Lec #5 Discuss the Nitrogen Cycle.pptx

7/30/2019 Lec #5 Discuss the Nitrogen Cycle.pptx

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Discuss the nitrogen cycle

Plant Physioloty

1/28/09Lec#4

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Distinguish between symbiotic and

asymbiotic with respect to nitrogen

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Plant forms a relationship with rhizobium

(nodules) in roots in symbiotic relationship.

Rhzobium fixes Nitrogen which becomes

available to plant

Asymbiotic

Azospirilum is in the rhizosphere (area of soil in

close association with the roots)

Found in sweet potato nitrogen is in the organic

form

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List two major symptom of

nitrogen deficiency in plants?

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Stunted growth

Yellowing of the older leaves (choroses)

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List effect of phosphorus in

plants

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Increase growth like N (but to lesser extent)

Part of genetic material

RNA, DNA, purine, pyrimadine

Part of energy transformation (ATP)_ Spurs early and rapid growth (starter fertilizer)

Improves water intake

Helps resist cold and disease

Improves quality of produce (grains and fruits)

Improves efficiency of N uptake

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What are the two general rule of

thumb for P as it relate to plant

growth?

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P more important for plants with floral parts

Broccoli

Cauliflour

P is taken up as a phospate ion

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How much P is in an acre of plow

layer and how much is available to

plants?

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800 1600 lbs

Only 4 lbs is available

The rest is tide up based on the pH

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At what pH is Phosphorus

available to plants?

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Between pH 6.5 and 7.0

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List the different species of P, and at

what pH they insoluble and

therefore not available to plants?

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Species of P

FePO4

AlPO4

CaPO4

Insoluble at pH

3.5 - 4.5

4.0 - 6.5

7 - 9

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List four important factors

associated with the mineralization of

phosphorus.

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1. Involves Microorganisms from organic matter

2. More rapid in virgin soil

3. Process favors high temp

1. Thermophilic (45-65 C)

2. Mesophilic (25 35 C) the optimum

4. Phosphorus uptake correlated withmineralization rate

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What is the impact of organisms

on P mineralization?

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Organisms produce enzymes

Phosphotases (help cleave phosphorus)

Organisms are pH dependent

Acid

Alkaline

Phosphotases / specific for organic

phosphotase key to attack

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List two important enzymes in soil

and how they are broken down.

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Inositol phosphate

Found when phytases are present

Broken down by organism

Phytases

Liberates P from phytin (or phytic acid)

Is broken down to penta, tetra, tri, di, and

monophosphates

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What is vernalization?


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Refers to the amount of chilling hours needed for budding to occur. Aftervernilization the plant is returned to normal temperature.

Many temperateplants have a vernalization requirement and must experience aperiod of low winter temperature to initiate or accelerate the flowering process,or, as the case with many fruit treespecies, to actually break dormancy, prior to

flowering. Many plant species, includingArabidopsis thaliana and winter cerealssuch as wheat, must go through a prolonged period of cold before floweringoccurs. This ensures that reproductive development and seed production occurs atthe optimum environmentally favorable time, normally following the passing ofwinter. The needed cold is often expressed in chill hours.

Following vernalization, plants have acquired the competence to flower, althoughthey may require additional seasonal cues or weeks of growth before they will

actually flower. One of the most important influences that temperature has on thefloral transition is the vernalization response. Some plant species do not flowerwithout vernalization. Many biennial species have a vernalization period, whichcan vary in period and temperature. Typical vernalization temperatures arebetween 5 and 10 degrees Celsius (40 and 50 degrees Fahrenheit).
http://en.wikipedia.org/wiki/Temperatehttp://en.wikipedia.org/wiki/Plantshttp://en.wikipedia.org/wiki/Flowerhttp://en.wikipedia.org/wiki/Fruit_treehttp://en.wikipedia.org/wiki/Specieshttp://en.wikipedia.org/wiki/Flowerhttp://en.wikipedia.org/wiki/Fruit_treehttp://en.wikipedia.org/wiki/Specieshttp://en.wikipedia.org/wiki/Arabidopsis_thalianahttp://en.wikipedia.org/wiki/Arabidopsis_thalianahttp://en.wikipedia.org/wiki/Cerealshttp://en.wikipedia.org/wiki/Arabidopsis_thalianahttp://en.wikipedia.org/wiki/Cerealshttp://en.wikipedia.org/wiki/Wheathttp://en.wikipedia.org/wiki/Chilling_requirementhttp://en.wikipedia.org/wiki/Chilling_requirementhttp://en.wikipedia.org/wiki/Biennial_planthttp://en.wikipedia.org/wiki/Biennial_planthttp://en.wikipedia.org/wiki/Biennial_planthttp://en.wikipedia.org/wiki/Chilling_requirementhttp://en.wikipedia.org/wiki/Wheathttp://en.wikipedia.org/wiki/Cerealshttp://en.wikipedia.org/wiki/Arabidopsis_thalianahttp://en.wikipedia.org/wiki/Specieshttp://en.wikipedia.org/wiki/Fruit_treehttp://en.wikipedia.org/wiki/Flowerhttp://en.wikipedia.org/wiki/Plantshttp://en.wikipedia.org/wiki/Temperate


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Distinguish between

translocation and mobilization


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Translocation refers to the uptake of nutrients

by plant and moving them to tissues.

Mobilization refers to the movement of

water and nutrients in higher plants.


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Name two conducting tissues in

plant and their function.


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Xylem- involved in theuptake of water & somenutrients (via mass flow). It is the woody part of the

plant

Covered by a thin layer(cambium- dividing)

Phloem transportsphotosynthates for

carbohydrates from leavesto lower part of plants(roots) The outer part of the plant is

dead phloem (bark)
http://upload.wikimedia.org/wikipedia/commons/e/ed/Stem-cross-section2.jpg


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Consequences of Phosphorus

deficiency in plants


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Stunting but plant

remain green

Purplish tint on leaves

(lower and older leaves) Delayed crop maturity

Poor root system

(especially in carrots)

Purplish tint

on leaves

Poor root system

http://images.google.com/imgres?imgurl=http://www.steve.gb.com/images/science/phosphorus_deficiency.png&imgrefurl=http://www.steve.gb.com/science/plant_mineral

_nutrition.html&usg=__yhJBnXzeX4g8VbCgi6COn2m6Aek=&h=383&w=244&sz=12&hl=en&start=2&um=1&tbnid=vMddcOipE-wb8M:&tbnh=123&tbnw=78&prev=/images%3Fq%3Dplants%2Bwith%2Bphosphorus%2Bdeficeincy%26um%3D1%26hl%3Den%26safe%3Dactive%26rlz%3D1T4RNWE

_enUS315US315%26sa%3DN&safe=on


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List 5 reason potassium is

important to plants.


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K is not part of any organic plant cmpd

Role in enzyme activator in protein

Starch cellulose and lignin formation

Regulates stomata opening (play role in gas exchange)

Instrumental in moving (Pn) sugars Impo in fruit and vege (and root crop)

Important in development and ripening of fruits and root(tuber) crops

After six weeks of planting, give a shot of K, helps in root production Lends integrity to plant structure (due to role in activating

enzymes involved in lignin.


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Describe the mobility of K and P

in soils


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K moves readily in soils

P does not move readily in soils, they are

immobile.


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What is marginal chlorosis?


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Similar to chlorine toxicity.

Due to salt damage and low moisture

This is why after snow fall plant near

highway/roads are

Symptoms of severe K deficiency in a soybean

leaf (left) compared to a leaf from a K-sufficient

plant (right).

Soybean plants exhibiting K-deficiency symptoms

only on lower leaves. This indicates that K is

mobile in soybean and is preferentially transported

to young tissues when deficiencies exist.
http://www.agry.purdue.edu/images/kteam/big/kteam7.jpg


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What is the role of Ca++ in plants

(list at least 3)?


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Mainly build cell walls

Iie, Calcium pectate= cement cell walls together

and responsible for crunchiness in apples.

Actively dividing cells need more

Play role in protein and carbohydrate

formation

Role in seed formation

Relatively immobile in plants


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List 3 consequences of Ca++

deficiency.


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In new growth causes

tip dieback

In fruits blossom-end

rot (BER) Water cone in apples

( collapsing of fruit cell

walls)

Empty pods (in

peanuts)

Browning and die back

from the tip of a plant.


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List the steps in translocation


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1. Centripetal

1. Water movement from outside in

2. Toward xylem vessels of the central cylinder

2. Vertical transport

1. Roots to leaves

3. Release of water as gaseous molecules at

the plant/atmosphere interfaces


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In a diagram show how water

transport occurs in the roots.


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leaf

petiole

stem

xylem

transpiration

Caspirian strip

cortexendodermis

epidermis

water

Free

space

2 Water transport pathways in the higher plant of a young root from

epidermis to the xylem. In young roots plants uses both apoplastic and

symplastic transport. In older plants, the plasmodesmata is developed and

the casparian strip is more resistant. Water transport is via the symplastic

pathway only.

Soil

Present high

resistance to water and

solute transport. As

plant gets older, it gets

more resistant

Separates cortex from central cylinderGenerally characterized by a suberized

layer


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Distinguish between symplastic and

apoplastic transport pathways.


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Apoplastic Seen in young root only

Characterixed withplasmodesmata

Transport is through free space

in root tissue

Symplastic

Most important

Transports nutrients also (Ca++)

Also Seen in young roots Water transport is through the

cytoplasm of root cells

Only on older roots
http://en.wikipedia.org/wiki/File:Apoplast_and_symplast_pathways.GIF

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Lec #5 Discuss the Nitrogen Cycle.pptx

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