© ICSE StudyMate – icsestudymate.com
Instagram: @icsestudymate | Telegram: t.me/icsestudymatetalks | Youtube- ICSE StudyMate
Mail : [email protected]
Copyright © ICSE StudyMate. Any unauthorized use and/or
duplication of this material without express and written permission
from this site’s author and/or owner is strictly prohibited. Excerpts
and links may be used, provided that full and clear credit is given
to ICSE StudyMate with appropriate and specific direction to the
original content. Infringement of the copyright may lead to charges
under the Indian Copyright Act.
1
© ICSE StudyMate – icsestudymate.com
Instagram: @icsestudymate | Telegram: t.me/icsestudymatetalks | Youtube- ICSE StudyMate
Mail : [email protected]
TRANSPIRATION
Basic Concepts :
*) Transpiration : Transpiration is the loss of water in the form of water
vapours from the leaves and other aerial parts of the plant.
*) Measurement of transpiration :
Potometer Method: Potometer is a device which is used to measure
the rate of transpiration
Ganong’s potometer :
Precautions in the use of potometer :
i)The potometer should be water tight.
ii)The twig should be cut obliquely ( to allow larger surface for the water
intake) and under water to avoid suction of an air bubble into the twig
which will stop the absorption of water into the xylem.
Limitations in the use of potometer :
i) Introducing the sir bubble is not very easy.
ii) The twig may die.
iii)Any changes in the outside air temperature may affect the position of
the air bubble in the capillary tube.
2
© ICSE StudyMate – icsestudymate.com
Instagram: @icsestudymate | Telegram: t.me/icsestudymatetalks | Youtube- ICSE StudyMate
Mail : [email protected]
TYPES OF TRANSPIRATION
StomatalTranspiration
CuticularTranspiration
LenticularTranspiration
i) Stomatal Transpiration : Occurs through stomata Which are minute
openings in the epidermal layer of leaves.
ii) Cuticular Transpiration : Occurs through cuticle Which is a waxy layer
secreted by the epidermis on the two surfaces of the leaf. The The
greater the thickness of the cuticle, the lesser is the transpiration.
iii) Lenticular Transpiration : Occurs through Lenticels which are special
openings that develop on the barks of older stems in the place of
stomata. Lenticels never close. They remain open all the time.
The amount of transpiration from lenticels is certainly more than the
cuticular transpiration, but very much less than the stomatal transpiration.
i.e,
Stomatal > Lenticular > Cuticular
3
© ICSE StudyMate – icsestudymate.com
Instagram: @icsestudymate | Telegram: t.me/icsestudymatetalks | Youtube- ICSE StudyMate
Mail : [email protected]
*) Factors that affect Transpiration :
A. EXTERNAL FACTORS :
1. Intensity of sunlight : Rate of transpiration increases with the increase
in the intensity of sunlight.
2. Temperature : Rate of Transpiration increase with temperature.
3. Velocity of wind : Transpiration increases with the velocity of wind.
4. Humidity : Transpiration is reduced if the air outside is humid.
5. Carbon Dioxide : Increase in CO2 results in less Transpiration.
6. Atomoshperic Pressure : Increase in Atmospheric pressure results in less Transpiration.
B. INTERNAL FACTORS :
1. Water content of the leaves : If there is shortage of water content in
the plant the leaves will wilt and transpiration is reduced due to
closure of stomata.
4
© ICSE StudyMate – icsestudymate.com
Instagram: @icsestudymate | Telegram: t.me/icsestudymatetalks | Youtube- ICSE StudyMate
Mail : [email protected]
*) Adaptations in plants to reduce excessive Transpiration.:
1) Sunken Stomata/ covered with hairs.
2)Fewer stomata
3)Narrow leaves to reduce surface area.
4)Reduced exposed surface , rolled , folded leaves.
5)Loss of leaves
6)Thick cuticle formation.
*) Significance of Transpiration :
1)Cooling effect
2)Creating suction force to draw water.
3)Distribution of water and minerals.
Transpiration Increases the moisture in the atmosphere and brings rain.
*) Guttation – Guttation is the loss of water as droplets along the margin
of leaves trough hydathodes in some plants Like banana.
*) Bleeding – Bleeding is the direct flowing out of plant sap from any cut
surfaces in case of injury.
5
© ICSE StudyMate – icsestudymate.com
Instagram: @icsestudymate | Telegram: t.me/icsestudymatetalks | Youtube- ICSE StudyMate
Mail : [email protected]
Give Reasons :
1. Leaves of the plants wilt during the hot day.
Ans> When the surrounding temperature is high , the rate of transpiration
increases; But the rate of absorption of water & minerals from the root
by the plants remain the same as a result, The rate of transpiration
exceeds the rate of Absorption which creates a scarcity of water within
the body of plants. Hence Plants generally wilt during hot day.
2. Stomata are more numerous on the lower surface of dorsiventral leaf.
Ans> All surfaces of the leaf have some amount of stomata for regulating
gas exchange for photosynthesis. However, The lower epidermis has
more stomata because it is more often in the shade and so it is cooler,
which means evaporation won’t take as much.
3. Leaves sometimes drip water at night.
Ans> The stomata remains closed during night , so no stomatal
Transpiration occurs during Night. Though Lenticular Transpiration
occurs During night but it’s not enough to release the extra water
intaked by the plant, So this extra water escapes from small pores
known as hydathodes. Water is released in the form of droplets. Thus,
leaves Sometimes drip water at night.
4. During The day Transpiration and Photosynthesis are interlinked.
Ans> In the daytime, Stomata are open to facilate the inward diffusion of
carbon dioxide for photosynthesis and water vapours are also lost to
the outside during transpiration. So, Stomatal Transpiration can take
place and Carbon dioxide can also enter the green leaf to enable
photosynthesis to take place. Thus, Transpiration And Photosynthesis
are interlinked.
6
© ICSE StudyMate – icsestudymate.com
Instagram: @icsestudymate | Telegram: t.me/icsestudymatetalks | Youtube- ICSE StudyMate
Mail : [email protected]
5. While setting up the potometer, The leafy shoot should be cut under
water.
Ans> While setting up the potometer, the leafy shoot must be cut under
water because if air gets into the xylem vessels of the plants, it can
form air locks which will prevent the plant taking up water.
6. Forests tend to bring more rainfall.
Ans> Transpiration helps in bringing more rain because more the number
of trees in a particular locality implies more humidity which on
condensation the upper layer of atmosphere precipitates down as
rain.
Name the following.:
1. Openings on the stem through which transpiration occurs. – Lenticels
2. The process by which the intact plant loses water in the form of
droplets- Guttation
3. An instrument used to find the rate of transpiration – Potometer
4. A plant in which the stomata are sunken. – Nerium
5. The apparatus to record the rate of transpiration in a cut shoot. –
Ganong’s Potometer.
6. Any two parts of a leaf which allows transpiration. – Stomata, cuticle
7. The structure in a leaf that allows guttation. – Hydathodes
8. Loss of water as droplets from the margin of certain leaves. –
Exudation/ Guttation.
7
© ICSE StudyMate – icsestudymate.com
Instagram: @icsestudymate | Telegram: t.me/icsestudymatetalks | Youtube- ICSE StudyMate
Mail : [email protected]
Review questions.
1. What do you mean by transpiration?
2. Define Stomatal & cuticular transpiration.
3. Write a short note on lenticular transpiration.
4. Write the factors and conditions affecting transpiration.
5. What are the adaptations In the plants to reduce transpiration?
6. What is potometer? Write its limitations.
7. Write any four Significance of transpiration.
8. Write any two disadvantages of transpiration.
9. What is the transpiration stream?
10. Distinguish between transpiration & guttattion.
11. Given below is the diagram of an experimental set-up to study the
process of transpiration in plants. Study the same and then answer
the questions that follow:
a) What is the colour of dry cobalt chloride paper?
b) Is the experimental leaf a monocot or a dicot? Give a reason to
support your answer.
c) Why are the glass slides placed over the dry cobalt chloride paper?
d) After about Half an hour what change, if any, would you expect to find
in the cobalt chloride paper placed on the dorsal and ventral sides of
the leaf? Give a reason to support your answer.
8
© ICSE StudyMate – icsestudymate.com
Instagram: @icsestudymate | Telegram: t.me/icsestudymatetalks | Youtube- ICSE StudyMate
Mail : [email protected]
Answers:
1. Transpiration is the loss of water in the form of water vapours from
the leaves and other aerial parts of the plant.
2. Stomatal transpiration : The epidermis of the leaf has numerous pores
called stomata. These pores remain open during the day so that CO2
of the air can diffuse in an enable the plant to prepare food by
photosynthesis. Simultaneously the excess water in the form of Water
vapour is screted out through Stomata. This process is known as
Stomatal Transpiration.
Cuticular Transpiration : The epidermis of the leaves secrete a thin
layer of waxy, known as cuticle. The cuticle is not very permitable to
water However, Its molecules absorb water from the epidermal cells
by imbibition. The imbibed water is slowly Lost to the atmosphere.
This is known as cuticular Transpiration.
3. Stems of the woody plants have openings on their surface called
lenticels. Transpiration continues throughout day and night through
this lenticels since they are always open and the Water vapour easily
escapes through the loose mass of cell of each lenticel. This is known
as lenticular transpiration.
4. Intensity of sunlight : Rate of transpiration increases with the
increase in the intensity of sunlight.
Temperature : Rate of Transpiration increase with temperature.
Velocity of wind : Transpiration increases with the velocity of wind.
Humidity : Transpiration is reduced if the air outside is humid.
Carbon Dioxide : Increase in CO2 results in less Transpiration.
Atomoshperic Pressure : Increase in Atmospheric pressure results in less
Transpiration.
9
© ICSE StudyMate – icsestudymate.com
Instagram: @icsestudymate | Telegram: t.me/icsestudymatetalks | Youtube- ICSE StudyMate
Mail : [email protected]
5. i) Sunken Stomata/ covered with hairs.
ii)Fewer stomata
iii)Narrow leaves to reduce surface area.
iv)Reduced exposed surface , rolled , folded leaves.
v)Loss of leaves
vi)Thick cuticle formation.
6. Potometer Method: Potometer is a device which is used to measure the
rate of transpiration
Limitations in the use of potometer :
i) Introducing the sir bubble is not very easy.
ii) The twig may die.
iii)Any changes in the outside air temperature may affect the position of
the air bubble in the capillary tube.
7. i)Removal of excess water from the plants
ii) Cools the plants
iii)Cools the enviroment.
iv)Prevents the plant from drying up.
8. Two disadvantages of transpiration are:
i) Plants often wilt and die when excessive transpiration takes
place,that is , when the rate of transpiration through leaves exceeds
absorption of water through the roots.
ii) Since most of the water absorbed is lost by transpiration, plants have
to work more to compensate the loss.
9. Tanspiration stream is the path of movement of mineral sap through the
vessels and tracheids of xylem tissue, Due to transpiration.
10
© ICSE StudyMate – icsestudymate.com
Instagram: @icsestudymate | Telegram: t.me/icsestudymatetalks | Youtube- ICSE StudyMate
Mail : [email protected]
10.
Transpiration Guttation
i)Water is lost in the form of
vapour.
ii)It cools the plant body.
iii)It occurs in the presence of
sunlight.
iv)It occurs during dry
conditions.
i)Water is lost in the form of
water droplets.
ii)It has no such effect on the
plant.
iii)It generally occurs at night.
iv)It occurs in humid conditions.
11. a) The colour of dry cobalt chloride paper is Blue.b) The experimental leaf is a dicot leaf because the experimental leaf
have sub-veins.c) The glass slides are placed over the dry cobalt chloride paper
because to block the Atmospheric water vapour to come in contact with the cobalt chloride paper. If the Cobalt chloride paper comes in contact with Atmospheric water vapour then the reading would be inaccurate.
d) After half an hour we will observe that the cobalt chloride paper which is placed on the dorsal side of the leaf will be coloured more deep pink than that of the Ventral side because there are more stomata in the dorsal side than there are in ventral side so more transpiration occurs in dorsal side than ventral side thus the cobalt chlorde paper turns pink more faster than of ventral side.
Website- icsestudymate.com
Instagram- @icsestudymate
Telegram- ICSE StudyMate
Email- ICSE StudyMate
YouTube- ICSE StudyMate
© ICSE StudyMate – icsestudymate.com
Instagram: @icsestudymate | Telegram: t.me/icsestudymatetalks | Youtube- ICSE StudyMate
Mail : [email protected]
Aditi AgrawalICSE student, Batch of 2018
If you want to contact me personally,
Email- [email protected]
Instagram- @icsestudymate
© ICSE StudyMate – icsestudymate.com
Instagram: @icsestudymate | Telegram: t.me/icsestudymatetalks | Youtube- ICSE StudyMate
Mail : [email protected]
Hey there!
Firstly, we are glad you are here with us at
ICSE StudyMate. I founded ICSE
StudyMate in 2018 with the sole purpose of
helping students. I was really lucky to find
many more people who had the same vision
and now we all work together towards this
common goal. Thank you for believing in us
and we promise to help you at each step in
this journey of yours. Good luck with your
preparation and remember ICSE, it’s easy!
© ICSE StudyMate – icsestudymate.com
Instagram: @icsestudymate | Telegram: t.me/icsestudymatetalks | Youtube- ICSE StudyMate
Mail : [email protected]
Hey Studymates,
Hope you all are doing well! My name is
Debanjan Bhadra. I'm currently in 11th Grade
with Science as my stream. I aspire to be
Software developer. I scored an aggregate of
92% in my ICSE examination and I'm really
lucky to share with you whatever I've learnt in
my journey. I am also very thankful to ICSE
Studymate for giving me a platform where I got
a chance to showcase my knowledge and share
it to the world, Which i am sure people will get
benefited. This Education page really helped me
so much in my academics and mainly for my
ICSE exams, and i am sure all those students
who are aiming for excellent performance in
their ICSE will really be Helpful. Good luck to all
my juniors with your preparation! Stay Safe! :)Debanjan Bhadra
ICSE student, Batch of 2020
If you want to contact me personally,
Instagram- @dean_bhadra
Will glad to help you.
For more check out Testimonials
© ICSE StudyMate – icsestudymate.com
Instagram: @icsestudymate | Telegram: t.me/icsestudymatetalks | Youtube- ICSE StudyMate
Mail : [email protected]