea
capitata (Salgare . Acharekar, 1988). In case of Catharanthus
roseus and Lantana camara (Salgare ^ Chakroborty, 1988), how
ever, stomatal frequency of lower epidermis was not inhibited.
There was no remarkable change in either frequency or size of
stomata in Alistonea scholaris, Ficus reliqiosa. Mimusops elenqi.
: 39 :
Polvalthla longlfolia and Syzyglum j ambos (Debnath ^ Nayar,
1983).
Yunus £t al, (1979) stated that stomatal openings were
larger and cuticular striation more conspicuous in leaves of
the polluted plants than in those of healthy ones.
The size of stomatal pore increased in many species such
as Ricinus communis (Yunus et. aj.. 1979), Ipomea f istulosa (Yunus
et al. 1982), Artocarpus inteqrifolia. Fieus benqhalansis.
Manqif era indica and Psidium qui ava (Debnath - Nayar, 1983).
On the other hand, decrease in size of stomatal pore was recorded
in Brassica oleraceae. Chenopodium albtjm. Cicer arietinum.
Dollchso lablab. Lantana camara. Sonchus asperthia and Withfyaa
siminefera (Garg ^ Varshney, 1981) and Commelina benqhalensls
(Mishra, 1982). The decrease in size of stomatal pore was a
feature adopted by many plants to resist pollution; the decreased
stomatal pore could reduce the rate of entry of pollutants Into
the plant (Levitt, 1972, 1980).
Plants from the polluted environment show morphological
changes in trichomes (Sharma >fe Butler, 1975; Varshney -^Garg,
1980). These characteristics may regulate the leaf connectivity
and latent heat of vaporization.
An increase in trichome number in response to air pollu
tion was found in Svzraium cuminii (Jafri et. . 1979), Psidium
: 40 :
qusLJana (Yunus ^ Ahmad, 1980), Callistemon citrlnus (Ghouse et_
ajL. 1980), Tabernaemontana coron^rla (Srivastava et., a^. 1980),
Calotropi$ procera (Yunus Ahmad, 1981), Brasslca oleraceae.
Chenopodlum album. Cicer arletinum. Pollchos lablab. Lantana
camara, Sonchus asperthia. Withania slmlnif era* (Garg -4r Varshnpy,
1981), Croton sparsiflorus (Srivastava-*^ Ahmad, 1982) and I pome a
fIstulosa (Yunus e^ aj,. 1982).
Increase in size and number of trichomes per unit of leaf
area occurs in Croton bonpJandianus (Zaidi _et. al, 1979) and the
length of trichome increases in Croton bonplandianus (Amani, t
al. 1979), Pueraria lobata (Sharma et jy., 1980), Comrnelina
benghalensis (Mishra, 1982), Ficus benghalensis (Gupta Ghouse,
1987) and Tridax procumbens (Gupta •- Ghouse, 1988). However,
in Psidium quiava (Yunus Ahmad, 1980), the trichome size
decreases on exposure to air pollution. Subsidiary cells consis
ting of two cells remained unchanged in Pueraria lobata (Sharma
et . 1980;.
In case of Brassia oleracea. Chenopodium album. Cicer
arletinum. Dolichos lablab. Lantana camara. Sonechus asperthia
and Wilthania seminifera (Garg -^Varshney, 1981), folding on
subsidiary cells at the aoaxial leaf surface increased in
response to air polution. Air pollution increased length breadth
and area of stomata and stomatal index in Catharanthus roseus
and Lantana camara (Salgare € Chakaraborty, 1988).
: 41 :
However, it inhibited length, breadth and area of stomata,
length/breadth ratio and the stomatal index in Aeqerantum
conyzoides, Altermanthera sessilis. Amaranthus spinosus. Blumea
eriantha. Cassia tora. Eclipta erecta. Euphorbia hirta,
Heliotroplum Indicum and Malachea capitata (Salgare ' Acharekar,
1988). Ambient air results in low frequency of epidermal cells
in Psidium qua.lava (Yunus -4 Ahmad, 1980) and Peristrophe bicaly-
culata (Inamdar Jc Chandhari, 1984). But the number of epidermal
cells per unit area increased in Syzyqium cuminli (Jafri et_ al.
1979), Tabernaemontana coronaria (Srivastava e_t al. 1980),
Calotropis procera (Yunus -4 Ahmad, 1981) and Croton sparsiflorus
(Srivastava Z; Ahmad, 1982). In Pc\rtrophe bicalyculata. increase
in size of cystolith and abnormalites in stomata were observed
(Inamdar ^Chandhari, 1984).
The air pollution effects are devided into 'Acute effects'
and 'Chronic effects'. Exposure to high concentration over short
periods causes acute effect, while exposure to low concentiat ion
over a long period results in chronic effect. The acute eftects
are celarly visible eg. chlorosis and necrosis of leaf tissue,
and chronic effects appear as retardation or disturbance of
normal growth and development or show discolouration.
Air pollution results in foliar injury of plants (Chaphekar,
1972, 1982J Banerji -^Chaphekar, 1978), as in Dalberqia sissoo
: 42 :
and Azadlrachta indlca (Kumawat -^ Dubey, 1988), in the form of
chlorotic and necrotic patches. Air pollution causes chlorotic
mottle and tip necrosis in Pinus blanksjana and Pinus strobus
(Armantano -SrMenges, 1987), necrotic lesions in Pisum sativvi;n
(Young >6 Mathew, 1981) and Nicotiana tobaccum (Acjcock, 1982),
chlorosis and tip burning (Agarwal -^Narayan, 1988) and leai
deformation in Glycine max cult Davis (Norby -2r Luxmoore, 1983).
Little is known regarding the effect of air pollution on
the anatomical features of plants. The ambient air pollution
increased the frequency of vessels in Ficus benqalensis (Gupta -
Ghouse, 1987) and reduced vessel size in Polygonum qlabrum (Khan
et al» 1984), Chenopodium album (Ghouse et al, 1985), ^ida
spinosa (Mohamooduzzafar et ail. 1986). Patura inoxia (Iqbal eJi.
al. 1986) and Cassia occidentalis (Iqbal ejt aj.. 1987). However,
the vessel length increased on exposure to ambient air pollution,
in Lantana camara (Iqbal et, ^ . 1987). Increase in the vessel
width occurred in Sida spinosa (Mahmooduzzafar et. al. 1986) and
both vessel width and vessel number increased in Cassia
occidnetalis (Iqbal ejt al.. 1987), and Achyranthes aspera
(Mahmooduzzafar ejt jj.. 1987). In Cassia tora, vessel width and
vessel area increased (Iqbal et. a_l. 1987).
Air pollution increased pore frequency in Polygonum
qlabrum (Khan jei al.. 1984), Calotropis qiqentia (Iqbal et_ al.
: 43 :
1986) and Lantana camara (Iqbal et ad. 1987) and pore area in
Achyranthes aspera (Mahmooduzzafar et aj,. 1987). However, a
decrease in pore width and total pore area was found in Polygonum
qlabrum (Khan £t al* 1984). Chenopodium album (.Ghouse et_ al.
1985) and Lantana camara (iqbal et aj,. 1987).
Similarly, length of fibres increased in Calotropis
giqentia (Iqbal et. al.. 1986), Achyranthes aspera (Mahmooduzzafar
et al. 1987), Lantana camare (iqbal .et a_l. 1987) and Ca.janus
caian (Ghouse .et. aj.. 1989), whereas it decreased in Chenopodium
album (Ghouse .et. aX» 1985), Sida spinosa (Mahmooduzzafar et_ al.
1986) and Cassia occidentalis (Iqbal £t aj,. 1987).
Air pollution causes an increase in proportion of cortex
and xylem in Sida spinosa (Mahmooduzzafar .et ajL. 1986) and
Achyranthes aspera (Mahmooduzzafar et a_l. 1986). But in IJatura
loxia (Iqbal ejt .al.. 1986) and Lantana camara (Iqbal et. .gj,. 1V87)
proportion of cortex was relatively small. In Chenopodium c;lbum
(Saquib et aJ,. 1986), xylem area was more severly affected followed
by the pith and cortical regions.
^^ Chenopodium album (Ghouse et ^ , 1985) and Ca.lanus
ca1 ans (Ghouse et, ^» 1989), the proportion of xylem, cortex and
pith was smaller in plants exposed to air pollution.
In Calotropis giqentia. cell size and proportion of
different tissue systems were reduced (Iqbal et. .a.1. 1986). In
: 44
Manqlfera indica, conducting region of the phloem was reduced
(Ahmad J? Khan, 1986) but area, length and width of the ray across
the radial system of bark were greater under the polluted atmos
phere (Kalimullah ^ aj.. 1987); the number of ray parenchyma
cell was counstant (Kalimullah et. aj . 1988).
Air pollution caused loss of wood formation in Tectona
qrandis and Dalberqia sissoo (Ghouse _et. al. 1984). It also
affected bark components in Delonix reqia and Tamarindus indica
(Ahmad i Kalimullah, 1988).
There are many outstanding reviews outlining the pollutional
effects on the physiology of plants. These reviews cover acidic
precipitate (Evans, 1982, Jacobson, 1982; Irving, 1983)^ flourine
(Davison 1982; Weinstein Alscher-Herman, 1982), nitrogen oxides
(Mudd, 1982; Schneider '. Grand, 1982), Ozone (Jacobson 198'.!h,
Tingey J&--Taylor, 1982), Sulphur oxides (Black, 1982; Gozik -
Kurpa, 1982; Mudd, 1982; Koziol >?::Whatley, 1984; Kennenberq,
1984; Roberts, 1984; Winner et al, 1984) and pollutant mixtures
(Ormrod, 1982; Lefohn X Ormrod, 1984).
Pollution can cause an increase or decrease in transpira
tion which leads to alteration of leaf energy balance. The
pollutants can alter conductance, and water use efficiency of
paints changes.
A decrease in the rate of transpiration was found in wheat
: 45 :
(Singh i Rao, 1981), Phaseolus aures (Prasad ^ Rao, 1981),
Cassia siamea and Melia azadirachta (Kumarvat J Ducey, 1988).
Photosynthesis was decreased in Phaseolus vulgaris (Daly et_ al»
19SS) on exposure to air pollution* The depression in photo
synthesis is due to the disruption of the chloroplast membrane
and the recovery is a consequence of homeostatic processes
repairing the altered chloroplast membrance (Tingey-4 01szyk,
1985). Alteration in stomatal conductance also affects photo
synthesis.
Amount of chlorophyll in plant gives the measure of its
productive potential. Rao (1979) studied changes in chlorophyll
content. A variety of air pollutants exert their deletrious
effects on chlorophyll by converting it to chlorophyllids by
deleting the phytol group (Malhotra, 1977) or to phaeophytin
by splitting Mg " (Roberts, et al. 1971; Inglis •^. Hill, 1974;
Hallgren -4 Huss, 1975;. Chlorophylla was more susceptible than
chlorophyll b and therefore chlorophyll a/b ratio was quickly
altered (Arndt, 1974; Horsman ^Wellburn, 1975).
The ambient air causes a decrease in chlorophyll content
(Rabe, 1981) in a number of species such as Posidomia oceamica
(Augier ^ Mandinas, 1979), Triticum aestivum (Singh -^Rao, 1980),
Cicer arietenum. Dolichos lablab. Lens culnaris. Phaseolus
aureus and Viqna sinensis (Varshney iJ-Garg, 1980). Young spruce
: 46 :
barley and alfalfa plant (Rabe 4 Kreeb, 1980), Betula pandula
and Cernus sanqina (Braun e.t aj,. 19EJ0), Phaseolus aures (Prasad
Z. Rao, 1981), Manqifera indica (Pawar, 1982; Pawar ^ Dubey,
1982), ButQa monosperma (Singh, 1982) maize and soyabean (Mishra
- Shukla, 1986), winter barley (Borka, 1986), Cassia siamea,
Mella azedarach:' and Dalberqia sissoo (Kumarvat -f Dubey, 1988),
/Vzadirachta indic^. Plthecloblum dulce. Ipomea aaua tica.
Bouqalnvlllea spectabillis. Trjdex procumbus. Parthenlum hystero-
phorus (Raza Ahmad, 1988), Amaranthus spinosa. Altermantha
sessilis, Aegerantum conyzoides. Blumea eriantha» Cassia tora.
Euphorbia hirta. Eclipta erecta. Helltopium indicum and
Malchra capltata (Salgare JSlr Acharekar, 1988) ana Croton bonplan-
dianum (Panda, 1989).
Changes in soil factors and in ecophysiological characters
of plants, including N, P, K, and S content of soil and leaf
take place due to the action of air pollution. The accumulation
of N, P, K, S and Ca in Phaseolus aures (Prasad - 'Rao, 1981)
and foliar tannin content in Cryptomeria j aponica are decreased
(Terutaka £t. . 1989). An increase in sulphate content occurrea
ii Croton bonplandianum (Panda, 1989).
Studies have been made on the effect of air pollution on
activities of enzymes such as peroxidase (Nandi jet. ed. 1980,
1984, Eckert Horston, 1982), Catalase (Nandi et ed. 1980, 1984)
: 47 :
and acid phosphate (Malhotra - Khan, 1980; Eckert -& Horston,
1982).
In general, peroxidase and catalase activity was increased
by exposure to air pollutants (Curtis -^Howell, 1971, Wakinchi,
et al. 1971). Catalase activity was increased in Croton bonplan-
dianum (Panda, 1989). The activity of enzymes G6 PbH [Glucose-
6-phosphate-dehydrogenaseJ, IcDH [isocitratedehydrogenase], GDH
[Glutamate dehydroge nase], AST [Aspartate amino transferase] arid
ALT [Alanine amino transferase] has been noted to increase (Rabe,
1981).
Ascorbic acid content is also affected by air pollution
(Rao, 1979, 1981); a decrease in ascrobic acid content, carbohy
drates, and protein content was observed in Phaseolus aures
(Prasad >?:.Rao, 1981) while the ascorbic acid, relative water
content and leaf extract pH were increased in Azadirachta indica
Bouqainvilla spectablllis. Ipomea aquatica, Tridex procumbus,
Pltheclobium dulce, and Parthenium hysterophorus (Raza Ahmad,
1988).
Plants having high ascorbic acid content were less sus
ceptible to SO2 pollution (Rao, 1979, 1981). The ambient air
also changed protein quality in Festuca elatier, Quercus rubra.
Pinus toeda and Ulmus primita (Ruffin et ^ . 1983), protein
: 48 :
content (Robe, 1981), protein and RNA content in Betula pandala
and Cernus seaauina (Braun et &1. 1980).
In Pinus svlvestrls, under the impact of air pollution,
seeds accumulated high concentration of lead, zinc, cadmium,
copper, iron and calcium etc. (.Palowski, 1986). In Quercus
monqolica (Arzhanova - Elaptevskii, lySSj, accumulation of h ad,
zinc, cadmium was related to air pollution. Low contents ot
calcium, magnesium, manganese and zinc and strage wax incrusta
tion and gypsum crystal were found in the polluted needles of
Norway spruce ^Nebe _et. aJL. 1988).
Leaves of Syzyqium cumini and Tamarlndus indica show v.uied
changes in chloroplasts, in presponse to air pollution, such as
(l) varied size and shapes of chloroplasts (2) wide loucli ol
grana thylakoid, (3) long and narrow protuberences of plasti<Js
(4) loss of outer envelops of chloroplasts (5) vaculation in the
stroma (6) emergence of lipid bodies out of the chloroplast and
(7) release of stroma as free bodies in the cytoplasm (Patel -
Devi, 1986).
Leaves of Streblus asper affected by air pollution show
chloroplasts that are spherical, lobed or lens shaped with
spherical starch grain, irregular outline, dense stroma, swelling
of thylakoids, accumulation of electron dense material in the
thylakoids loculi, vacuolation in the stroma, plastoglobuli and
: 49 :
and long narrow protuberence in the cytoplasm, poorly developed
cristas in mitrochondria, hypertrophied dictyosomal vesicles and
dilated cristenae of endoplasmic reticulum (Patel-4^ Devi, 1984).
Indirect studies support the theory that primary site of
action of cjaseous pollutants is the membrance structure which
results in the Alteration of its function (Rabe -€: Kreeb, 1980}
Tanaka - Sugahara, 1980).
Air pollution directly or indirectly modifies the trophic
relationship between fruit, leaf and results in a loss of yield.
The yield of crop plants is also affected due to alteration in
their phytosynthetic activity and growth. Exposure to the
ambient air reduced the yield (Banerjee - Chaphekar, 1980;
Chaphekar 1972, 1982) in wheat (Singh -^Rao, 1981), Abelmoschus
esculentus (Gupta £fGhouse, 1986), winter barley (Borka, 1986),
maize (Anda 1986), leaf lettuce, green onion, turnip and beet
(McCool, e_t jal. 1987), and Dactylis qlomerata and Lolium perennu
(Ashenden, 1987).
Air pollution reduced flower size, pod size and fruit size
in Pueraria lobata (Sharma ejt aj.. 1980) and Gommelina benqalensis
(Mishra, 1982). In winter barley, number of flowers and size
of spikelets were reduced and fertilization was disturbed
(Borka, 1986).
Varshney and his collegues studied the impact of air
: 50 :
pollution on pollen germination and fertilization (Varshney ^
Garg, 1979; Garg i Varshney, 1980; Varshney i, Varshney, 1981).
Air pollution deteriorated fertilization in maize (Palowski,
1986) and inhibited germination in Pinus sylvestris (Palowski,
1986) and also germination and tube growth both in Gliricidia
sepium (Salgare ^ Rane, 1988), Allamanda cathartica and Cassia
siamea (Salgare . Sebastian, 1988) and Catharanthris roseus
(red flower) (Salgare X. Sebastian, 1988) and showed significant
loss to the productivity, size, frequency and viability of
pollen in Hamelia patens (Salgare <?. Sebastian, 1988).
Air pollution suppressed fruit setting in Desmodium
trif loreum (Khan Khair, 1985) and Abelmoschus esculentus
(Gupta J. Ghouse, 1986). Number of flowers in Aealvpha hisplda.
Malvaviscus cozata. Ceratophyllum hortaenqe. Nerium indica and
Tabernaemontana (Slagare J Chakarborty, 1988), and number oi'
fruits in Acacia arabica and Delonix reqia (Pawar, 1982) were
reduced.
Air pollution deteriorates seed viability in Cassia toia
and Cassia occldentalis (Krishnayyar 4> Bedi, 1986). The organic
contents of seeds were inhabited in response to air pollution
in Acacia aurieuliformls. Cassia siameat Cebla pentandra, Delonix
reqia. Erythrine indica, Glyceridia sepium. Lenaeena leucocephala,
Polyalthia lonqifolia. Sapthathodea companulata and Thesperia
populnea (Salgare Anis, 1988).
GARBONDIQXIDE
Carbon dioxide is a colour less and oduriess gas and a
normal component of air forming a constituent of the carbon
cycle in the biosphere. When at a normal concentration, it
is not considered a pollutant, but it behaves like a pollutant
at a higher concentration.
Carbon dioxides is stored in lime stones and dilomites.
A large quantity of CO2 is emitted into the urban air due to
the combustion of coal, air and gosoline. Carbon dioxide
enrichment caused a general warming of the northern hemisphere
which was first recorded in 1900 and 1940.
Less than half of the carbon dioxide is taken by the
ocean and biosphere (Sundaram, 1977). By doing this, oceans
become more acidic and lead to alteration of biological produc
tivity and albedo (Sundaram, 1977).
Carbon dioxide concentration away from the urban activities
was found to range between 303 and 220 ppm on a dry gas basis
(Keeling, 1961), the concentration could go up to 600 ppm in
the air of the industrial area (Cholak, 1952).
Carbon dioxide concentration varies with season as well
as during day and night. It tends to be the maximum at night
: 52 :
when photosynthetic level declines to a minimum but decompo
sition and respiration of organic matters enhance the rate of
CO^ formation, and minimum in the afternoon hours when photo
synthesis is at its maximum. Seasonal variations in CO^ con
centration owe to the seasonal biological fluctuations (Tabb(>ns,
1968).
Robinson (1968) observed that there has been a steady
increase in the atmospheric CO^ concentration, since around
1900. Prior to 1900, the concentration was about 290 ppm. An
eight-fold increase is likely to occur in the next two hundred
years if CO^ absorption by oceans is disturbed by ecological
imbalance emanated from man's misuse of the global resources.
The annual concentration of CO^ released from Kasimpur Thermal
Power Station, near Aligarh, U.P. (India) has been noted to
range from 1.804-2.664 per hour (Amani, 1982b).
Plant growth is the cumulation of a series of biochemical
and physiological processes related to uptake, assimilation,
biosynthesis and translocation. For growth to occur, plants
must assimilate carbon dioxide and convert it into organic sub
stances, an inhibition in carbon assimilcition (photosyntnesis)
may be reflected in plant growth.
Grov;th of plants is influenced by high C0„ concentrdtion
due to alterations in photosynthetic characteristics (Hotstra '-
: 53 :
Hecketh, 1975; Hicklenton ^ Jolliffee, 1978). Growth rate was
enhanced on exposure to high concentration of C0„ in Zea mays
(Whips, 1985), Glycine max (Sionit e^ _al. 1987), some floating
aquatic plants and terrestrial species (Idso et_ al. 1987),
Bouteloua gracilis (HBK) (Riechers ' Strain, 1988).
Effect of COp enrichment depends upon a number of meteoro
logical as well as internal factors of plants. Govindjee (1982)
pointed out that cotton plant grown at high carbon dioxide con
centration exhibited reduction in the assimilation rate and
RuBPc are activity per unit leaf compared to plants grown in the
normal air thus leading to an increase in weight per unit area
of leaf.
Total dry matter of plant was increased in Glycine max
(Peet, 1984), Ochroma laqopus and Pentaclettra machlob (Ober-
bauls, 1985), Lycopersican esculentum. Six cultivars of Lactuca
sativa (Mortensen, 1985), and Bouteloua qraulis (Heichers, 1988).
Root dry weight was increased in Echinochlo crusgalli and
Eluscine indica (Potvin 1984) and Triticum aestivum (Kendale,
1985), but Phaesolus vulgaris showed no significant effect
(Jolliffe, 1985).
Similarly, dry weight of leaves was increased in response
to elevated CO^ concentration in Glycine max CV Bragg. ^Sllonlt,
1983; Vu, Joseph, 1989; Leadley, 1989). Ochroma laqopus and
: 53 :
Hecketh, 1975; Hicklenton A Jolliffee, 1978). Growth rate was
enhanced on exposure to high concentration of C0„ in Zea mays
(Whips, 1985), Glycine max (Sionit et. . 1987), some floating
aquatic plants and terrestrial species (Idso et_ al. 1987),
Bouteloua gracilis (HBK) (Riechers ^ Strain, 1988).
Effect of C0„ enrichment depends upon a number of meteoro
logical as well as internal factors of plants. Govindjee (1982)
pointed out that cotton plant grown at high carbon dioxide con
centration exhibited reduction in the assimilation rate and
RuBPc are activity per unit leaf compared to plants grown in the
normal air thus leading to an increase in weight per unit area
of leaf.
Total dry matter of plant was increased in Glycine max
(Peet, 1984), Ochroma laqopus and Pentaclettra machlob (Ober-
bauls, 1985), Lvcopersican esculentum. Six cultivars of Lactuca
sativa (Mort ensen, 1985), and Bouteloua qraulis (^eichers, 1988).
Root dry weight was increased in Echinochlo crusqalli and
Eluscine indica (Potvin 1984) and Triticum aestivum (Kendale,
1985), but Phaesolus vulgaris showed no significant effect
(Jolliffe, 1985).
Similarly, dry weight of leaves was increased in response
to elevated C0„ concentration in Glycine max CV Bragg. (Silonit,
1983; Vu, Joseph, 1989; Leadley, 1989). Ochroma laqopus and
: 54 :
Pentac le t t ra macnloba (Oberbauer, 1985) and Phaseolus vu lga r i s
( J o l l i f f e , 1985). In Nerium oleander.leaves the fresh weight
increased (Downton jet a l . 1980) when grown at twice the atmos
pheric C0„ concentrat ion. However, the leaf dry weight decreased
in Pisum sativum (Paez, 1980). There was no s ign i f i can t e f fec t
in plant biomass even on increasing CO concentrat ion in Carex
biqelowje, Betula nana and Ledum palustree (Oberbauer, 1980).
Elevated concentration of C0« enhanced the number of branches
(Sionit , 1987) and r a t e of branch internode elongation in
Glycine max (Rogrers, 1984), and increased the t o t a l length of
branches and main stem in Ipomea batatas (Bhattacharya, et^ a l .
1985).
Information on plant injury caused by C0_ enrichment i s
scanty. High CO^ concentration caused ch lo ros i s in leaves of
Paseolus vulgar is (Ehert -^ J o l l i f f e , 1985), marginal necrosis
in Lycopersicon esculentum and Lactuca sa t iva (Mortensen, 1985)
and symptoms of s t ress including mottling mild needle absciss ion
in Pinus penderosa (Houpis et. al. 1988). The leaves show ear ly
senescence in glycine max (Sionit jet al^. 1987) and Pinus
penderosa (Houpis et al.. 1988). At elevated C0„ concentrat ion,
early appearance and enhanced expansion r a t e of leaf were noted
in Glycine max (Rogrers et aJ. 1984; Leadley ^ Reynold, 1989).
Numerous works support the view that CO^ enrichment brings
about var ia t ions in a number of physiological processes such as
: 55 ;
photosynthesis. Govindjee (1982) found that the increased
concentration of atmospheric CO- affects photosynthesis by
reducing (a) the fraction of soluble protein allocated to RuBP
carboxylase/oxygenase and (b) the enzyme concentration per unit
leaf areas, chlorophyll or fresh weight. Law and Mansfeild
(1982) suggest that the additional C0_ may also act at metabolic
levels, for it increases the rate of photosynthesis and there
fore provides cells with increased capacity for repair processes
or detoxification mechanism.
An increase in the amount of CO^ (up to 1%) causes a rapid
increase in photosynthesis (Kochhar, 1982) in Glycine max
(Havelka, 1984; Ackerson, 1984; Huber, 1984) and Triticum
aestivum (Kendall, 1985). However, a decline in photosynthetic
rate in response to elevated carbon dioxide was found in Phaseolus
vulgaris and some deciduous trees (Eherct et. . 1985; Williams
et e^. 1986).
No change was found in net photosynthetic rate in Betula
lana, Carex biqelowie and Ledum plaustree (Oberbauer, 1980),
Diqitaria sanqlialis, Echinochloa crusqalli» Elucine indica and
Staria faberi (Sionit, 1985).
The net assimilation rate was also affected. Carbon
dioxide enrichment increased the net assimilation rate in
Echinochlo crusgalei and Elusime indica (Potvin -- Strain, 1984).
: 56 :
Leaf area increases in Glycine max (Clough -4 Peet, 1981,
Baker et al,. 1989), Phaseolus vulgaris (O'leary £t al. 1981),
Ochroma laqopus and Pentaclettra macnloba (Oberbauer, 1985),
Ipomea batatas (Bhattacharya ejt al. 1985), Pueraria lobata and
Loniara japonica (Sack, 1986) and Boutelona gracilis (Richers,
1988).
Heath (1950) demonstrated that CO^ causes stomatal closure
which limits the gaseous exchange. This may in turn, raise
internal concentration of CO2 considerably and thereby retard
respiration. Various observations indicated that the stomatal
operture was reduced in response to enhanced CO^ concentration
(Meidner -2; Manf eild, 1968; Majernik -g: Mansf eild, 1972; Srivastava
et al. 1975b; Black, 1982), leaf conductance was decreased in
Glycine max (Haneelk et . 1984).
The resperation rate is enhanced in Phaseolus vulgaris
(Ehert ^ Jolliffe. 1985). In Commelina communis, stimulation
of the stomatal opening is enhanced by ATP. But the internal
ATP level, ATP/(ADP and AMP) ratio, and respiration rate are
diminished ^Saish et . 1989).
Plants may also very in respect of quantity of enzymes
for the fixation of CO^, light saturation point, and the ability
to tolerate high CO2 concentrations (.Devlin, 1973;. At high C0„
concentration, activity of sucrose phosphate synthase was
: 57 :
reduced in Glycine max (Huber et. al.. 1984) but KM of Ribulose
biphosphate carboxylase remained unchanged ^Vu, Joseph et_ al«
1989).
On high concentration of CO * starch accumulation and leaf
sucrose concentration were enhanced in Glycine max (Akerson £t.
a l . l984 ; Havelka et cd. 1984; Huber et ^ . 1984; Vu et a l .
1989) and Phaseolus vulgaris (Ehert ^ J o l l i f e , 1985) .
Leaves of Nerium oleander grown at twice the CO^ concen
t r a t i on , gained in soluble protein per unit area (Downton et_
a l . 1980). In cotton plant , assimilation r a t e as well as RuBPa
ase ac t iv i ty per unit leaf area got reduced (Govindjee, 1982),
High concentration of CO caused no a l t e ra t ion in the ni t rogen
content of Triticum aestivum (Havelka et_ ail. 1984) but TNK
harvested per plant was increased in Glycine max (Allen et a l .
1988).
The stomatal aperture i s reduced in response to enhanced
CO concentration (Meidner ^ Mansfeild, 1963; Majernik -^
Mansfeild, 1972; Srivastava, et, ^ . 1975b; Black, 1982) and i t
r e s t r i c t s the fluxes of gaseous pollutants into a plant which
may help in mitigating the effect of pollution but does not
elemenate them (Law >. Mansfeild, 1982).
Reduction of the stomatal aperture was apparent in Vicia
: 58 :
faba (Spence et_ . 1984) and stomata per leaf increased in
Phaseolus vulgaris (O'Leary £t aJ,. 1981) in response to CO^
enrichment. Leaves of Glycine max thickned due to increase
in number of palisade cells (Vu, et al, 1989). High concentra
tion of CO^ decreases main stream plastochron interval in
Glycine max (Barker et al. 1989).
Yield is affected by high concentration of carbon dioxide.
Increase in photosynthesis, leads to an increased yield (Kreusier
1885; Brown J Escombe, 1902? Pantanelli, 1903). An increase in
yield was reported in Glycine max (Ackerson et^ al_. 1984; Rogers
et. . 1984; Sionit et. al.. 1987; Baker £t .al. 1989) and Triticum
aestivum (Havelka .et .al. 1984; Kendall et al. 1985). Number of
pod and seeds were also increased (Rogers et al. 1984; Ackerson
et .al. 1984), Sionit et, . i* 1987; Baker, 1989).
In Triticum aestivum there was a gain in heads per meter
(Havelka .et .al. 1984) and in dry weight and grain number per
spikelet (Kendall al. 1985), but the harvest index remained
unchanged (Havelka et. al. 1984).
In Ipomea batatas (Bhattacharya et. .^1. 1985), high concen
tration of CO^ made for a greater number and diameter of tubers.
It caused early deveopment of inflorescence in Echinochlo
crusqalu and Eleusine indica (Potvin^ Strain, 1984) and a
decreased protein percentage in seeds of Glycine max (Rogers
et al. 1984).
SULPHUR DIOXIDE
Sulphur dioxide is the second most abundant coutaminant
next only to CO; it accounts for 2Cf^ (by weight) of all pollu
tants. The growing industrialization is responsible for the
rising concentration of SO^. Thermal power plants, crude oil
refineries and automobiles are the major contributors of SO2
accounting for nearly b% of its man made sources. Various
fuels differ appreciably in their sulphur content. Upon combu
stion of a fuel, almost all the sulphur contained in it
transforms into gases (SO^ and SO^ oxides).
S0„ and other oxides of sulphur are produced on complete
burning of fossil fuels in the air. SO is greadually oxidised
to S0« which in turn reacts with the atmospheric moisture and
forms sulphuric acid. The rate of oxidation can be affected by
sunlight and by finest dust particles acting as oxidation cata
lyst.
SO^ is considered as a major cause of pollution injury
to vegetation falling down as SO., both in wet fall (precipi
tate) and dry fall from the atmosphere (Husser e^ _al« 1978).
This has been the subject of numerous surveys (see Thomas, 1951,
1956; Thomas - Hendricks, 1956; Dassler, 1963; Knabe, 1966;
Brandt - Heck, 1968; Daines, 1968; Mudd, 1975; Linzon, 1978).
: 60 :
Different plant species, varietes and even clones vary in
their susceptibility to SO^ (Thomas et al. 1950; Pelz, 1956;
Brandt J?; Heck, 1968; Dochinger ^ Seliskar, 1970; Bigg ^avis,
1980). For example, Caianus caian (Pigeon pea) is highly
sensitive to S0„ pollution (Shew _et al. 1982), while Amaranthus
keeps its growth comparable to that of control plant (Yunus et.
al. 1981).
Changes caused in the plants and physico-chemical proper
ties of the soil by sulphur dioxide can be attributed mainly
to the acidity caused by it. Sulphur dioxide fall out may
affect the plant system directly through the leaf surface or
indirectly through acidity and mineral imbalance of the soil.
Vegetables are most sensitive to S0„ gas in the atmosphere,
Coniferous trees are highly sensitive to SO^. Many conifers
such as Douglas fir (Pseudotsuqa menziesi) and lodogepole pine
(Pinus contorta) are sensitive trees and have died In SO^
pollution region in America. The species which have survived
SO^ pollution include Leonotis and Vitex in North India and
Polygonum cilinode and Sambucus pubens in Canada.
Enough information concerning effect of sulphur dioxide
has accumulated on symptomatology (see Jacobson - Hill, 1970;
Van Haut ^ Stratman, 1970; Malhotra -^ Blanel, 1980; Yu ^ Wang,
1981) and growth responses (Naegele, 1973; Ziegle, 1973a,b,
: 61 :
1975; Dugger, 1974; Mudd-6 Kozlowski, 1975; Mansfield, 1976;
Hallgren, 1987; Koziol 4: Whatley, 1984; Malhotxa-€. Khan, 1984;
Singh _et alj. 1987). Growth i s especial ly suppressed in a lp ine
f i r , Douglas f i r and lodogepole pine (Hedgecock, 1955; Karen -^
Tyden, 1958), scot pine (Grased et ^ . 1981), Clone NE-388
(Populus maximomizii X P. t r ichocarpa Torr X Gray) (Bigg-^ Davis,
1982), Betula papyrifers . B. nigra (Norby, 1983), Phaseolus
vulgar is (Temple et a l . 1985), Medicago sa t iva (Singh et al»
1985), Lollium perenne (Koziol et a l . 1986), Raphanus sa t ivus
(Thomas et, a l . 1987) and Vigna mungo (Lalman, 1988). Sulphur
dioxide reduces growth by affecting ce r ta in physiological p r o
cesses connected with photosynthesis or r e s p i r a t i o n by i nh ib i t i ng
a redisdr ibut ion of assimilates from leaves t o the non-photo-
synthet ic t i s s u e .
I t i s observed that in older plants root growth was more
affected than shoot growth. A reduction in both was observed
in five woody species (Norby J?> Kozlowski, 1981), Melilotus
indica and Solanum nigrum (Ghouse Jl Khan, 1983, 1984), Polygonum
qlabrum and Desmodium triflorum (Khan - Khair, 1984) and Avena
sat iva (Chand et ^ . 1989J. Sulphur dioxide a lso induces redu
ction in height of wheat cu l t ivar N-4 and gram c u l t i v a r H-1450
(Pawar, 1982).
Majority of the recent repor ts suggest t ha t SO may reduce
several components of growth in a range of spec ies ; these
: 62 :
components include snoot dry weight and root shoot ratio
(Taniyama, 1972; Taniyama et al. 1972; Bell>^ Clough, 1973;
Lockyer et ^ . 1976; Ashenden, 1978, 1979; Bell et aj . 1979;
Crittended X Read, 1979; Ayazloo e^ al. 1980; Davies, 1980).
Reduction in root : shoot ratio caused by SO^ is probably
associated with an increase in leaf area ratio (LAR). Bell et
al. (1979) found an increase in leaf area ratio and specific
leaf area with a decrease in root : shoot ratio. Sulphur
dioxide causes decline in root and shoot weights in Medicaqo
sativa (Murray, 1985), fa:«sh weight of green leaves, shoot and
root, root/shoot ratio and dry weight in Lollurn perenne
(Crittenden ^ Read, 1978), Nicotiana tobaccum and Cucumis
sativus (Mejstrik, 1980). Number of roots, leaves and the
fresh weight were reduced in Vicia faba (Agarwal et, al,. 1985)
and Avena sativa (Chand ejt al. 1989). However, exposure to
high concentration resulted in increased dry weight of leaves
in Helianthus annus (Shimizu et_ al. 1980) and Poa pratensis
and other grasses (Whitemore-^ Mansfeild, 1983). Experiments
under two light regimes depicting winter and summer proved that
50^ reduction in shoot dry weight was obvious when SO^ fumi
gation accompanied winter light (Davis, 1980). A high dosage
of SO also reduces root and shoot biomass in Melilotus indica
and Solanum nigrum (Ghouse ^ Khan, 1983, 1984), Polygonum
qlabrum and Desmodium triflorum (Khan-^ Khair, 1984a,b) and
Jackpine (Fealotar ^ a l. 1983; L.'Hirondelle, et. . 1987).
: 63 :
Sulphite ions (SO^) are known to be the most toxic form
of sulphur to plants (Mudd >2r. Kozlowski, 1975). Plants have
an inhernt ability to convert this toxic form to a far less
toxic component, sulphate (SO^). When the rate of conversion
of SO2 to SOg exceeds the rate of conversion of SO- to SO^,
visible injury results. Foliar-injury symptoms are direct
manifestations of phytotoxic nature of SO^ (Jacobson Hill,
1970; Hill et. aJ,. 1974). Leaf injury owing to sulphur dioxide
pollution was reported in Lolium perenne (Cowling, 1978), certain
crops (Khukawa ei, . 1980), Betula papyrif era, and B.. nigra
(Norby-^ Kozlowski, 1983), wheat (Thompson, 1985), Dactylus
qlomerata and Festulus rubra (Wilson Bell, 1986), Qpuntia
basilaris (David et al.. 1987), Betula platyphylla (Tsukahara
et al. 1987), spruce needle (Piene ami Queriroz, 1988) and
Hordeum vulqare (Baker -6. Frillwood, 1986). There exists a
correlation between the foliar injury and the amount of S0_
absorbed (Furukwa et al. 1980). Of the various injury symptoms
recorded for S0„ pollution, tip burn and interveinal necrosis
were the most common. These necrotic lesions hamper growth and
decrease the net assimilation rate of plants (Katz, 1949; Thomas,
1951; Keller, 1958; Weinstein>C McCune, 1970). In case of
necrosis, leaf cells are plasmolysed and finally the tissue is
collapsed (Thomson et. . 1965). The initial plasmolysis causes
changes first in water relations and finally in the structural
: 64 :
integrity throughout the mesophyll (Thomson, 1951). On the
other hand, chlorosis results in loss and retardation of
chlorophyll. The loss of chlorophyll leads to a pale green
or yellow colouration which either partially or completely
overcomes the green colour.
Necrosis may appear as tip burn, banding or basal burn
(Treshow, 1970). It has been reported in Lolium perenne.
Lolium muttiflorus, Dactylis qlomerata and Phelum pratense
(Lockyer, 1985), several fruit trees such as pear, peach ,
grape, apple and chensut (Haselae et_ al. 1986) and grass poplu-
lation (Taylor-4-Bell, 1989). Chronic necrosis was observed
in Arabidopsis thaliana and Mentha piperata (Desanto et_ al»
1979), Arachis hypoqea (Mishra, 1980), Avena sativa (Chand et
al. 1989) and yellow brown necrotic spots in some grasses
(Oin et al. 1981).
The natural weathering of cuticular waxes is enhanced
by SO^. This consequently facilitates pollutant penetration
and also increases rate of the infection by various pathogens
thus intensifying the symptoms simultaneously caused by Mosaic
virus (MOMV) (Laurence _et aj,. 1981). In Phaseolus vulgaris S0„
effectively inhibited disease development (Reynold ^ ^ . 1987),
S0„ enrichment also brincjs about early sensecence
(Stoklasa >-Julius, 1923), In such cases, it appears that
: 65 :
excess expenditure of energy and material to counteract the
biochemical changes induced by SO^ might have accelerated the
ageing of the treated plants (Wellburn et . 1976). It is
also likely that SO^ induced abscisic acid synthesis which
would in turn cause early senescence. High dose of SO^ causes
reduction in nodules in Vicia f aba (Agarwal et aj.. 1985).
The gaseous pollutants enter through stomata of leaves,
and come in contact with the large surface area of most spongy
mesophyll cells which are oxygen rich during the day time. At
this stage, the pollutant may injure cells and eventually get
changed to a less toxic stage. Sulphur dioxide, on entering
the leaves through stomata, dissolves in water contained in the
cell wall and generates bisulphite and sulphite ions as well
as hydrogen ions :
HSO3 ^°3^" + ^^
Thus, the toxic effects of S0„ are likely to be related
to these three kinds of ions. Injury is caused by lowering the
intercellular pH. Sulphur dioxide causes cell injury in bean
(Thomas, 1961) where cells are plasmolysed and protoplast
collapsed (Solberg ' Adam, 19b6). Epidermal cells are the pre
ferential tragets of S0„ (Suwannapinunt A Kozlowski, 1980).
: 66 :
At an elevated level of SO^, plasmolysis takes place in the
spongy and epidermal cells leading to shrinkage and destruc
tion. Intercellular spaces and stomatal periphery increase
(Kim, 1981). The affected tissue becomes desiccated and
flaccid (Treshow, 1970). Cells of palisade tissue shrink and
collapse and the entire leaf reduces in thickness (Katz ^
Ledgham, 1939). Cell membrane also gets altered (Black, 1985).
There are evidences that some pollutants react directly
with leaf cuticle (Godzik A Sassen, 1978; Black J?r Black, 1979;
Cape -?: Fowler, 1981; Huttunen 2. Laine, 1983). The natural
weathering of cuticular waxes has been enhanced by S0» which
may eventually lead to loss of epicuticular wax as in Lolium
perenne (Koziol 4; Cowling, 1981).
Numerous stomata present on the epidermal surface of green
parts of plants, generally leaves, form the principal entry
path for the pollutants. The frequency of stomata varies from
species to species, as well as due to pollution in several
plants such as Psidium quajava (Ghouse >?i Khan, 1978), Croton
bonplandianum (Zaidi et _al. 1979), Ricinus coirununis (Yunus et
al. 1979), Callistemon citrinus (Ghouse ejt a_i, 1980) Calotropis
procera (Yunus ^ Ahmaa, 1981) and Ipomea fistulosa (Yunus et. al.
1982).
Stomata are the principal avenue of SO^ gas in leaves
: 67 :
(Majernik X Mansf eild, 1970; Bisoe et aj . 1973; Bonte et aJ.
1977; Black . Black, 1979; Black X Unsworth, 1979a,b; Mansfield
X: Freer-Smith, 1981; Black, 1982). In the presence of SO2,
stomata stop their closing mechanism; in some case they remain
open even during night (Borka ^ Sardi, 1981) and allow the gas
to enter the leaves.
As sulphur dioxide enters the substomatal cavity, subsidi
ary cells loose turgor while guard cells retain it. It is
followed by changes in membrane permeability CPuckett ^ al.
1977) that may account for an increase in the stomatal aperture
and in transpiration (Squired Mansfeild, 1972; Biscoe et al.
1973). Widening of the stomatal aperture facilitates the entry
of S0„ through stomata, thereby causing more injury to plant in
the form of chlorosis. The literature indicates that stomata
may be induced either to open or close in response to S0„ depend
ing upon the species examined. SO^ enhances the stomatal
opening in Vicia faba (Mansfeild>^ Majernik, 1970), Pine (Farrar
et_ _al. 1977), Phaseolus vulgaris (Ashenden, 1978; Rist-^ Davis,
1979), pea and corn (Ktein _et _al. 1978), navybeans, cucumber,
soybean and white bean (Beckerson A Hofstra, 1979), grapevine
(Shertz et_ . 1980), radish, sunflower and tobacco (Black ^
Unsworth, 1980) and Atriplex triangularis and A. sabulosa (Winner
>' Mooney, 1980). In contrast, stomatal closure or depressed
: 68 :
transpiration was reported in pine (Caput et . 1978), peanut,
tomato, rice and spinach (Kondo - Sugahara, 1978), Diplacus
aurantiacus and Heteromeles arbutifolia (Winner ^ Mooney, 1980a,
b), Coastor oil, Swiss chard, rice, poplar, plane, sunflower,
cucumber (Furukawa ^ . 1980), wheat, corn, sorghum and bean
(Kondo £t ^ . 1980), apple (Shertz et . 1980) and birch (Bigg
^ Davis, 1980), The closure in stomata was due to a loss of
turgor cells (Mansfeild >4 Freer-Smith, 1984).
The pollutant-induced changes in stomatal aperture have
important consequences. Firstly, there will be either enhance
ment or depression in photosynthesis, transpiration water loss
and C0„ uptake. Secondaly, the rate at which the pollutant
enters the plants and arrives at the metabolic site will be
altered.
Kondo and Sugahara (1978) and Kondo _et . (1980) observed
a relationship between leaf abscisic-acid level (ABA) and the
stomatal response. Tne species with the largest amount of ABA
had rapid reauction in transpiration on exposure to SO^, whereas
in those with very low level of ABA transpiration rate initially
increased and then slightly decreased. Also, inhibition in
transpiration occurred due to stomata closure (Van Hassett -^
Wassen, 1982). Depression in the rate of transpiration (Lore 4-
Andreas, 1987), was reported in Phleum pratense (Teresa ^
: 69 :
Mansfeild, 1982), Glycine max (Takemoto ^ Noble, 1982),
Fraxinus pensylvinla. Liriodendron tulipifera, and Zea mays
(Taylor, 1985). 'Transpiration coefficient' was altered in
Dactylis qlomerata and Phleum pratense (Lockyer, 1985). In
some cases due to high concentration of S02» the leaf stomata
could not shut during night which leads to excessive transpi
ration (Borka et al. 1981).
Reports on the effect of SO^ on stomatal conductance are
contradictory (Majernik - Mansfeild, 1970; Biscoe ejt aJ,. 1973).
Reduction in stomatal conductance was reported in Phascolus
vulgaris (Temple _et ail, 1985), but it increased in Vicia f aba
(Black A Black, 1979). Koziol and Jordon (1978) proposed that
increase in stomatal conductance reported by Mansfeild and
Majernick (1970) may be the result of enhanced internal CO^ con
centrations caused by SO^ induced enhancements in respiration.
Numerous reports (Mudd, 1975, Hallgren, 1978; Heath, 1980)
indicate that photosynthesis is very sensitive to SO^, and that
S0„ exposure results in depressed net photosynthesis rate
(Stoklasa et_ _al. 1923; Katainen, 1987; Steubing Fangmeier,
1987; Steubing ^ Fangmeier, 1987; Price X Long, 1989; Saxe -^
Murali, 1989) as in Phleum prantense (Teresa Mansfeild, 1982).
Glycine max (Takemoto^ Noble, 1982), Liriodendron tulipif era.
Fraxinus pennsylvinia and Zea mays (Taylor, 1985), Marchantia
polymorpha and M. timctorium (Takaoki et. al. 1986) Hordeum
: 70 :
vulqare, Lolium perenne and Vicla f aba (Darrall, 1986) and
Pisum sativum (Aischer, et al. 1987;.
No single mechanism explaining the action of SO- on
photosynthesis has been identified. The reduction in photo
synthesis will result partly from the inability of cells to
sustain photosynthetic rates during pollution uptake and partly
by the action of any detoxification mechanism which may indire
ctly impair photosynthesis by competing for energy supplies
used in photosynthesis. Similarly, energy may be channelled
into repair mechanims rather than into photosynthesis, growth
and development (Wellburn et . 1976). Thus the magnitudes of
reduction in the photosynthesis are the combined action of SO^
on stomata and a number of respiratory and biochemical proce
sses. Therefore, SO^ on entering the leaves gets metabolized
to sulphite, bisulphite and sulphate (Puckett et. aj,. 1973) which
affect several biochemical processes and cellular characteristics
(Horsmann X Wellburn, 1976) thereby causing inhibition of photo
synthesis.
Some workers reported a temperory enhancement in photo
synthesis (Black ^Unsworth, 1979b, Winner^ Mooney, 1980).
These enhancements can often be attributed to increased stomatal
conductance or perhaps to depressed photorespiration.
Enhancement in 50^ concentration results in retardation of
CO fixation. Ziegler (1972, 1973) reported that inhibition of
: 71 :
photosynthetic CO^ fixation by SO^ was due to competition
between CO^ and sulphur products for active binding sites on
Ribulose biphosphate (RuBP) and Phosphoenol pyruvate (PEP)
carboxylase enzyme. At a high SO^ concentration this inhibition
was non-competitive.
At an elevated concentratipn, SO^ inactivates iron of
chloroplast thus interfering with its catalytic properties,
which eventually breaks down chlorophyll and kills cells (Noack,
1929). Thus, high concentration of SO2 leads to a reduction
of photosynthetic pigment content. The breakdown of chlorophyll
may be attributed to S0„ which induced removal of Mg ions by
two atoms of hydrogen from chlorophyll molecules which converts
chlorophyll into pheophytin (Rao - Le Blanc, 1966; Malhotra,
1977). Chlorophyll content gets reduced in Triticum aestivum
(Pandey -^Rao, 1978), Mentha piperata and Arabidopsis thaliana
i>~>e Santo et aj,. 1979), lady's finger (Borka et al. 1981;
Shingri, 1982; Agarwal et al,. 1987), Glycine max (Prasad - Rao,
1982), Phaseolus vulgaris ev. Processer (Saxe, 1983), Triqolum
subterraneum (Murray, 1985), Solanum tuberosum (Kumar _et al.
1986) and Raphanus sativa (Tomar et. ad. 1987) under the impact
of SO^.
Chlorophyll a is more sensitive to S0„ than chlorophyll b
(Lauenroth > Dodd, 1981). A reduction inLCarotenoid pigements
was also observed due to S0„ fumigdtion (Agarwal .et. aJ. 1987)
: 72 :
in western wheat (Laurenroth '2:'Dodd, 1981), Oryza sativa
(Nandi et, al. 1986) and Syzyqium cumini (Vijayan Bedi, 1988).
Caxotenoid and chlorophyll contents were both reduced in Oryza
sativa (Agarwal et. . 1982), Maqnifera Indica and Prosopis
iulifora (Pawar, 1982; Pawar >4 Dubey 1981). According to
Beckerson and Hofstra (1979), increased SO^ concentration may
cause an increase in chlorophyll a and b.
Enhanced SO^ reduces protein content. This might be the
result of a decreased photosynthesis (Sij -€; Swanson, 1974),
inhibition of protein synthesis, or enhanced protein degrada
tion (Robe-!?:-Kreeb, 1980). Cecil and Wake (1962) pointed out
that disulphide bonds in cystine are readily broken by sulphite
(SOo ). A reaction of sulphite with disulphite bond existing
in protein would result in the disruption of tertiary structure
of protein and hence leading to its degradation. Protein content
was reduced in white bean (Beckerson > Hofstra, 1979), Glycine
max and Pisum sativum (Sardi, 1981), wheat cultivar N-4 and gram
Cv H-1450 (Pawar, 1982), Candendula officinalis (Singh et. aj,.
1985), Triqolum subterraneum cult woogenelhep and Lolium perenne
cult Tetralite (Murray, 1985) and Syzyqium cumini (Vijayan A Bedi,
1988).
SO^ lowers carbohydrate level in Phaseolus vulgaris (Koziol
-^ Jordon, 1979) and Syzyqium cumini (Vijayan -C Bedi, 1988) and
increases it in Triticum aestivum cultivar RR21 (Prasad J-, Rao,
: 73 :
1981). The level of soluble sugars increased in Hordeum vulqare
(Farooq et al,. 1982j. Starch level was reduced in Phaseolus
vulcfaris i.Koziol J2:rJordon, 1979; Saxe, 1983), Oryza sativa
(Nandi et al. 1986) and Pinus ponderosa var scopulorum (Karen-
lampi et al,. 1986).
As the concentration of S0„ or its flux into the plant
increases, SO^ may influence a greater number of characteristics.
Concentration of ascorbic acid decreases at increased SO^ con
centration in Glycine max (Prasad 4: Rao, 1982) Syzyquium cumini
(Vijayan -^Bedi, 1988) and Viqna radiata (Singh -grRao, 1988).
Exposure to S0„ lowered the amount of free fatty acid
followed by polar lipids in soybean (Grunwald, 1981). Glyco-
lipids got reduced in pine needles (Khan 4rMalhotra, 1977).
The contents of mytric acid, oleic acid, linolic acid and lino-
lenic acid of lipid in wheat leaves declined 6n exposure to
SO^/HSO^~; (Cai, 1985).
On entering the leaves, SO^ dissolves in water present in
cell wall and generates bisulphite (HSO^), sulfite (S0_ ) and
hydrogen ions (H ). The presence of these ions lowers pH,
making it acidic and simultaneously injurious, A reduction in
leaf extract pH was reported in Mentha piperata and Arabidopsis
thaliana (De Santo et al. 1979), Glycine max (Prasad ^ Rao,
1982) and Cadendula officinalis (Singh et . 1985). Wu (1982)
: 74 :
stated that the susceptibility of plants to S0„ was related to
pH of their sap. Plants with lower pH values were more suscep
tible, while those with pH values around 7 were resistant. The
effect of pH of SO^ injury comprises {!) the direct destructive
action of acidity and (2) the indirect effect due to the influ
ence of pH on the partition among the three species existing in
- 2— the solution, HSO^ , SOo and undissociated H^SO^ molecules.
Enhanced concentration of SO^ interfered with nutrient
uptake in Vicia faba (Agarwal et^ al,. 1985). Significant
increment in foliar sulphur concentration on exposure to S0„
has been assessed in leaves (Heggested et al.. 1986) of Lolium
perenne (Cowling, 1978), Arachis hypoqea (Mishra, 1980), wheat
(Milchunas et. . 1981; Bytenerowicz et al,. 1987), and Glycine
max (Prasad -^Rao, 1982). Sulphur content of shoots was low at
low concentration of S0„ in Medicaqo sativa (Lockyer and Cawling
1981). The sulphur gets incorporated into chloroplast lamella
during S0„ fumigation (Ziegler, 1977) and is thought to affect
tfieir membrane. Nitrogen and phosphorus concentrations decrease
at a high SO^ concentration in Arachis hypoqea (Mishra, 1980),
The phytomass (g/dry wt/plant) and ultimate product of metabolic
activities, was increased until maturity, but decreased during
the senescence. The phytomass value was low with an increase in
the pollutant dose. Thus, phytomass accumulation and the net
: 75 :
primary productivity decreased in Arachis hypoqea (Mishra, 1980),
Triticum aestivum cult RR21 (Prasad -^Rao, 1981) and Vicia f aba
(Agarwal et aJL. 1985) alongwith reduction in the net assimilation
rate in Populus tremuloides and Pinus banksiana seedlings
(L'Hirondelles et al. 1987).
Sulphur ions inhibited ATP formation in mitrochondria
(Ballantyne, 1973); thus SO^ depressed ATP level (Harvey Z
Legge, 1979) and had a deletrious effect on ATP utilization
(Yoneyama, 1979). S0„ interferes with the regulatory process
(Marewa Ji'Schoepe, 1976) and light activation of Calvin cycle
enzymes (Schmidt, al . 1988). Several enzymes involved in
amino acid metabolism are affected by SO^ (Malhotra J?rSarkar,
1979; Heath, 1984). To sum up, the action of S0„ on enzyme may
involve a direct disruption of enzyme structure or a direct
effect on a catalytic site or an indirect effect on cofactor.
Light activation of fructose-1,6-biphosphate was sensitive to
S0„ (Alscher^Herman, 1982). SO^ inhibited photoconvertibility
of the soluble chlorophyll protein (Sugahara _e;t . 1980). NAD
and NADP dependent malate dehydrogenase activity got inhibited
by SO^^" (Ziegler, 1974) or by SO2 (Sarkar -*>Malhotra, 1979).
SO^ increased reactive substances mainly malondialdehyde (MDA)
(Shimazaki e_t a_l. 1980) and peroxidase activity (Li ^ . 1981)
in Oryza sativa (Nandi et, . 1986), while catalase activity
: 76 :
(Nikolaevskiy, 1966). SO^ increased citric acid cycle (Kreb
cycle) in Betula but decreased it in Acer (Nikolaevskiy, 1968).
SO^ also interfered with carbon metabolism and transport in
soybean (Griffith J^ Campbell, 1987^ and damaged photosystem II
(Schmidt et eil. 1988).
Long term fumigation with SO^ has ?hown vacuoles with
darkly stained deposits, lipid like large droplets and rounded
chloroplast in the cells of Pinus ponderosa var scopulorum
(Karenlampi 'fisHonpis, 1986).
Chloroplast becomes plasmolysed or bleached on exposure
to SO2 (Unring, 1978; Barton aj,. 1980) or swelled up in the
guard cells of stomata (Black -<i2-Black, 1979a). Ultrastructure
of chloroplast also got influenced in Zea mays (Nyomaekay e_t al.
1986) and spinach leaf (Hiroshi Bt al,. 1989). Mitochondrial
changes were also reported in pine needles treated with SO^
(Malhotra, 1976). SO^ affected the development of thylakoids
in Zea mays (Nojomwekay et. aj,. 1986) and caused swelling in
thylakoid (Black, 1982) and stroma in spinach (Hiroshi e_t .aJ,.
1989). Also, an irreversible damage to thylakoid membranes was
observed (Majernik Wellburn, 1972). These ultrastructural
changes were associated with a depression in the Hill reaction
activity in chloroplasts (Malhotra, 1976). SO^ disintigrated
membrane (Malhotra, 1976j Suwannapinut J- Kozlowski, 1980 ) and
: 77 :
affected the development of the whole of the inner membrane
system in Zea mays (Nojomwekay et. al.. 1986). The initial
effect on cell membrane involves the change of electrial resis
tance (Yand _et ad, 1982). Sulphite caused a cleavage of disul-
phide linkage which lead to membrane disruption (Puckett et_ al.
1974).
Sulphur dioxide causes a break down in the chromosomes of
the vegetative and reproductive nuclei in Tradescantia paludosa
(Ma ^ . 1973), and induces abnormalities in different mitotic
stages in the pollen mother cells (PMCs), pollen grains (PGs)
and tetrads of Vicia faba. The irregularities observed in PMCs
are stickness, lagging and disturbance of chromosome, sticky
bridges, fragment bridges, with fragments and multipolar anaphase
and telophase. PMCs with more than one type of abnormalities are
frequently observed (Amer £t al. 1989),
Due to SO^ fumigation RNA level gets affected in white bean
(Backerson, 1979).
At an elevated concentration of SO leaf conductance and
xylem tension decreased (L'Hirandelle Addison, 1987), along-
with a decrease in the lateral water flow into the sieve tube
brought about by a recuded phloem loading along the length of
a leaf and reduced speed of translocation in Triticum aestivum
and Zea mays (Gould et al. 1988). - • ^ ^^"^-^v ~
^34 V- D-S %
: 78 :
S SO^ reduced the width of annual rings in Pinus nigra
(Gilbert, 1983} and retarded the annual increment of wood in
certain trees such as Dalberqia sissoo and Tectona qrandis
(Khan 1982; Ghouse et . 1984a, b).
Effects of S0„ on reproductive plants organs are little
explored. An increase in air pollution is correlated with yield
decrease (Warteresie-^ Wicz, 1979). Most of the recent reports
suggest that SO^ may reduce several components of yield (Ashenden.
1978, 1979; Bell et aJ. 1979; Crittenden Read, 1979; Ayazloo,
et. al. 1980; Davies, 1980), in Glycine max (Sprungel et. .
1981), several species of American grassland (Lauenroth et al.
1983), rice (Kats e^ ^ . 1984), wheat, rye, barley, pea and
grapevine (Catanesw ejt al.. 1987), Viqna munqo (Lalman c Singh,
1988) and Phaseolus vulgaris (Keynolds et. aj,. 1989). Van Haut
(1961) found that yield loss depended on the growth stage of
the plant at the time of pollutant exposure.
A reduction in production level of plants (Lore -C- Andreas,
1987; Singh et, j^. 1989) and primary productivity and fruit
number in Triticum aestivum cult RR21 (Heggested et_ al. 1986),
Vicia faba (Agarwal jet .al. 1985), resulted from retardation in
the photosynthetic rate followed by a decreased photosynthetic
area due to leaf injury, reduced pigment content and leaf extract
pH.
: 79 :
SO^ effect fruit weight in pigeon pea C^hew et . 1982).
Seedlings were also sensitive to SO^ fumigation in Betula
ple tvphylla (Tsukahara et^ al.» 1987). Number of seeds got
reduced in Pinus svlvestris (Rouges _et aj., 1980) and Glycine
max (Sprungel, £t. . 1981), in which mean weight per seed and
harvest ratio also got reduced. Analysis of thousand grain
(seed) weight (TGW, TSW) compared with total grain (seed)
suggests that the number of grains (or seeds) per unit ground
area was more affected than their weight.
SO^ decreased seed germination rate in Dalberqia sissoo
(Khan, 1982) and red pine (Ridding Ar Boyer, 1983) and spores
germination in Adiantum capillusvenesis (Wada et^ ai.. 1987),
but the germination percentage increased in Zea mays (Chand -^
Yadav, 1989).
Flower production was retarded on exposure to SO^ in
Acacia arabica and Delonix reqia (Pawar, 1982), and Maqnifera
indica (Pawat ^ Dubey, 1983) while flower and pod maturation
was advanced in Viqna munqo (Lalman -^ Singh, 1988).
The cones of Pinus svlvestris showed an increased rate of
abortion, a delayed lignification and reduced dimensions and
weight. (Rogues, et aJL. 1980). Studies on eastern white and
red pine demonstrated that reproductive organs of pines were
: 80 :
affected at concentration lower than those which generally-
caused apparent leaf damage (Hauston > Dochinger, 1977).
SOrt also affected fruit formation in Dalberqia sissoo and
Tectona qrandis (Ghouse - Amani, 1978) and caused fruit
disease in Cassia fistula (Ghouse et. al, 1979).
It affected pollen grains by inhibiting pollen germination
and tube growth in Cicer arietlnum. Nasturtium crudicum.
Petunia alba and Tradescantia axillaris (Varshney^ Varshney,
1981). A significant percentage of non-viable pollen grains
was observed, on exposure to SO^, in Vicia f aba (Amer et_ al»
1989).
NOx
Nitric oxides (NO), nitrogen dioxide (N0„) and nitrogen
tetroxide (N^O.) are significant air pollutants. Any combus
tion process which produces high temperatures in the presence
of nitrogen and oxygen will yield nitrogen oxides (NOx). Coal
burning alone accounts for 80% of NOx in the atmosphere (Morri
son, 1980). Transportation contributes 30% of NOx emission in
U.K. and West Germany, 40% in Japan and 45% in U.S.A. The
annual emission of NOx in North America and West Germany is
30x10^ tonnes.
Nitrogen oxides are formed mainly by burning of fossil
fuels. Nitric oxide, for example, forms in the heat of combus
tion when the atmospheric nitrogen and oxygen combine.
N2 + 0^ ^^^^ > 2N0
There is then a spontaneous but not necessarily rapid
reaction between nitric oxide and oxygen
2N0 + ©2 > 2NO2
The conversion of NO to NO^ can be accelerated in the
presence of 0^ (Eggleton, 1974).
: 82 :
NO and N0„ are toxic directly in their gaseous form and
indirectly in the form of acid precipitate. The nitrate
compounds resulting from NO emission are believea to account
for more than 40% of acid precipitate in USA and Canada and
35% in West Europe (Chadwick, 1983).
NO^ absorbs visible light and generates highly reactive
oxygen free radicals. These radicals start chain reaction
giving rise to the secondary pollutants such as peroxyacetyl-
nitrate (PAN) and HNO^. It is the presence of these free
radicals and atmospheric acidity that governs the extent of
formation and build up of the secondary pollutants and oxidation
of NO2 (Fuhrer, 1985). Studies with N""" labelled NO2 have
15 confirmed that NO2 may be converted into nitrate and nitrite
(Yoneyama -^Sasakawa, 1979).
NOx causes great damage to vegetation (see Wellburn, £t
M * 198).
NO and NO^ in combination have synergistic effects. The
total pollutant uptake is higher for NO2 than for NO. While
the small fraction of NO was more effective in suppressing
various activities of plants. NO is sparingly soluble in water
(intercellular water present in cell wall), whereas NO- is
highly soluble. Depending upon the difference in solubility NO
: 83 :
and NO^ are taken up by plants possibly at different rates.
The uptake of NO^ by sweet pepper leaves is three times that
of NO when both are present at equal concentration (Law -^
Mansfeild, 1982).
The effect of NO^ varies between species and with time
of exposure period and its uptake is correlated with its con
centration in the atmosphere, as has been demonstrated in bean
(Rogers et_ a^* 1979) and potatoes (Sinn et_ al. 1984).
Oxides of nitrogen alone are unlikely to inhibit plant
growth except when present at very high concentration or on
chronic exposure. Depending upon the time of exposure and the
dose (concentration X duration of exposure) plant growth is
promoted, inhibited or affected by NOx.
Reduction of various physiological processes would lead
to retardation in growth. Wellburn _et . (1981) have shown
that NOx fumigation results in changes of several enzymes level
within the cell. These changes inevitably utilize energy and
materials which would have been available for growth.
The reduction growth during winter was attributed to the
greater sensitivity of the polluted plants to cold stress;
while recovery during the following summer was attributed to
foliar uptake of NO^ and a consequent higher relative growth
: 84 :
rate (Mansfeild et . 1985). Similarly, the level of NOx
increases at night while during day it decreases due to the
partipation of nitrogen oxides in photochemical reaction.
Severe pollution effect was found to be associated with retar
dation of growth in tomato plant (Anderson -t Mansf eild, 1979;
Mansfeild, 1982), wheat (Prasad & Rao, 1980) and certain grasses
(Whitemore -^Mansfeild, 1983), and cause severe damage to stem
and root of maize and soybean (Okano - Totsuka, 1985). How
ever, NOx caused no effect on various parameters studied in
tomato plant (cv. Fireball) (Marie Ormrod, 1984).
There are several reports of N0„ fumigation promoting
plant responses. For example, it increased leaf area and dry
weight in cucumber, kidney bean and sunflower (Yoneyama ejt al.
1980) leaf number in Dactylis qlomerata (Ashenden, 1979b) leaf
area ration in maize and sunflower (Okano - Totsuka, 1985) dry
weight of Tilla cordata and Betula pendula (Whitmore - Freer-
Smith, 1982), dry weight of root in Lolium multiflorum
(Ashenden Williams, 1980) and dry weight of shoot in Pea
(Whitmore -€ Freer-Smith, 1982; Lane -€. Bell, 1984). Neverthe
less, in some cases NOx treatment caused reduction in dry
weight (Whitemore e_t aj,. 1982) eg. in pepper plant (Law ^Mans
feild, 1982), potato (Sinn ejt aj,. 1984), maize and sunflower
(Okano -2, Totsuka, 1985), tomato (Anderson -^ Mansfeild, 1979)
and Poa pratensls. Pheleum pratense and Lolium multiflorum
: 85 :
remained unaffected (Ashenden A Mansfield, 1978; Ashenden
Williams, 1980).
The promotive effects associated with enhancements in
various morphological features are attributed to gaseous NO
end NO^ functioning as aexla.! fertilizers under conditions of
nutrient deficiency (Anderson J2: MansfeiId 1979; Singh, 1980;
Whitmore Freer-Smith, 1982).
NOx damages leaves of various plants such as sunflower
and maize (Okano ^ Totsuka, 1985) causing cell damage due to
acidification. Leaves developed abscission in potato (Sinn
et. al. 1984) and necrotic lesions and scroching in Diffen-
bachia maculata (Saxe - Christensen, 1985). Two kinds of injury-
characterized by leaf necrosis include 'Chronic injury* occurring
due to long term exposure to low concentration of pollutant,
and 'acute injury* as r'eveloped in potato leaves (Khikawa et. a.l.
1982), resulting from short term exposure to high NOx concen
tration.
While chronic injury is not as common as acute injury,
a few plants show an enhanced green colour which later leads
to chlorosis and abscission of the leaves (Ashended -^ Williams,
1980; Elkiey > Ormrod, 1980; Reinerts £-Saunders 1982; Whit
more-^ Freer-Smith, 1982). Injury manifests itself only when
plants are unable to detoxify the absorbed NOx by reduction to
organic compounds.
: 86 :
-fe Zeevaart (1972) distinguished that the necrotic lesions
which correlated will with nitrite accumulation in the leaves
and are believed to be the result of acidification. NO in
water produces a mixture of nitrous and nitric acids :
2 NO2 + H^O > HNO3 + HNO2
In light, nitrite is rapidly converted to ammonia thereby
consuming large amounts of acidity :
N02~ + 3NADPH + BH" — > NH "*" + 3NADP^ + 2H2O
Lack of reducing power in darkness leads to nitrite
accumulation, acidification and necrosis even at low N0„ con
centration.
Leaf injury occurs when a certain threshold pH is reached,
leading to an altered calcium balance of the cell (Heath, 1980)
Young leaves are more resistant than older leaves.
NOx promoted shoot growth of trees like Tilia cordata,
Betula pendula and Alnus incana during the first year of expo
sure, but these beneficial effects were lost during the second
year of exposure (Freer-Smith, 1984).
NOx make their way through the stomata into the leaf
(Bull - Mansfeild, 1974), thus stomatal conductance is impor
tant (Kaji ejl « 1980). But absorption in some ornamental
87
plants was found to be unrelated to the stomatal opening
(Saxe, 1986b). There are differences in boundary layer and
stomatal resistance at local sites on the same leaf, and also
in the stomatal uptake of NO^ at these various sites (Omasa
et al. 1984). Also, the rate of uptake of a gaseous pollutant
is dependent on several physical factors such as stomatal resis
tance (Bennett et^ ^ . 1973). Importance of diffusive resis
tance of stomata for uptake has been emphasized by several
workers (Rogers ejt . 1979; Rogers et. al. 1979; Fuhrer -^
Erismann, 1980; Elkiey A Ormrod, 1981; Sinn et. . 1984).
NOx reduced transpiration rate in bean, this was attri
buted to partial closure of stomata (Srivastava et. aj.. 1975).
Transpiration rate declined in Norway spruce (Kammerbauer et.
al. 1987) and Picea abies (Saxe .et al,. 1989) while in sun
flower, the transpiration rate remained unaltered (Furukawa
et. al. 1984). Fumigation of NOx reduced stomatal conductance,
dark respiration and photorespiration in soybean (Carlson, 1983),
in some cases, on the other hand, increased stomatal conductance
(Ashenden, 1979) and root respiration (Ito .e_t .al.. 1985).
However, NOx affected the transpiration much less than
photosynthesis (Furukawa ^L . 1984). Reduction occurs in the
rate of photosynthesis in certain grases (Whitermore-^ Mansfield,
1978), sunflower (Furukawa et_ aJ,. 1984) and soybean (Sabaratnam
88 :
et aJ,. 1988). Wellburn e.t ad. (1972) showed that fumigation
with N0„ causes a reversible swelling of thylakoids in the
chloroplast of Vicia faba. A physical disruption like this is
responsible for the reducea photosynthetic rate. Electron
transport inhibition, thylakoid membrane damage leading to
leaky membranes resulting in a reduced H"*" gradient, and conse
quently less ATP formation and enzymatic inhibition appear to
be some of the mechanisms involved in suppression of photo
synthesis by NO2.
Fumigation of NOx results in a decrease of chlorophyll
content (Sabartram et. aj^. 1988) in various plants such as
Triticum aestivum (Prasad et. a_l. 1979), albeit an increase in
chlorophyll content is also reported some case such as Dactylis
qlomerata (Singh, 1980; Elkiey-^. Ormrod, 1980). This increase
is thought to be due either to a general promotion of chloro
plast biogenesis (Srivastava -^Ormrod, 1984) or to a nitrogen
nutrient stimulating production of chlorophyll (Singh £t al.
1980).
It is established that NOx are absorbed an assimilated in
plants (Durmishidze Nutsubidge, 1976; Rogers e_t al. 1979;
Yoneyama et al, 1980) through nitrate , 5.Nitrite — ^ammonia
?. amino acid (Kaji et. a^. 1980i. Wellburn et. aj,. 1981; Ito
e^ a^* 1984), and transported to other parts of the plant
(Rogers £t i^. 1979; Okano e.t. . 1984). After fumigation with
: 89 :
N0„, pea plant showed a higher content of nitrate and nitrile
ions. With an associated increase in the rate of protein syn
thesis (Zeevart, 1976). There is an increase in protein synthe
sis through NO^ reducing ammonium, followed by the formation of
amino acid and finally of proteins. Thus, an enhancement in
protein content was obvious in wheat (Prasad^ Rao, 1980).
When NO and NO^ get dissolved in the extracellular water,
they form nitrate and nitrite ions as reported in spinach
(Yoneyama - Sasakwa, 1979), The absorbed NO^ is assimilated
mostly as amino acids with about 1 per cent remaining as
nitrate and nitrite (Kaji £t. aj.« 1980). This reduction to amino
acid through intermediate nitrate, nitrite and ammonia takes
place via the GS/GOGAT pathway, as the enzyme involved in this
pathway shows an enhanced activity following NOx fumigation
(Zeevart 1974, 1976; Kaji et aj,. 1980; Wellburn _et aj,. 1980;
1981; Srivastava-^ Ormrod, 1984).
Reduction in nitrate reductase activity (NRA) on fumigation
with NOx was reported in Hordecum vulqare (Rowland et_ e l. 1989)
and spruce seedling ^Tischner et. . 1989), and an increase in
nitrite reductase (NIR) appeared in tomato (Aldrige, 1980;
Wellburn et^ al.. 1980). In another cultivar of tomato, nitrate
reductase activity remained unchanged while nitrite reductase
activity increased ^Murray^ Wellburn, 1985). Besides, glutenic
: 90 :
synthetase activity remained unchanged (Tischner _et aj,. 1989).
However, there was an enhancement in GDH, GPT and GDT activity
in tomato CV • Ailsa Cruig (Wellburn et aj,. 1980) and GDH/GS
ratio in Lolium perenne (Wellburn et. . 1981). Increasement in
GDH activity was considered as a symptom of biochemical stress
or a mechanism to help assimilate excess ammonia.
Nitrogen content is also increased on exposure to Noxin
wheat (Prasad-^ Rao, 1980), potato (Sinn et. . 1984), Phaseolus
vulgaris (ito .et jal. 1985), Soybean (Sabaratnam et. aj . 1988)
and spruce seedling (Tischner .et al. 1989).
At sub-threshold concentration, NO^ alone promotes cyclic
electron flow and makes available, through additional photophos-
phorylation, extra ATP (Wellburn et_ ^ . 1981) and also increases
the activity of enzymes involved in N assimilation (Wellburn ejt
al. 1980; Srivastava - Ormord, 1984). Such assimilation, besides
nourishing the plant, detoxifies NOx and their products. ATP
formation and higher energy charge ratio were increased while,
PSI and PSII activity remained unaffected in Lolium perenne
(Wellburn et_ . 1981). Naturally occurring reducing agents
like ascorbic acid, pyridine nucleotide, ferrous ions etc.
readily reduce nitrite to NO, which form complexes with iron,
and these iron-NO free radical complexes are potent inhibitors
of enzymes with -SH group. Complexes are also formed with AMP,
: 91 :
ATP, ferredoxin and cytochromes, interfering with electron
transport (Hill-^ Bennett, 1970).
A decrease in productivity on exposure to N0„ was reported
in Dactylis qlomerata and Poa pratensis (Ashenden X Mansfeild,
1978), wheat (Prasad e_t . 1979; Singh, 1980) and a cultivar
of potato (Sinn J Pell, 1984). This decrease in productivity
was found to be related to the reduction in various physiological
features due to exposure to NOx. A decline in crop productivity
has been observed on exposure to NOx in many plants such as
tomato (Mansfield, 1982) and pepper plant cv 'Belramy' (Law
Mansfeild, 1982). It is also reported that air pollution
can affect crop productivity indirectly, if not directly, by
stimulating the growth and reproduction of crop predators (Feir
^ Hale, 1983).
ozo^E
That the ozone is a major phytotoxicant polluting the •
air was recognised in 1958 (Richard ^ aJ.). Ozone is a
widespread and damaging air pollutant in U.S.A., Europe,
Japan and other industrialized areas of the world (Jacobson
1982; Koziol>^. Whatley, 1984; Treshow, 1984).
Automobiles and industries emit tonnes of hydrocarbons
and oxides of nitrogen in the atmosphere. These compounds
are then transformed into ozone and many other products by a
complexes series of reactions initiated by sunlight.
Nitric oxide (NO) is oxidised to nitrogen dioxide (N0„),
utilizing the oxygen in the atmosphere. However, the energy
from sunlight quickly split nitrogen dioxide (N0„) back to
nitric oxide (NO) and atomic oxygen which combines with mole
cular oxygen of the atmosphere to form ozone.
NO2 — ^ — > NO + 0; 0 + O2 ^ > O3
where m = inert molecule and hv = light energy.
The net reaction is -
NO2 + O2 —?^^^—> NO •(- O3
The deletrious effects of ozone on plant growth and agri-
: 93 :
cultural production are well documented (Laurence-^ Weinstein
1981J Jacboson 1982; Heck et al. 1982, 1983; Heggestad
Bennett, 1984).
Conifers were most affected by ozone. Went (1955) pro
posed that ozonides and peroxides exist in the natural blue
smog over coniferous forest. The sensitive species investi
gated among conifers were falk pine (Pinus banksianaJ.
Austrian pine (P. nigra), ponderosa pine (P. ppnderosa^) and
Virginia pine (P. virqiniana); the tolerant species among them
were balsam and white fir, white and blue spruce, red pine and
Douglas fir (Dochinger, 1974). Various hardwood species were
also found to be affected by ozone exposure. The injured
species were alder, quaking, asper, boxelder, catalpa, honey
locust (Lleditsia triacanthos). silver mable (A. saceharinum).
Sycamore and willon (Hill e_t _al. 1970). Legumes tend to be more
sensitive to ozone than grain crop. Excessive concentration of
ozone resulted in decline of white pine in Cumperland Plateau
area of East Tennessee (McLaughlin al.. 1982).
For a large number of agricultural and natural plant
species, ozone acts as an important direct and indirect agent
of mortality and morbidity (Smith, 1981). Differential res
ponses of plants to ozone have been related to differences in
the enviornmental conditions and generic expression.
: 94 :
Ozone induces a diverse range of effect on the plant and
plant community. Ozone impact ranges from reduced plant
growth, changes in crop quality and alteration in susceptibility
to abiotic and biotic stress like reduction in root width and
intensity of mycorrhiza formation in Festuca arundinacea (Ho
Trappa, 1984), extensive defoliation in Phaseolus vulgaris
(Kohut «» Laurence, 1983), Medicaqo sativa (Takemoto, et al.
1988) and accelerated senescense of flag leaves in Triticum
aestivum (Grandjean-^ Fuhrel, 1989). The increased rate of
sugar decomposition by very low and sub lethal ozone level over
an extended period of time straves the tissue and causes the
permature senescence and leaf abscission.
Plant growth in response to; ozone depends upon a number
of factors including plant species, plant age, ozone concen
tration, exposure time and the enviornmental conditions during
exposure time. The effect of ozone on various plant processes,
from ion uptake to photosynthesis, suggests that growth must be
affected; direct studies of growth responses are limited.
High concentrations of ozone suppress growth (Rohut
Amundson, 1986) in plants such as Dactylis qlomerata. Lolium
perenne and Phalaris aquatica (Horsman et ail,. 1980), Trifolium
subterraneum and T. repens (Horsman _et a^. 1982), peanut
(Arachis hvpoqea) (Heagle _et. ad. 1983), Glycine max (Unsworth
ei . 1984; Amundson et ad- 1986; Kohut et. al. 1986; Carol .et.
: 95 :
al. 1988), Vicla f aba (Agarwal et. . 1985), Acer saccharum
and Quercus rubra (Reich, 1986), Raphanus sativus (Carol et.
al, 1988), Phaseolus vulgaris (Amthor, 1988), Medicago sativa
(Cooley J2, Manning, 1988), Gossvpium hirsutum (Oshima et al.
1979), and Trifolium repens and Fistuca arundinaceae (Montes
_ejt a_l. 1982). Exessive ozone exposure depressed root-growth
rate in yellow poplar (Liriodendron tulipifera) (Jensen, 1985)
and leaf growth rate in silver maple (Acer saccharum) (Jensen,
1982, 1983).
The impact of ozone on leaves is much less as compared to
that on the root (Tingey et aJL. 1971; Reinert ^ Gray, 1980;
Warmsley £t . 1980; Reinert J Sanders, 1982) and crown growth
(Tingey j2: Reinert, 1975; Rebbeck jg: Brennan, 1984).
Shoot growth showed no alterations in Fraxinus americana
and F. pennsylvanica (Catherine jet. al. 1987), Seguio giganata
(Temple, 1988) and yellow poplar seedling (Chappelka jet al.
1988), exhibiting tolerance toward ozone. However, great
losses occurred in Liriodendron tulipifera (Keith, 1985) soybean
corn, wheat and cotton on exposure to ozone (Heggested, 1988).
Ozone fumigation caused reduction in number and size of
potato tubers and per cent dry matter (Pell-^ Pearson, 1984).
Reduction in total dry '•• 'ight was found in Gossypium hirsutum
(Oshima et. . 1979), Dactylis qlomerata. Lolium perenne and
: 96 :
Phalarls aquatica (Horsman e_t al.. 1980), Phaseolus vulgaris
cult contender (Hindawi ejt aj.. 1980), Trlfolium subterraneum
(Horsman et, ^ . 1982) ard T. sepens (Horsman et. aJ.. 1982;
Blum et, a_l. 1982), Populus deltoldes and Trichocarpa (Reich
Lassoie, 1985). Stem and leaf dru weights in Fraxinus c-
pennsvlvanica (Jensen, 1982) and root and shoot dry weights
in Ladino clover were also reduced (.Blurn et e^, 1983). Never
theless, there was no effect on root, stem and leaf dry weights
in Capsicum annuum (Bennett ejt aJ. 1919),
The mature lower leaves which act as the main sources of
photosynthates for root growth were most damaged, suggesting a
reason behind the relative decrease in photoassimilate parti
tioning to root dry matter, leading to reduction in dry weight.
The same pattern was noted for older leaves of Phaselous vulgaris
(McLaughlin-^ McConathy, 1983; Okano al. 1984).
In soybean (Glycine max), ozone exposure causes reduction
in plant biomass accumulation (Endress Q: Grunwald, 1985) and
the above ground biomass of pods and seeds (Khout ^- Amudson 1986;
Khout et aj,. 1986).
Ozone stress caused reduction in RGR in Liriodendron
tulipifera (Jensen, 1985) and in RGR and growth rate in silver
maple (Acer saccharum) (Jensen, 1982, 1983). Also, the production
of leaves is retarded in Trifolium repens and Festuca arundina-
: 97 :
ceae (Monies £t ad. 1982), Populus deltoides and Trlchocarpa
(Reich J?:, Las sole, 1985) and Medicaqo sativa (Cooley>^ Manning,
1988). The number and length of needle in Pinus elliotii and
Pinus densa were reduced (Hogsett et. a^. 1986). On the con
trary, the total number of leaves increased in Capsicum annum
(Bennett £t a^, 1979). 0^ stimulated leaf bud growth but
suppressed leaf growth in Phaseolus vulgaris (Engle -ۥ Gabelman,
1967). Even in soybean, radish and some other plants, ozone
stimulated young plants to produce leaves but damaged the deve
loping leaves (Walmsley _et ad. 1980; Endress ii. Greenwald, 1985).
Ozone exerts the phytotoxic effect only when it reaches
in a sufficient amount the sensitive cellular site within the
leaf. The effects of ozone are classified as injury or damage.
Injury incompases all plant reactions such as reversible changes
in plant metabolism, leaf necrosis, altered plant quality or
reduced growth that does not impair yield or the intended use
of the plant (Guderian 1977).
Injury will not occur if [l] the rate of uptake of 0^ is
low enough to enable the plant to detoxify or metabolize ozone
or its metabolites, or [2] the plant is capable of repairing or
compensating for the ozone impacts (Tingey £rTaylor, 1982).
Hill et a_l. (1970) classified the ozone injury into four
general types - pigmented lesions, surface bleaching, bifacial
necrosis and chlorosis.
98 :
The foliar injury has been reported in many plants, e.g.
Zea mays (Kress^ Miller, 1985), and Camissonia claviformis.
C. hirtella. Citrullus lanatus and Erodium cicutarium (Decotean
et al. 1987).
Wood and Davis (1969) found that the development of symp
toms depended on the concentration of ozone, temperature, rela
tive humidity during fumigation, and plant species. Chronic
injury results from the intermittent or continuous exposure to
sub-lethal dose of pollutants. Vegetation exposed to low
pollution level exhibits chlorosis or similar disruptive pig
mentation in leaf tissue.
Acute injury may be caused by exposure to a toxic concen
tration of pollutant for a short duration of time. It is
expressed as necrotic lesions as in Helianthus annuus
(Fujinuma e^ . 1988), and necrotic flecks as in white clover
(Becker ^ » 1989). Both chlorotic and necrotic lesions were
found in Triticum aestivum (Makay et a^* 1987).
Stomatal opening of many plant species is reduced in
presence of ozone (Hill, 1967; Macknight, 1968). The excessive
exposure to ozone causes hypertrophy in certain plants (Hill ejt
al» 1981). The radial growth in Pinus jefferyi was also decre
ased (Paterson £t j[i« 1988). The stem tissue in Gossypium
hirsutum L Mc Nair 235 remained unaffected (Miller et_ _al. 1988).
: 99 :
Ozone stress inhibits photosynthesis (Heath, 1980;
Koziol-^ Whatley, 1984; Reich .: Amundson, 1984) and alters
photoassimilate partitioning. There is generally less phyto-
synthate translocated to root and to reproductive organs
(Oshima a_l. 1978; Oshima, 1979). The altered photosynthate
partitioning was reflected in 0^ inhibition of root versus top
growth (Tingey, 1977; Blum -8; Heck, 1980). It can be summarized
that Oo depresses photosynthesis and alters photosynthate pool
and partitioning among plant organs, which results in retarded
growth. McLaughlin and McConathy (1983) suggested a mechanism
by which 0-, stress alters photosynthate partitioning. This
includes malfunction in phloem loading processes, increassed
allocation to repair damage within leaf itself, and an altered
balance of source and sink caused by a reduced phosynthetic
Carbon fixation and the greater demand for assimilate at the
source (leaves).
Depression in photosynthesis due to ozone exposure was
reported in Ladino clover (Blum ejt aj^. 1983), mycorrhizal
Festuca arundinaceae (Ho - Trappa, 1984), Triticum aestivum
L. cv. Albis (Lehnherr _et aJ. 1987), Triticum aestivum Lona
(Amundson et. al. 1987), Pinus strobus (Reich ejt . 1987) and
Medicaqo sativa (Cooley-^ Manning, 1988). The photosynthetic
rate, however, remained unaltered in Fragaria X Ananasse
(Takemoto et. aj,. 1989), Ozone decreases leaf water potential
: 100 :
as in Petunia hybrida cultivar (Elkiey Ormord, 1979b) and
.caused water stress. This decreases photosynthesis by reducing
the stomatal conductance and the enzymatic activities of carbon
dioxide fixation (Hasiao, 1973). In addition, photosynthate
translocation is also reduced. Stomatal conductance decreases
on exposure to ozone in yellow popular seedlings (Chappelker
et al« 1988) and causes stomatal closure in Satsuma mandrum
(Citrus unshicc) (Matserslima ejt . 1985). However, transpi
ration rate increases in Vicia faba (Agarwal et. aj,. 1985), and
water efficency (Wue) increases in Raphanus sativus and Glycine
max (Carol et_ ajL. 1988). In Glycine max, ozone decreases both
stomatal and mesophyll conductance to carbon dioxide (Yingajaval,
1976). These studies indicate that ozone affects photosynthesis
through several mechanisms.
Lethal concentration of ozone reduced net primary pro
ductivity of Vicia f aba (Agarwal et. . 1985) and net assimi
lation rate in Gossypium hirsutum 1.0shima et. a^, 1979),
Dactvlis qlomerata. Lolium perenne and Phalaris aqutica (Hors-
man et_ al, 1980), Trifolium subtarraneum and T. repens
(Horsman et. .al. 1982) and Liriodendson tulipif era (Jensen,
1985). The reason behind the reduction in net assimilation
rate was attributed to low carbohydrate prodcution in the
stressed trees in case of yellow poplar (Liriodendron tulipi-
fera) (Jensen, 1985).
: 101 :
Foliar pigment concentration is also affected by ozone.
A decrease in chlorophyll level is widely known (Craker &
Sterbuck, 1972; Miller e^ jil. 1973; Leffler J6r Cherry, 1974).
Ozone reduces chlorophyll content in soybean (Pratt-^ Krupa,
1^81), Vicia faba (Agatwal et_ al» 1985), Raphanus sativus cv
'Scarletgbbe* (Johnston et. al,. 1986), Triticum aestevum cv
Albis (Grandj ean J2. Fuhrer, 1989, Lehner jet . 1987; Medicago
sativa (Takemoto et. aj,. 1988) and red spruce (Alscher et al.
1989). The chlorophyll content remaines unaltered in Fraxinus
americana and F. pennsvlvanica (Catherine et al, 1987). Also,
an increase in the chlorophyll content was found in Acer
saccharum and Quercus rubra (Reich, 1986). Genotypic differences
between the populations studied and the differences between
ferigation procedures accounted for some conflicting results.
Ozone alters carbohydrate metabolism. Under normal con
dition, plants produce excess carbohydrates which are translo
cated to roots (McCool-€. Menge, 1983). Under the ozone pollu
tion, this flow is reduced or stopped due to reduction in
carbohydrate level. Carbohydrate was reduced in elm (Ulmus
americana) (Costantinidon'^ Kozlowski, 1979), and Trifolium
repens (Blum et, _al.. 1982). Carbohydrate translocation to bean
root declined (McLaughlin McConathy, 1983; Okano et al.
1984).
: 102 :
The pollutants directly affect loading and translocation
of carbohydrates (Noyes, 1980; Teni^ Sawnson, 1982). Such an
interference with the active phloem loading processes might
result in excess sucrose retained in leaves as in pine (Tingly
jet ai. 1976) and bean (Ito et. al. 1985). Ito et. . U985)
found that ozone decreased, the absolute level of sucrose and
that this inhibited translocation. Ozone fumigation signifi
cantly reduced strach in Fraxinus pennsylvanica (Jensen, 19«2),
Medicaqo sativa (Cooley £L Manning, 1989) and Trif olium repens
(Rebbeck _et. a_l. 1988), starch and sucrose, in green ash seedlings
and tomato (McCool<^ Menge, 1983) and starch and ascrobic acid
in Vicia fabc\ (Agarwal e;t. aJL. 1985), while no effect on energy
reserve (Starch) could be detected in Festuca aroundinaceae
(Rebbeck et_ . 1988). On the contrary, ozone treatment increases
the amount of reducing sugars in potato tuber (Pell _et al. 1980;
Pell-^ Pearson, 1984). This increase, mostly in hexose, would
provide a substrate for respiration and may account for an
increased respiration observed with ozone treatment. These
changes are interrelated and indicate either inhibition in
starch synthesis for hexose or a stimulation in the breakdown
of starch. Koziol (1984) pointed out that an increase in
sugars at the expense of storage starches is a common phenomenon
in plants under air pollution stress; However, there was no
change in the foliar starch content and root carbohydrate
content in red spruce seedlings (Alscher et. al,. 1989).
: 103 :
Due to ozone fumigation, the soluble protein content
declines in Vicia f.aba (Agarwal et_ ad. 1985) and Triticum
aestivum L. cv. Albis (Lehnher e_t al. 1987; Grandjean Fuhrer,
1989). Ozone causes water stress which readily and reversibly
alters protein synthesis, inducing polysome dissociation and
accumulation of amino acids including protein (Hasiao, 1973).
The biochemical studies show that ozone inhibits an
enzyme (Ribulose 1.5 biphosphate carboxylase) that catalyses
the assimilation of C0„ (Pelli^ Pearson, 1983). In Triticum
aestivum (Lehhber et . 1987), ozone decreases activity of
ribulose biphosphate carboxylase/oxygenase, ribulase biphosnnate
and adneylates, triphosphate and 3-phosphoglycerate, while
increases the ration of ATP to HDP and of triphosphate to
3-phosphoglycerate. Ozone exposure also increases peroxidase
activity in Nicotiana tobaccum (Petolino et_ a_l. 1983).
Sublethal concentration of ozone reduces uptake of mineral
nutrients in Vicia faba (Agarwal et. . 1985) and the foliar
concentration of nutrients like calcium, magnesium, iron and
manganese. While it increases the concentration of potassium,
phosphorus and molybdnum in pods, there was no change in rracro
nutrients in Phaseolus vulgaris L. cv. Bush Blue lake 90
(Tingey et aj.. 1986).
Ozone fumigation reduced Hill activity in Triticum
: 104 :
aestivum (Christopher _et aJL. 1987), while there was no change
in the electron transport system in red spruce seedlings
(Alscher £t al,, 1989). Ozone exposure increases free radicals
associated with photosystem I (Rowland _et aj.. 1970J. In Spinacea
oleraceae. ozone inhibition of photosynstem II was attributed to
the system's inability to accept electrons from water (Chang &
Heggestad, 1974). Using isolated chloroplast, Coulson and
Heath (1974) found that ozone reduces electron flow more in
photosystem II than in photosystem I.
The sequence of physiological effects produced by ozone
includes (l) increase in permeability of membrane and lekage
of ions (2) stimulation of stress ethylene production (3)
decrease in photosynthetic carbon dioxide fixation, (4) inacti-
vation of enzymes, and (5) alteration of metabolic pools
(Tingey, 1977), If thp repair process cannot successfully over
come these changes, then foliar symptoms develop, growth gets
reduced, leaf senescence is altered and yield is decreased.
In water, ozone decomposition products include hydroxyl,
hydroperoxyl, superoxide anion and other free radicals (Weiss
1935; Horgue <£ Baden, 1975; Peley 1976). These products are
more powerful oxidants than parent compounds.
Plasma membrane is the site of ozone action, and the
specific sites which are associated with osmoregulatory processes
: 105 :
are most sensitive (Heath, 1980). Ozone and its reaction
products pass through plasma membrane and affect subcellular
organelles and their processes (Mudd, 1982). Ozone, on entering
stomata, contacts the cytoplasmic membrane and affects membrane
structure and permeability.
Ozone appears to affect reproductive processes, decreasing
yield components. It alter photoassimilate partitioning and
may thereby reduce yield. Such a reduction is primary when pho
tosynthesis gets reduced and secodary when number and size of
fruits are reduced.
Reduction in yield was found in soybean (Glycine max)
(Howell jet aJL. 1979; King et_ al. 1982; Endress Greenwald,
1985; Amundson et, aj . 1986), Dactylis qlomerata. Lolium perenne
and Phalaris aquatica (Horsman e^ a_l. 1980), bean (Heggestad
Bennett, 1981), Phaseolus vulgaris (Kohut Laurence, 1983;
Adomait et^ . 1987), Panicum liliaceum (Agarwal et ^ . 1983),
radish (Ashmore, 1984), Oryza sativa (Nishi ejt aj,. 1985),
Lactuca sativa (Temple _et. al. 1986), Triticum aestivum cv, Vora
(Amundson et aJ,. 1987), alfalfa (Temple et. aj,. 1987), Medic ago
sativa (Takemoto £t . 1988) and Triticum aestivum cv. Albis
(Grandjean <S Fuhger, 1989). In Zea mays, seed weight and seed
number also are reduced (Kress <S Miller, 1984).
: 106 :
Ozone causes both acute and chronic changes in yield or
productivity (Kxupa £: Manning, 1988). Reduction in,.yield is
due to a decrease in number of fruit per plant rather than a
reduction in size of the individual furit. A significant
reduction in number of the reproductive organs has been reported
for wheat (Spencer S. Letchworth, 1979) and push bean (Heggestad
et aX' 1980).
In case of soybean, ozone decreases various components
like pods/plant, filled pods/plants, seed/plant, seed weight/
plant and weight/seed (Howell jet. al. 1979; Heagle <& Letchwerth,
1982; Kress<^ Miller, 1983; Reich Amunason, 1984; Unsworth
_et al. 1984; Damicone, 1985; Endress <Sr Grunwald, 1985). In
case of Avena sativa, it reduces vegetative yield/head, number
of tillers/head, seed/head, seed weight/head, number of seed/
head, bushels/head or harvest index remained unchanged (Pall ^
Puente, 1987).
Seed size and seed dry weight got decreased in Triticum
aestivum (Amundson e_t . 1987).
FLOURIDE (F)
Flouride is one of the most exploited elements during
the second half of this century. This is a cummulative
pollutant whose concentration keeps on increasing in an eco
system with time and once introduced into the system its
cycle continues in an unending manner.
Chemical compounds containing flouride are common cons
tituents of earth's crust. Minerals such as flourspar (CaF)
cyrolite, and flourapatite are the major sources of flourine.
Active volcanoes are the natural sources of flouride in the
form of hydrogen flouride, ammonium flouride and silicon tetra-
flouride. Dust and gases containing flouride are released into
the atmosphere durina aluminium and steel production. It is
also produced in the manufacture of bricks, tele proauction,
superphosphate fertilizers, in the combustion of coal and in
various other less important processes.
In Czechoslovakia, the average flouride content of coal
is as low as 0.01% but more than 10,000 tonnes of flourides
are released annually into the atmosphere.
: 108 :
The problem of flouride pollution has grown worldwide
due to expanded use of aluminium, coal and fertilizers. Heck
et al. (1973) ranked flouride fifth in importance after ozone,
sulphur dioxide, oxidants other than ozone and pesticides with
respect to the amount of plant damage produced in the United
States.
Flouride is the most phytotoxic of the common pollutants
and the susceptible species can be injured at the atmospheric
concentration 10 to 100 times lower than those of the other
major pollutants. The problem of airborne flouride (F) in
agriculture and forestry were known in Europe for many years
before being recognized in the United States. The primary
gaseous forms of flouride are hydrogen flouride and silicone
tetraflourlde.
Most vegetation characteristics were altered in areas of
high pollution. It was stated that flouride pollution is quite
significant in North America, and there have been reports of
damage to plants from Tenesse (Maclntire, 1952), New Jersy
(Daines et aj,. 1952) and California (Middleton £t ^ . 1965).
During the late minteenth century, German workers des
cribed the flouride damage to flora near copper smelter
(Schroeder J Renss, 188'^), super phosphate production centre
(Mahyrhofer 1893| Rhode, 1895; Wislieenus, 1098) and glass
: 109 :
processing and fertilizing factories (Ost, 1907). Later on,
various reviews concerning the flouride damage appeared in the
European literature (Haselhoff ejt aJ. 1932; Romell, 1941).
Cases of flouride injury were reported by Gisiger (1955);
Scurfield (i960), Holte (1961), Garber (1963) and Bossavy (1965b)
Different species of plants exhibit a wide range of toler
ance to flouride (Weinptein, 1977). According to Tendron
(1964), highly sensitive species include English walnut, Spanish
chesnut (Castanea sativa Mill) and paulomnia (Paulownla species),
while English elm, black alder (Alnus qlutinosa. Gaerth),
American mountain ash (Sorbus domestica Marsh), European alder
(Sansbucus nigra L.) and European linden (Tilia cordata Mill)
were tolerant. Conifer species including Dauglas fir, western
larch, white spruce and eastern white, pondesora and lodgelole
pines were most sensitive. Weinstent and McCune (1970)
summarized the effects of flouride on the dictoyledonous plants.
Several other reviews also bring out the effects of flouride
on plants (see Thomas and Alther, 1966; Weinstein and McCune,
1970; 1971; Chang, 1975; Growth, 1975; McCune, 1976; Weinstein,
1977, 1979; Amundsen J? Weinstein, 1980).
Flouride Injures p Lants due to its accumulation in the
plant tissue over a period of time. The extent and degree of
injury depend upon specie, varietal differences in susceptibi
lity, the concentration form of flouride, duration of exposure
: 110 :
and the overall modifying aspects of the total environment.
Inside the leaves or twigs, flouride dissolves in plant liquid
and moves in the transpiration stream to its principal site of
accumulation at the tip and margins of the leaves (Hommel,
1941; Ledbetter, et_ aj,. 1960; Jacobson _et al,' 1966) causing
foliar injury. Highly 'Susceptible species like conifers, glaai-
olus, Chinese apricot, oregon grape or goatweed exhibit foliar
lesions on accumulation of even low concentration of flouride.
In contrast, cotton, tea, camelia, nickories and flowering
dogwood can accumulate high dose of flouride without any foliar
injury (Zimmerman Xr Hitchcock 1956; Zimmerman et_ al. 1957;
Jacobson et. a^. 1966; McClenahen, 1976).
The injury usually results from a gradual accumulation of
flouride in the plant tissue over a period of time. Foliar
injury was reported in four rice varietes (Cho _et. a_l. 1985)
and grape leaves (Murray, 1985) due to fumigation of hydrogen
flouride, in Rasberry and blue berry (Shaniforth _et aJ . 1984)
and in Solanum pseudocapsicum. Jerusalan and Cherry (Maclean
et. aX' 1984).
Brewer et, jaj.. (I960) showed that older leaves can develop
tolerance and that young leaves seem to accumulate flouride
for a time before symptoms chlorosis and necrosis occurred.
Fumigation with a high concentration flouride for short period
: 111 :
causes acute injury in the form of interveinal and marginal
necrosis. Necrotic spots of red brown colouration developed
on the leaves of certain grasses after fumigation with HF
(Oin ejt aJ. 1981). Exposure to flouride caused tip and margi
nal necrosis in tulip and gladiolus (Hitchock et aj.. 1981),
Tulip qeneriana and Sorohum vulqare and yellowing and mottling
in rice plants (Sun J Su, 1985).
Chronic injury results from exposure to low concentration
of flouride for a short r*uration of time. Flouride caused
chlorosis, necrosis, needle damage and defoliation in Abies
balsanea. Picea moniana and Horize loricina (Staniforth _et al.
1984).
If injury is more severe than chlorotic, the spots change
to a necrotic one mainly between thicker veins or the tip of
the leaf. Exposure to flouride also delays leaf fall in
Rasberry and Blue berry (Staniforth ejt a_l, 1984).
Flourides at sublethal level affected growth (Hitchcock
^ aj;. 1964), by either stimulating or checking it. The growth
increases in more tolerant plants. Chang (1970) observed that
flouride decreased thr number of ribosomes and damaged the
structure of ribosomal protein, thereby affecting negatively
the entire protein synthesis and consequently retarding the
growth. It also caused reduction in leaf weight and leaf surface
: 112 :
area (Murray . Wilson, l'?88), bunch weight and number of
branches in grapes (Murray, 1985).
Both aqueous and particulate flourides are deposited on
the leaves and other plant surfaces, while gaseous flouride
enters the stomata, passes into the intercellular space and
is absorbed by the mesophyll (Thomas A Hendricks, 1956). It
induces injury in the mesophyll and guard cells, and damages
cell membrance (Zwiazek-^ Shay, 1988). Phloem and xylem paren
chyma cells on exposure to flourides become enlarged and dis
torted (Qin et. al. 1981).
Even a very low concentration flouride brings aoout
changes in the plant metabolism, causing listurbance in plant
photosynthesis and decreasing leaf productivity (Bonte, 1982).
Photosynthetic leaf area decreased in Terminalia tomentoso
and Buchananla lazan on fumigation with hydrogen flouride
(Pandey, 1985).
Fumigation with flouride affects magnesium present in
the chlorophyll, thus simultaneously affecting chlorophyll
content in the leaves of the affected plants in Terminalia
tomentosa and Buchanania lanzan (Pandey, 1985) and grape
(Murray, 1985). ChJorophyll b was found to be more aftectr-d
than chlorophyll a in Prosopis 1uliflora. Acacia nelotia,
: 113 :
Calotropls procera and Zizyphus nummularia (Pillai eJt al.
1985).
Gaseous flouride is absorbed by stomata of the leaves
and affects the stomatal conductance. Hydrogen flouride
increases the stomatal conductance in the leaves of eucalyptus
(MurrayA Wilson, 1988).
Hydrogen flouride had a significant effect on the potential
alcohol content, water content and leaf protein concentration
in grapes (Murray, 1985), the energy content was found to de
crease in Terminalia tomentosa and Buchanania lanzan (Pandey,
1985).
On fuming fumigation with flouride, the rate of flouride
accumulation increased in Vitis vinifera (Doler _et aj,« 1984).
The flouride content of leaf blade was about three times
greater than that of stems and petioles combined. Greatest
accumulation occurred in the roots. In general, broad leaved
trees accumulate more than conifers (Sindhu 1977, 1978).
Flouride accumulation decreases from the upper to lower epidermi?
(Garrec et. aj.. 1973). Chloroplasts are the site of the highest
flouride accumulation (Chang -i Thom^gon, 1966), palisade
parenchyma are also said to have a heavy concentration of
flouride.
Hydrogen flouride Inciuces ultrastructural chdncies In
chloroplast morpholcty. The Interndl memorane ot the cnloro-
114
plast is dilated and the total amount of green membranous
material per cell is reduced (Harvath et. ad,. 1978).
Flouride brings about a number of genetic changes in
plants. It was postulated long back by Mohamed (196'S') that
fumigation with flouride increases the frequency of chromosomal
aberration. It also has a specific effect on fertilization
(Pack, 1966, 1971, 1972; Sulzbach Pack, 1972; Pack A,
Sulzbach, 1976).
Hydrogen flouride was found to reduce yeild in wheat
(Maclean -^Schneider, 1981), four varieties of rice (Cho, ejt
a^. 1985) and the grape (Murray, 1985).
Several studies have been conducted on the effect of
flouride on seed germination (Navara, 1964; Holub ^ Navara,
1966; Navara aJ. 1966). The percentage of germination of
seeds decreased in Abies balsama. Picea moniana and Horizi
laricina (Sidhu aj,. 1986).
Plants growing in the atmosphere polluted by flouride
compounds show a defective fruit formation (vKeinstein, 1977);
per cent deformation and the number of undeveloped seeds in
creased in pea (Bonte ejt jj,. 1980).
A continous exposure to flourinated compounds totally
inhibited seed production in soybean, but no effect could be
: 115 :
detected on cotton. Bell pepper, sweet corn, cucumber, peas,
sorghum, oat, wheat and barley lie between these two species
in a decreasing order of sensitivity (Pack A Sulzbach, 1976).
Exposure of Abies balsama. Picea moniana and Horizi
lariciana to flourine resulted in reduction the seed size,
number of seed/cone, number of cone per tree, number of fertile
tree and size of cones (Sidhu et_ . 1986). Likewise, resberry
and blue berry showed a reduction in seed production, size,
number and dry weight of fruit, and a severe flower mortality
and reproductive potential (.Staniforth e_t aj,. 1984).
ACID RAIN
The areas affected by gaseous pollution are also sub
jected to acid precipitation. The pH of unpolluted rain is
generally given as 5.7. While pH of precipitate falling in
North and Central Europe, and the Western section of U.S.A.
has been recorded to range from 4.0-5.0 (Rambo, 1978; Pack,
1980). In the North eastern United States and the adjacent
portion of Canada, it ranges between 2.0 and 3.0.
The term 'acid precipitate' has come to mean mainly
precipitate (rain, snow, dew etc.) containing significant
quantity of strong acid form of certain pollutants, suffici
ent to produce a pH in precipitation lower than that of un
polluted rain. The chief pollutants contributing to precipi
tate acidity are oxides of sulphur and nitrogen. The oxida
tion of sulphur dioxide and nitrogen oxides leads to the
formation of sulphuric and nitric acid and particulate
sulphates and nitrates, respectively (Smith, 1981).
SOx originate as a byproduct of coal combustion, mineral
smelting and to a lesser extent of petroleum refining and
combustion. About 90% of the sulphur in the atmosphere of
North eastern United States comes from the anthropogenic
: 117 :
sources (Galloway ^ Welpdale, 1980). About 93% of the anthro
pogenic sulphur production occurs in the Northern Hemisphere
and about 805 of this total is deposited on land surfaces in
that hemisphere (Friend, 1979), One half of the atmospheric
sulphur reaches the earth's surface in wet precipitate (Wet
deposition). Most sulphur occurring as sulphate is found asso
ciated with H" , NH " ions (Nrdo, 1976).
The nitrate compounds resulting from NO emission are
believed to account for more than 40? of the acid precipita
tion in the USA and Ca 35% in Western Europe (Chadwick, 1983).
Nitrogen compounds generally produce nitric acid (HNO-). In
the Adkrondack Mountain region, 34% of the anions in rain were
found to be the contribution of nitrates (Stensland, 1983).
Another strong mineral acid causing acidity in orecipitation is
hydrochloric acid (HCl). Galloway e_t . (1982) gave a compre
hensive review of the scientific literature on the occurrence
and variation of different ions in wet depositions.
Acidification is very damaging to aquatic exosystems;
effects on terristrial vegetation underfield conoitions are
much less documented than aquatic impacts (Hileman, 1982).
Various studies have attributed the damage to vegetation and
reduction in forest productivity in the affected areas to
acidified precipitation (see Jonsson, 1977; Binns X Redfern,
: 118 :
1983). Several reports have appeared on the response of
vascular plants to acidic deposition (see Jacobson, 1980;
Haines ejt al.. 1980; Shriner, 1980; Evans, 1982; Raynal et,
^.1982; Ulrich, 1982; Percy, 1983 etc.), mostly dealing with
European and eastern North American species.
Several coniferous forests in Germany and Scandinavia
have been destroyed due to 'acid rain' (Van Breeman, 1985;
Paces, 1985). Fir is the most badly damaged species followed
by pine, spruce and beech (see Binn, 1984, Wetstone Foster,
1983).
Plant species differ in response to simulated acidic rain,
mainly because of differences in macroclimate and/or micro
climate. Plants rank in their sensitivity from high to low in
the following order : herbaceous, dicot» woody dicot, monocot
and conifers (Evans iL Curry, 1979; Evans, 1980).
Decrease in growth due to acid rain was observed in
Phaseolus vulgaris (Blum -i Heck, 1980; Johnson et. . 1982;
Battey, 1988), Pinus riqida. P. echinata and P. taeda
(Johnson _et . 1981), Acer saccharum and Quercus rubra (Reich
et al. 1986), Pinus jeffreyi and Sequoia qiqantia (Temple,
1988) and Brassica oleracea (Takemoto et_ . 1989). A
decrease in height and diameter growth was noted in Picea abies
(Tveite, 1980). This showed a strong stastical relationship
: 119 :
between growth rate and acid precipitation. Various evidences
indicate that plants are not directly affected by acid rain.
Rain acidity may affect soils with poor buffering capabilities
and thus indirectly influence plant growth (Amthor, 1984).
There was no effect on growth of sugar maple and northern
red oak seeds (Reich aj.. 1986), Soybear (Elliott et aJ. 1987)
and seedling of Picea rubra (Battey, 1988). Shoot growth remain
ed unaltered in Fraxinus americana and F.. pennsylvanica
(Catherine e_t . 1987) and Acomastvlis rossi (Funk <£ Bonde,
1986).
Interestingly, some botanists hold that acid rain benefits
forests through some fertilizing effect associated with its
— 2—
nitrate (NO,, ) or even sulphate (SO. ) content. Such a view
has emanated from certain studies made on jack pine, white
spruce (Abouguendia Baschak, 1985), Pinus stobus (Wood *
Bromann, 1976, 1977) and some other species (Raynal e_t . 1982).
Simulated acid rain causes reduction in plant weight in
Phaseolus vulgaris (Hindawi _et. aJ. 1980), in root dry weight
in raddish (Olson _et . 1987) and in dry mass of stem and
leaves in soybean (Evans, 1980) and pinto bean (Evans Lewis,
1980). There was no alteration in stem weight in Glycine max
(Johnson _et aJL. 1986) and root mass in Raphanus sativa (Evans
et ^ . 1982).
: 120 :
The acidity has deletrious effects on foliage. Many
species of Sphagnum vanished in the Pennine region of U.K.
possibly due to b'isulphate ions present in rains (Lee -2. Bell,
1978). Acid precipitate causes foliar injury in Beta vulgaris
(Evans aj . 1982), Phaseolus vulgaris (Johnson _e_t aj . 1982),
Cucumis sativus (Jacobson £t ^ . 1987), Allium sepa. Citrus
sinensis. Lvcopersicum esculent urn. Medicago sativa. Phaseolus
vulgaris. Poncirus trlfoli ate. Raphanus sativa and Spinaceae
oleraceae (Musselman ^. Sterrett, 1988), Pinus 1effreyi and
Seguoia gigantia (Temple, 1988) and Fragaria ananassa (Takemoto
et al» 1989). Raphanus sativa (Evans _et. a_l. 1982) remained
unaffected, while weak chlorosis developed in needle and the
wax layer got badly damaged in Picea abies (Nengel _et, ail. 1987).
The injury appeared in the form of undesirable leaching
and cuticular erosion, chlorotic and necrotic lesions. Number
of affected plants and needles increased with rain acitity and
with time in white spruce (Picea glauca) (Abounguendia ^
Baschak, 1986). Foliar damage also includes interference with
normal functioning of the guard cells and poisoning of plant
cells after diffusion of acidic substances through the stomata
or cuticle (Tamm ^Cowling, 1976). Galls were produced from
abnormal cell prolification (hyperplasia) and abnormal cell
enlargement (hypentrophy) in Artemisia tilessi. Phaseolus
alleghaniensis (Paparozzi ^ Tukey, 1980) small round lesions with
: 121 :
necrotic edges formed on young leaves. Injury occurred more
frequently near the vascular tissues and trichomes. The
amount of injury on plant foliage is correlated to the area of
leaves in contact with rain water as injury depends upon the
rate of absorbtion of materials from rain water per unit area.
The amount of water absorbed by foliage depends upon many cha
racteristics that vary among plant species, and as a result may
determine relative specie sensetivitypto precipitation acidity.
Lesions produced by simulated acidic rain occur mostly on
leaves and reproductive structures (Evans Curry, 1979).
Visible injury in leaves is most pronounced on foliage of certain
species just prior to full leaf expansion (Evans *^-Curry, 1979;
Evans 1980, 1982). Exposure to acid rain increases leat drop in
Medicaqo sativa (Takemoto jjt aj,. 1988).
Acidic precipitate, after diffusing through stomata or
cuticle, may affect photosynthetic efticiency. Retardation in
photosynthesis was reported in alfalfa (Temple e^ aj,. 1987),
Brassica oleracea and Fraqaria ananassa (Takemoto, _et aJL. 1989).
The photosynthesis was, however, unaffected in Acer saccharum
and Quercus rubra (Reich e_t . 1986), and so was the transpira
tion in Glycine max (Takemoto et. . 1987).
The foliage exposed to acidic rain may be more sensitive
to exposure to gaseous air pollutants. This decrease in resis
tance mey increase C0„ uptake for photosynthesis.
122 :
Effects of acid pollution on metabolic processes resulted
in decrease in chlorophyll content (Jaakkola et_ a_l. 1980) in
Phaseolus vulgaris (Hindwai et, a^. 1980) and Medicaqo sativa
(Takemoto et_ al. 1988), though there was no significant change
in chlorophyll content in Fraxinus americana, F_. pennsylvanica
(Catherine et, a^. 1987), and Glycine max (Takemoto et aj,. 1987),
The acidic deposition also has a negative effect on respi
ration and water conduction. Since the guard cells were prefer
entially affected, it was postulated that acidic precipitation
affected the rate of gas exchange by stomata (Tamm J^ Cowling,
1977), The stomatal conductance was decreased in alfalfa
(Temple £t a^. 1987) and yellow poplar seedlings (Chapoelka e_t
al, 1988) but no effect was apparent in Glycine max (Takemoto
et. aJ,, 1987). CO^ assimilation was inhibited in Brassica
oleracea (Takemoto e_t aJ,. 1989).
The ambient rain caused reduction in nodulation ani the
total nitrogen content in Phaseolus vulgaris (Blum . Heck, 1980)
but there was no effect on the concentration of elements in
leaves of Glycine max (Takemoto e_t aj,. 1987).
The effects of acid precipitate on soils were concerned
+ 2— largely with the reactions of H or SO^ and to a lesser
degree of NO-,'" ions. The chemistry of acidit ication, wnich
involves replacement of base cations (K" , Ca , Mg , Ma"*" etc.)
on exchange sites on particle surfaces with H"*" ions and at lower
: 123 :
pHs with solubilized aluminium (Al ) ions as well, is relati
vely well understood and has been described by various writers
(Wiklander, 1974/74, 1975, 1980; Bache, 1980a and othf-rs).
The acid rain affected yield of alfalfa, wheat and lettuce
(Evans et_ aj.. 1982) reducing it markedly in pinto bean (Evans,
1980), radish root (Lee et sd. 1981; Evans £t aJ,. 1982), Beta
vulgaris (Evans ejt a * 1982; Evans et. aJ,. 1984; Banwart e_t al.
il984), alfalfa (Medicaqo sativa) (Temple et. aj,. 1987; Takemoto
ot al. 1988), feild corn (Banwart et. ai. 1988) and Zea mays
(Banwart et. al,. 1988; Lyle A Waldron 1989). The yeild of soybean
was unaffected (Norbv .et. a_l. 1985; Johnson 4: Shriner, 1986;
Elliott ei .ai* 1987). The acid rain decreased the number of nods
per plant and number of seeds per pod in pinto bean (Evans, 1980)
and Phaseolus vulgaris (Blum -<, Heck, 1980). A decrease in seed
yield resulted from the decrease in the pod number per plant,
suggesting that plant reproduction may be affected. A decrease
in the number of pods per plant may result from a decrease in
flower pollunation (and fertilization), a decrease in pod reten-
sion, inadequate development of young pods, or pod abrotion
caused by lack of nutrients.
COx (1982) studied pollen germination and pollen tube
elongation in some eastern Canadian species, including nine
forest trees under the impact of acid rain. Broad leaved trees
such as Acer saccharum. B. papyrifera and Populus tremuloides
: 124 :
were more sensitive to acid precipitation than were conifers
such as Picea mariana. Pinus banksiana and P. resionsa.
Pollen germination was reduced in Zea mays (Forsiine £t
al.l982, 1983; Wertheino ^. Craker, 1988; Lyle 4. Waldron, 1989J
and pollen tube growth was inhibited in Picea qlauca (Sidu,
1983) and Zea mays Uyle ^.Waldron, 1989).
In Cucumis sativa. acid rain causes reduction in the
number of the female flowers produced, dry mass of the flower
and immature fruit but there was no change in the number or
weight of fruits (Jacobson e_t . 1987j. In Populus tremuloides.
acid rain increases fruit abortion but reduces the number of
seeds per fruit and the percentage of placenta (Cox, 1988).
Lee and Weber (1979) found seedling emergence to be higher
under the influence of acid rain in Eastern white pine, Pinus
strobus. yellow birch (Betula alleqhaniensis) eastern red cedar
(Junipeius virqiniana) and Douglas fir (Psuedotsuqa menziesii)
but lower in Staghorn sumae (Rhus typhina).
Inhibition in germination was reported in Acer rubrum and
Betula lutea (Raynal ejt aJ. 1982), but no significant effect
was found on sugar maple (Acer saccharum) (Raynal _et. aj . 1980),
Acomastylis lossi. and in bulblets of Bistorta vivipara (Funk al
Sonde, 1986).
125 :
From the available data it appears that seedling germi
nation and emergence can occur over a wide range of substrate
pH level. The acidic precipitate may directly or indirectly
affect productivity of the crop and forest plants.
PARTICULATE POLLUTANTS
Pollutants emitting from various anthropogenic and natural
sources comprise both gaseous and particulate pollutants.
There is no sharp line of demarcation between the gaseous and
particulate matters in the air. No place on the earth and in
the atmosphere can be envisaged 'particulate free' as they are
present in the whole of the natural environment.
The particles differ in shape, size and composition with
reference to their mode of origin, growth, interaction dna
decay (Corn 1968) .
The particulate matters in the atmosphere can be classi
fied as Aitkin nuclei (less than 0.01 (im) and aerosols (0.01 jam
size). Fine particles lie between the size ran je ol 0.01 ^m
and roughly 3,0 |im, whereas coarse particles are greater than
roughly 3.0 |im.
Aerosols from 'mist' with liquia particles and 'cust*
with solid particles, regardless of the particle size (Corn,
1968) while smoke refers to the by-product of combustion.
Three major type of dusts were recongized by McCorne et. al.
(1967). The first consists of wind erosion oarticulates which
: 127
are mostly inorganic substances like soil, rock and minerals
that are considered to be harmless to vegetation. The second
type consists of industrial dust, possibly phytotoxic as this
is a product of refining industries, foundary opprations,
cement and glass industries. The third one comprises of coal
dust (solid particles) and fly ash which are highly dpter-
mental for the living woild.
Large amounts of dusts are emitted into the atmosphere
from the numerous thermal electric plants and combustion pro
cesses using low grade coals. Emissions from coal combustion
comprise various quantities of particulate matters composed of
different metals (Gordon, 1983).
Mectham (1952) estimated that from the annual combustion
of 180 million tonnes of coal in Great Britain, 0.6 million
tonnes of ash, 2.4 million tonnes of smoke and b.2 million
tonnes of sulphur dioxide per year are releasee into the air.
Katz (1956) estimated a dust fall of 67.b, 61.2 and 33.3 tons/
mile/month for New York, Chicago and Los Angeles, resrectively.
With the present rate of coal consumption in the thermal power
plants, an estimated 12.21 million tonnes of fly dsh is releaspiJ
into the atmosphere, of which nearly one thlra jor s into the
air and the rest is oumped on lano oi in water (Fulekar e_t al.
1982). Rai (1984) observed that three power plants or Delhi
: 128 :
(Rajghat, Indraprashtha and Badarpur) consumed 2,CXX)-2,800
tonnes coal and released 6.00 tons of fly ash daily. Each ton
of the coal ash constitues seventy elements including 700 gm
nickel, 500 gm arsenic, 500 gm germanium, 400 gm uranium,
300 gm cobalt, 200 gm tin, 100 gm lead, 20 gm bismuth and 5 gm
cadmium (Puri Katyal, 1984).
In cement, dust particles range from 0.1 to 100 pm in
size and form a thick impervious crust on the surface of soil
and vegetation around the factory. Cement dust comprises a
mixture of calcium, potassium, silicone and sodium oxides
(Ambusht, 1989). In comparison to gaseous pollutants, very
few studies have been carried out on the effects of particulate
air pollutants on vegetation (Lerman i$: Darley, 1975).
The soil and vegetation in the vicinity of a cement fac
tory may be variously affected^ depending upon the amount of
dusts emitted in the area. A census carried out on the plants
around the Chanaasi Coaldepot, Varanasi, gave evidences of
coal-aust toxicity to plants (Rao, 1980) . 'Within two years of
its operation, many tree species around the coal depots were
already dead ano many were in the processes of dying. Several
mango trees became dead with their branches completely defo
liated. Cement dust was reported to be harmful to vegetation
in Cdlitornia as early as 1909 (Pierce, 1909, 1910).
: 129 :
The soil near cement factories becomes alkaline and
unfavourable for plant growth. Cement caused reduction in
plant growth (Bokra, 1981) as for example, in populus (Bohne,
1963) and alfalfa plants (Darley, 1966).
Cement dust caused reduction in leaf size of Psinium
qua.j ava. thus bringing down the overall primary production
(Lai A Ambasht, 1980). In Triticum aestivum, cement with NO^
causes a measurable reduction in biomass accumulation (Singh
1980). However, Madhuca indica. Tectona grandis and Butea
monosperma sprayed with fly ash showed increment in dry weight
(Dubey et. al,. 1987).
Necrotic spotting appears on leaves due to the acidity
of the soot particles (Miller^. Rich, 1967). Apart from
necrotic lesions, death or degeneration of epiaermal cells is
also caused by the cement dust. The leaves dusted with flyash
did not show any apparent injury symptoms probably because
flyash was not chemically as active as cement or coal oust.
(Pawar _et. aj.. 1982), In a comparative study of effects of
cement coal dust and flyash on Hibiscus abelmoschus (Pawar _et_
al. 1982) cement dust was found to be most damaging to chloro
phyll; a slight increase was observed on treatment with tlyash.
Leaves sprayed with cement and coal oust exhibited small chloro-
tic spot and marginal chlorosis, while flyash y-'S unable to
to produce any such injury.
: 130 :
Dust particles are usually harmless. However, they pose
a threat to vegetation if they are present at a concentration
sufficient to plug stomata orsmother the leaf, partially or
compiletely or prevent the gas exchange, thus leading to a
disturbed water relation, reduced photosynthesis, and sometime
necrosis in leaves.
The plants growing in the environment polluted frorr: cement
dust showed various alterations in the epidermal features.
These growing in the vicinity of the polluted environment showed
a decrease in size of epidermal cells, and an increase in the
number of epidermal cells and trichomes (Kulshreshtha _e al.
1980) as in Syzyqium cumini (Jafri _et_ _a . 1979), Psidium quaj ava
(Yunus <& Ahmad, 1980) and Ipomea f istulosa (Yunus £t_ aj,. 1982).
Trichome size was reduced in Psidium qua.1 ava (Yunus > Ahmad,
1980). Size of stomata was reduced while stomatal frequency
increased (Kulshreshta e_t . 1980) . In Ipomea f istulosa,
frequency of trichome increased and stomatal opening became
wider with disorganisation of cuticular straition pattern and
dissolution of the cell wall (Yunus et. a^. 1982). Cement dust
affects various physiological aspects of plants by way of leaf
encrustation, stomatal plugging, solarradiation interruption and
alteration and intera, inter and extra cellular pH change in the
leaf. Plants with pubescent surface are more sensitive.
131 :
Cement dust caused reduction in chlorophyll content in
Psidium quqava (Lai / Ambasht, 1980), wheat plant (Sinc h ^
Rao^ 1981) and Hibiscus abdmoschus (Pawar jet, eiJ,. 1982). The
cement dust forms a hard crust on plant surface after nvdera-
tion and crystallization. This layer interrupts dDsorrt,ion ot
light by chlorophyll and lowers the starch formation. A
reduction in the moisture protein, total ash, tat r->no cruc:e
fibre but an increase in the total carbohydrate content in grains
of maize have been observed (Pandey and Simbu, 1988).
Cement dust caused reduction in the rate of transpiration
in wheat plant (Singh Rao, 1981) and in the intensity of res
piration and catalase activity in maize (Borka, 1981). However,
stomatal conductance and transpiration rate increased in
Betula monosperma, Ficus benqalensis and Maqnifera indica
(Reddy aj,. 1988).
In maize, the cement dust caused an increase in r j.iiation
intake, plant temperature and evaporation (Angela, 1986). The
cement dust also hindered the mineral (Nitrogen, Phosphoius)
accumulation in wheat plant (Singh, 1983). It caused reduction
in iron and phosphorus contents and calorific values, but
increased calcium content in maize (Pandey ii Simbu, 1988).
Plants treated with coal dust, through heat imbdlance,
changed the mineral accumulation patterns (Withrow, 1967;
Esptein, 1971).
: 132 :
Cement dust reduces yield and disturbs reproductive
processes especially pollination and fertilization. For
example, a deterioration of fertilization and a decrease
in yield were observed in maize (Angela, 1980). The cement
dust decreased the rate of ear production in maize (Bokra,
1981) and the productivity in wheat (Singh Rao, 1981).
Cement alongwith N0„ caused quantitative and qualitative deter
ioration in wheat grains (Singh, 1980). It was seen that line
coal particles, especially at the time of flov^ering, singifi-
cantly hampered the processes of pollen germination and ferti
lization which are the prerequisites tor fruit setting (Rao,
1971).
PLAN OF WORK
The following plan of work has been carried out
for the comparative study of foliar, stem and root responses
of some crop species to the ambient environment at different
growth phases.
Selection of the Sites :
To make a comparative study of the effect of air
pollution on growth, development and structure of leaves,
stem and roots, certain crop species have been selected.
The materials for the study will be collected from Aligarh
University Campus and Kasimpur Thermal Power Plant Complex,
considering the former as a normal location (Site A) and
the latter as the polluted one (Site B ) . Materials will be
collected from these sites in different seasons.
Aligarh is situated in the Ganga-Ja'muna Doad between
27° 29'N and 28° ll'N latitude and 77° 28'E and 78°34'
longitude. The whole district of Aligarh is located in an
almost uniform level plain, the range of altitude being
622-640 feet. Its seasonal calendar contains a winter
(December-February), a summer (March-Junej, a rainy season
(mid June-September) and a season of the southwest retreating
monsoon (October-November).
134 :
The University Campus was selected as the normal
site since the pollution, if at all, is quite nominal
here. The only source of any possible air pollution
being the light vehicle traffic and sporadic domestic
fuel burning.
The Kasimpuf town is situated about 16 kms. North-East
of the Aligarh city. A Thermal Power Plant came up here
some 41 years back on the banks of an irrigation canal which
flows in eastword direction. Both the university area and
the Kasimpur locality have similar ecological field conoitions
particularly. The edaphic ones. However, Kasimpur is heavily
polluted due to the presence of a Thermal Power Plant Complex
which consists of three power stations 'A', 'B' and 'C having
a capacity of 90 MW, 210 MW and 230 MV . Power generation
respectively. On an average the complex consumes about
1,530,715 metric tonnes of bituminous coal per year (Table III)
The effluents emerging out of the coal burning are a mixture
of many gases, coal dust and ash»
Selection of the Species :
A general survey of the selected sites has been made
and the following crop species growing commonly at both the
study sites have been selected to conduct the present investi
gation.
: 135 :
Crop Botanical name English name Family
Pulse Ca.1 anus ca.1 an L. Red gram Papilionaceae
Cicer arietenium L. Chicken pea
Pisum sativum L. Garden pea
Viqna munqo L. Black gram
Viqna radiata L. Green gram
Oil Brassica campestris L. Yellow Sarson Brassicaceae
Brassica juncea L. Indian mustard
Brassica oleraceae L. var. botrytis L. Cauliflower
Brassica oleracea L.
var. capitata L. Cabbage
Vegetable Daucus carota L. Carrot Apiaceae
Raphanus sativus L. Radish Brassicaceae
Solanum melonqena L. Egg plant Solanaceae
Solanum tuberosum L. Potato
Grain Hordeum vulqare L. Barley Poaceae
Pennistem typhoideum Pearmi It
Triticum sativum L. Wheat
Zea mays L. Maize
: 136 :
Parameters to be Studied :
The following parameters have been chosen to make a
comparative study of the growth responses in the selected
species.
[A] Morphological :
(ij Length of the plant (iij Length of the root
Ciii) Length of the shoot (ivj Root biomdss
(v Stem biomass ^vij Leaf biomass
(vii^ Leaf number/plant (viii) Leaf area/plant
(ixj Per leaf area (x) Leaf fall and emergence
(xi) Leaf length width (xiij Petiole length ratio
Cxiii^ Flowers, fruits, (xivj Injuries (types, extentj seeds/plant
[B] Anatomical :
(a^ Epidermal features :
i) Stomatal index and stomatal frequency
ii) Length and width of stomatal aperture
iii) Length and width of guard cell
iv) Length and width of trichomes
v) Size of epidermal cells.
vi) Gross leaf anatomy
vii) Proportional variation of various tissues.
: 137 :
(b) Stem and root anatomy :
i) Fibre length
ii) Vessel length
iii) Vessel width
iv) Area of cortex
v) Area of vasculature
vi) Area of pith
vii) Frequency of vessel elements in stem and root.
(c) Biochemical :
i) Estimation of chlorophyll
ii) Estimation of N, P, K
iii) Estimation of Sulphur
iv) Estimation of Cu, Fe, Mg, Mn, Ni, Pb and Zn
: 138 :
METHODOLOGY
The morphological, anatomical and biochemical responses
to air pollution will be determined by applying the following
methods.
Morphological Studies :
The plant height, root length and shoot length will be
measured in cm. The shoot length covers the plants axis from
the ground level to the upper most growing tip of the main
axis. For root length, the main tap root will be measured
from the ground to the root tip. The plant height indicates
the length of the entire axis extending from root tip to shoot
tip. The leaf, root and shoot biomass will be determined by
oven drying the material at 80°C for 48 hours and weighing
(in grams) on chemical balance. Leaves will be count ed per
branch and their number multiplied with the total the average
leaf number per plant. The leaf area will be estimated with a 2
planimeter in Cm and the dimensions of petiole and lamina
measured in cm. Flowers, fruits and seeds per plant will be
counted in the flowering and postflowering phases on randomly
selected individuals of each species.
139 :
Anatomical Studies :
The collected samples will be fixed in FAA and trans
ferred to an alcoglycerol (.in case of hard materials viz.,
root, stem) or fO% alcohol (in case of soft materials viz.
leaf) for softening and preservation. To study the anatomi
cal variation within the stem and root, fibres and vessel
elements will be macerated by treating with hot HNO^ (Ghouse^.
Yunus, 1972). The slices of wood, would be taken from the
third internode, and that of the root from 1 cm. below the
ground. Of the macerated elements, 50 vessel members and 100
fibres per sample will be measured at random with the aid of an
ocular micrometer scale. Transverse sections of stem and root
samples will be obtained on a Reicherts sliding microtome, in
order to estimate the average width, relative abundance and
proportion of the cortical vascular and pith regions. The s
sections, stained with Heidenhains haematoxylin and Bismarck
brown (Johansen, 1940), and dehydrated in ethanol series, will
be mounted in canada-balsam. The proportions of the various
stem and root components will be calculated by the method based
on the weights of paper cuttings of the camera lucida drawing
made on a tjiacing paper of uniform thickness (Ghouse v- Iqbal,
1975).
Internal structure of the leaf will be studied in
: 140 :
transverse sections. For cuticular studies, epidermal peels
will be obtained with the help of HNO^ using the method
evolved by Ghouse and Yunus (1972). The sections and epidermal
peels will be stained by the method of Johansen (1940), and
then dehydrated in ethanol series. Cells will be measured witn
the aid of ocular micrometer scale at suitable microscope magni
fications. The variation in the relative proportion of
different leaf tissues will be determined by the method devised
by Ghouse and Iqbal (1975). Counts of stomata and epidermal
cells will be made on a compound microscope at suitable magni
fications, Stomatal index (Sl) will be calculated by the Salis
bury's (1927) formula :
where S and E represent number of stomata and epidermal
cells, respectively, in a microscopic tield.
BIOCHEMICAL STUDIES :
Estimation of Chlorophyll and Carotenoid :
Since there is a close correlation between the amount of
chlorophyll and the rate of photosynthesis, the primary oro-
ductivity may be predicted on the basis of chlorophyll estima
tion (Billore^ Mall, 1975; Kumar et al. 1980).
: 141 :
The chlorophyll content of leaves of the selecteo crop
samples will be estimated according to Arnon (1949) using fresh
leaf samples. The chlorophyll of one gram fresh leavps will oe
extracted in 80% acetone in the forenoon. The fresh samples
of leaves in three replicates will be soaked in small amounts
of 80% acetone, crushed gently with mortar and pestle to extract
the chlorophyll and filtered with Whatman's filter paper No. 1.
The volume of the chlorophyll will be made 100 ml by adding 80%
acetone (80:20 acetone and distilled water). The absorption
at 645 nm and 663 nm and 480 nm of the pigments will be read on
spectrophotometer. The chlorophyll concentration in mg per grarr.
of fresh sample will be calculated using the following formulae
given by MaClachlan and Zalik (1963) and Daxbury and Yentsch
(1956) for chlorophyll and carotenoids, respectively.
r>ui / ^ . 12.3 D663 " 0.86 D645 ,, Chi a mg/g frw = d x 1000 x w ^ ^
r.,. . / .^,„ 19.3 D645 - 3.60 D645 ,, Chi b mg/g frw = d x 1000 x w ^ ^
r- X 4^ / ^ 7.6 D480 - 1.49 D510 ,, Carotenoids mg/g frw = — d x 1000 x w ^
where, D645 = Value of optical density at 645 absorption
spectra.
D663 = Value of optical density at 663 absorption
spectra.
: 142 :
D480 = Value of optical density at 480 absorption
spectra.
V = Volume of extract
W = Leaf portion weight
d = Length of light path.
Estimation of N, P. K :
Relative proportion of N, P and K in the leaves will be
estimated at different growth stages on dry weight basis.
Normal leaves from each plant will be taken randomly, dried in
an over for 24 hours and powdered.fine with 72 mesh screen.
The powder thus obtained and analysis which will be a accompli-yr
shed by the methods of Linder (1944; as follows :
Digestion of Sample :
100 mg dry powder of leaves will be taken in a 50 ml
Kjeldahl flask. Two ml of pure, H2S0^ (BDH) will be added
and the mixture be heated for about two hours to dissolve
the powder. This heating with the acid will turn the content
black. After cooling the flask for about 15 minutes, 0.5 ml
of chemically pure 30^ hydrogen peroxide will be added drop-
wise. The solution will be heated again for about 30 minutes,
until it turns light yellow in colour. Then it will be cooled,
: 143 :
With 3-4 drops of hydrogen peroxide , it will be reheated
for about 15 minutes to get a clean extract. Excess of hydro
gen peroxide will be avoided which would otherwise oxidise the
ammonia in the absence of organic matter. The peroxide digested
material will be transferred to 100 ml volumetric flask with
three or four washings with DDV/ and the volume be made upto mark
This will serve as a stock solution for the estimation of N,
P and K.
Estimation of Nitrogen :
According to Lindner (1944), a 10 ml aliquot of the
peroxide digested material will be transferred to a 50 ml
volumettic flask. Two ml of 2.5 N sodium hydroxide will be
added to neutralise the excess of the acid partially. To
prevent the turbidity, one ml of 10% sodium silicate will
be added to the flask and the volume be made up. In a 10 ml
graduated test tube, 5 ml of aliquot of this solution will
be taken and 0.5 ml of Nessler's reagent will be mixed
throughly. The final volume will be made up with DDW and
kept for about five minutes for the maximum colour development.
This solution will be taken in a colorlmetric tube and the
optical density measured at 525 nm. A olank will also be run
simultaneously during determination. A standard curve of known
: 144 :
dilution of ammonia sulphate solution will be plotted. Reading
of each sample will be compared with this callibration cruve.
Estimation of Phosphorus :
Phosphorus will be estimated by the method of Flske and
Subbarow (1925). In a 10 ml graduated tube, 5 ml of aliquot
will be taken and 1 ml of molybdate reagent will be added cax^-
fully, followed by 1, 2, 4 amino nepthol sulphonic acid (0.4
ml). This acid will turn the contents blue. The volume will
be made up and the solution be allowed to stand for about 5
minutes for the maximum colouration. Later it will oe trans
ferred to a calorimetric -cube and the optical aensity will be
read at 620 nm. A blank will be run for each determination.
A calibration curve will be prepared by using Known dil'jtions
of a standard monobasic potassium phosphate solution.
Estimation of Potassium :
Potassium will be estimated using a t Idme nnotcme^ter.
A blank will be rub side by side. The readings will De com
pared with a calibration curve plotted tor different oilutions
of a standard potassium sulphate solution.
Estimation of Sulphur :
The oven-dried samples of leaves will bo grounn anc pass^ *
: 145 :
through 72 mm mesh screen. 0.3 gram screened powder and 0.1
ml selanium dioxide (Se02) solutions will be digested using
10 ml HNOg and 1 ml HCl. The digested material will then be
filtered in 100 ml volumetric flask. The volume of the
digested material will be made up to 100 ml with 10 ml of 3%
glycerol, and added with 5 ml of 2% BaCl^ before using spectro-i
photometer. Optical density will be noted at 420 nm. Finally,
with the help of a standard curve of the potassium sulphate
solution, the actual sulphate concentration will be determined
and expressed in mg SO. in unit dry weight (Patterson, 1958).
Estimation of Cu. Fe. Mq. Mn. Ni. Pb and Zn :
72 mesh screened dried samples of leaves of the selected
species will be digested using HNO- and HCIO . The digested
material will then be filtered in 100 ml volumetric flask and
the volume made up to 100 ml with the double distilled water.
Cu, Fe, Mg, Mn, Ni, Pb, and Zn will be determined in each
solution on the atomic absorption spectrophotometer.
: 146 :
STATISTICAL ANALYSIS
The data collected on different parameters pertaining to
the foliar study carried out at the different study sites will
be statistically analysed as under to determine the degree of
authenticity of results.
Mean (X) :
The arithmetic mean, or simple or the so called average
value may be easily computed by taking the sum of a number of
values (X-j, X^, X^ and so on) and dividing by the
total number of values (N) involved, thus,
(XiH-X^^X3 X^) ^ - N
or X = jj
where X,, X^, X„ X = observations JL ^ o n
N = number of observations.
Standard Deviation (o or S,D,) :
Standard deviation is a measure of fluctuations in a sample
produced as a result of chance factor's of sampling from the
same population. It may be calculated by the following formula.
: 148 :
of the two samples viz. X and Y of two different populations
becomes important when it is to be judged whether or not
they differ significantly.
It will be computed as follows :
(S.D,)^ + (S.D^)^ S.E.D. =/ - ^
"l "2
where, S.D.-, = S.D. of one samples
S.D.^ = S.D. of other sample
n, = No. of observations in one samole
n^ = No. of observation in other sample
Coefficient of Variation (C.V.) :
This measures the relative magnitude of variation present
in observations relative to the magnitude of their arithamatic
mean. It is defined as the ratio of S.D. to arithmetic mean
expressed as a percentage.
eg. C.V. = ^'^' X 100 X
where, S.D. = S.D. of the concerned sample or population
X = Arithamatic mean.
Test of Significance :
The test of significance is a device to find out whether
: 149 :
or not an observed pair of means differs significantly from
each other, or this difference is just a result of chance
influence. It is a device, a criterion, to arive at a judge-
{ment and cotifidence about the validity of a result. The
following two tests will be applied for the purpose.
Student t-test :
It will be applied to test the significance of the
difference between the two sample means (if any), each sample
collected from the two study sites.
The following formula will be used to compute t-value
which will be compared with the table value of 't' at their
particular degrees of freedom. If calculated 't' value exceeds
the table value the difference between the two samples will De
treated as significant!, otherwise the difference will oe attri
butable to chance factor.
t =
or t =
Difference of two sample means Standard error of the difference
^1 ^2
(S.D.p2 ^ (S.D.2)'
y n 1 "2
wh ere, X, = Arithmatic mean of the one sample
X^ = Arithmatic mean of the other sample.
: 150
S.D., = S.D. of one sample
S.D.^ = S.D. of other sample
n-j = No. of observation of one sample
n^ = No. of observation of other sample
Degree of Freedom (D.F.) :
Degree of freedom, to be applied to the number of data
particularly in t-test will be calculated as follows:
D-F = Hj + n2 - 2
where, n, = No. of observations of one sample
n^ = No. of observations of other sample.
For its use in the least significant difference analysis
(L.S.D.)
DF = L(TxR) - IJ - [(R-i; + (T-1)]
where, T = Number of treatments
R = Number of observations.
Least Significance difference (L.S.D.) :
This test is applied to compare all pairs of means.
The following formula will be used to calculate L.S.D.
: 151 :
L.S.D. = , / M - J ^ X t-value
where, USE = Estimated variance of error,
r = No. of replicates.
^E ' (r-!f (t-1)
where, SSQE = Error sum of squires,
r = Number of replicates
t = Number of treatments
SSQE = SSQT - (SSQr - SSQt)
where SSQT = Total sum of squires.
SSQr = Sum of squires between replications
SSQt = Sum of Squares between treatment
SSQT = Sum of the squires of each value and substracted
from it correcting factor (C.F.)
r> n (Total)^ where, C.F. = . ^
ccnr - Sum of squares of replications _ p p No. of treatments-1
qcQf _ Sum of squares of t r ea tmen t ^ " No. of r e p l i c a t i o n s - 1 C.F.
Correlation Coefficient (r) :
This is a statistical measure which indicates both nature
and degree of relationship between two measurable characteristics,
say height (X-Cm) and yield (Y-gm). It will be computed as
: 152 :
follows:
NSXY - ( X) (SY) r =
/ [(NSX)^ - (^X)2j[(N£Y)2 - ( Y)2]
where, X = observations on height
Y = observation on yield
OR
S(X-XJ (Y-Y) r =
v^(x-x: 7 2 '< (X-X)'' (Y-Y)'
where, X = observation on one character
X = Arithmatic mean of all x observation
Y = Observation on other character
7 = Arithmatic mean of all Y observation.
A correlation coefficient may very from-l (perfect negative
correlation) to + 1 (Perfect Positive correlation). Any value
close to zero would denote a lack of correlation or a relatively
week correlation.
Coefficient of Determination (dj :
It is a derivative of correlation coefficient whpn express*
in percentage, it shows percent variation.
d = (r)2
or d = 100 (r) - expressed in percentage
; 153 :
where, d = coefficient of determined
r = correlation coefficient
Linear Regression ;
Correlation coefficient elucidates the nature and degree
of relationship between two characteristics. Due to such
correlation when variation in one variable brings in acompany-
ing changes in the other, it enables us to predict the value
of one variable from the knowledge of other.
The regression line best fitting the observation is given
by :
A
Y = a + bx
)Q = N^XY - (^X) (-g-X)
N X^ - ( X)^
a = 7 - bx
where, Y ^y-hat; indicates the predicated value of Y for a
given value of X, X, Y are observation of two va r i ab les , v i z . ,
height and yield a, b are the cons tan ts .
X, Y are ari thamatic means of a l l observat ions of the
respec t ive var iab les X and Y.
: 154
Processing and Interpretation of Data :
The data collected for quantitative characters will be
analysed by a computer running on a computer programme pre
pared for the above mentioned formulae and the results will
be interpreted with reference to climatic and geographical
conditions of the study sites.
REFERENCES
Abouguendia, Z.M. and Baschak, L.A. 1985. An Evaluation of the Sensitivity of Saskatchewan Forest Vegetation to Acid Precipitation, SRC Publication No. E. 902-6-E-85.
Ackerson, B.C., Havelka, U.D. and Boyle, M.G. 1984. CO^ enrichment effects on soybean physiology II, Effects of stage specific exposure. Crop. Sci. 24(6) : 1150-1154.
Adams, CM. 1982. The Response of Artemisia tilesii to Simulated Acid Precipitation. M.S. Thesis, Univ. of Tronto, Ontario.
Adomait, E.J,, Ensino, J. and Hofstra, G. 1987. A dose-response function for the impact of ozone on Ontario [Canada] grown white bean and on estimate of economic loss. Can. J. Plant Sci., 67(i) : 131-136.
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