TOPIC: PHYSIOLOGICAL CHANGES IN PLANTS DURING MOISTURE STRESS CONDITION

PRESENTED BY ZUBY GOHAR ANSARI

TAM/14/26

INTRODUCTION WHAT DO YOU MEAN BY

PHYSIOLOGICAL CHANGES:

EFFECTS OF WATER DEFICITS ON PHYSIOLOGICAL, MORPHOLOGICAL AND BIOLOGICAL PROCESSES

1. Water deficit at cellular leveli. Cell Division: It is less affected as compared to

cell elongation.ii. Ex. Radish leaves DNA content reduced to 40%

of control leaves at W.P. of -2 bars and to 20% at -8 bar.

iii. Cell Enlargement: Reduction in T.P. causes in cell enlargement, which in turn decreases root and shoot elongation.

iv. Also interferes with stomatal opening.

2. Leaf Expansion : In maize, rate of leaf enlargement is greatest when leaf water potential is in the range -1.5 to -2.5 bars.

As leaf water potential falls to -9 to -10 bars, leaf elongation vertically ceases, photosy. Was slightly impaired.

3. Turgor: Lag in absorption behind transpiration → loss in turgor → due to rise in transpiration→ due to increase in atmospheric dryness with onset of drought.

4. Plant structures: Leaf area, cell size & intercellular volume are

usually decreased. Cutinization, hairiness, stomatal frequency and

thickness of both palisade layers increased.

5. Root development: It is affected by soil water potential in a number of ways

In G’nut & wheat wt. of root decreased but number of root is same approx.

Roots grow towards water in the soil.

6. Photosynthesis: Water stress can reduced photosy.by

Reduction in leaf area Closure of stomata Reduction in activity of dehydrated

protoplasmic machinery Reduce photosyn. surface

Reduce the production of dry matter The leaf water potential at which stomata

close varies withA. Position of the leafB. Leaf ageC. Growth conditionD. Rate of stress

7. Respiration: It increases in early stage afterwards decreases as it is severe.

Severe dehydration of tissues caused a burst of respiration in some species results of hydrolysis of starch to sugars

In general reduction in photosynthesis, commences W.P. commences to zero.

It decline more or less turgor pressure to a value of zero.

8.Distribution of assimilates: Distribution pathway is highly resistant to water stress.

Velocity of assimilatory movement was influenced by water stress as low as -30 bars in wheat.

Effect of water deficit distribution of assimilates to various plant organs will depends on

I. Stage & development of plantsII. Pre-history of stressIII. Degree of stressIV. Degree of sensitivity to stress of organs

9.Photorespiration: It is unaffected by short term stress in certain conditions but substrate for photorespiration depleted.

10.Protoplasmic effects of water deficit: Removal of water surrounding protein molecules may cause changes in configuration affecting permeability, hydration, viscosity & enzyme activity.

11. Carbohydrate metabolism: In cotton as a result of stress, the sugar content increases & starch content decreases.

By contrast, in stems, the conc. Of both sugars and starch increases indicating reduced water supply not only affects photosynthesis but also the ability of plants to utilize the products of photosyn.is still more impaired.

12. Enzyme activity: In maize increase in water stress cause nitrate reductase activity decline at much greater rate than peroxidase activity.

Levels of enzymes involving hydrolysis and degradation usually either remains same or increase.

13. Nitrogen metabolism: Hydrolysis of proteins occur in wilted plants is accompanied by increased amino acids.

Synthesis of RNA & proteins are decreased in sugar beet before visible wilting occurs.

14. Nucleic acid: its synthesis is unaffected by moderate stress in older leaves, but Rnase activity increases which degrade RNA.

Reduced growth of stressed seedling due to alternation of nucleotide composition Of the RNA.

15. Ageing: It produces changes in the course of protein synthesis and water stress greatly accelerate the change normally associated with senescence.

16. Growth regulators: A. ABA: In water stress plants , ABA

synthesized and released from mesophyll to chloroplast and travels to guard cells where it

a. Inhibit K+ uptake b. Inhibit H+ releasec. Promote leakage of malate from guard cells. These effects cause guard cells to lose

turgor. Loss of turgor decreases stomatal aperture.

B. Cytokinins: In stressed sunflower plants, cytokinin content in root exudates was reduced.

In detached lettuce leaves, water stress had the effects of decreasing cytokinin as ABA increased.

C. Gibberellins: GA declined in tomato shoot, root following stress applied by flooding roots.

D. Auxins: IAA in sorghum leaves decreased as a result of water stress.

Water stress can directly affect the action of IAA in shoots.

E. Ethylene: In cotton plants, water stress induced abscission of leaves that is promoted by plants.

Water stress in cotton, bean plants, ethylene level are elevated rapidly in both leaves and petioles.

17.Reproductive and grain development:

A. flowering: Moisture regimes during this period largely determines the no. of fruits which will be produced.

B. Fruit enlargement: Severe stress during this period results in small or shriveled grains.

C. Ripening: Water stress has no effect on yield component but may effect length of ripening period.

18. Crop yield: Effect of water stress on yield depends on stage at which it occurs.

At early stage, no. of primordial branches may be reduced.

Drastic effect of stress was observed at flowering stage.

EFFECTS ON CEREALSOn floral initiation, anthesis

(wheat& rice).At ripening stage (reduc. in test

wt.).Plant height, leaf area.Leaf rolling, drying, premature

death of leaf.Reduc. in photosyn. & dry matter

production.

EFFECTS ON PULSES & FRUIT CROPS• Flower abortion .• Stress during pod filling reduces test

weight.

• In fruits, shedding of fruits. Ex. June drop of apples & citrus.

• In some cases, drought prevails causes premature flowering which results in reduced yield, size of pods, seeds & fruits.

MOST SENSITIVE STAGES OF MAJOR CROPS 1. Rice: panicle initiation, flag leaf & milky 2. Sorghum: booting & flowering 3. Maize: tasseling & silking 4. Groundnut: peg penetration & pod

development 5. Sunflower: head formation and early grain

forming 6. Pearl millet: booting & flowering 7. Finger millet: flowering 8. Soybean: flowering & pod filling 9. Cotton : square formation & boll development 10. Black & Green gram: flow. & early pod

develop.

EFFECTS OF STRESS IN MAIZETasseling and silking stage ( most

harmful) , grain filling reduc. yield drastically than at vegetative stage.

Pollen develop. slower leads to reduc. fertility → reduc. in grain no. wt. per ear.

During anthesis shorten duration of grain filling by causing premature desiccation of endosperm & by limiting embryo volume.

EFFECT OF WATER STRESS IN SUNFLOWERDrought tolerant cropDeeper root system → due to stress

at veg. stageYield and oil content decreases Interesting fact 1. under normal cond. Oil content

and seed is high than seed protein content.

2. In mild stress cond. Seed protein content high in hybrids than that of oil content.

EFFECTS OF WATER IN SOYBEAN Leaf expansion rate reduced Leaf flipping movement seen Water stress causes early flowering &

reproductive growth Leaf clampingEffect of water stress in groundnut:

Fairly drought tolerant Low rainfall, prolonged dry spell decrease its yield Photosyn. , carbohy. ,chlorophyll , enzymatic

activity ,internodal length , pod & kernel development reduced.

EFFECTS OF WATER STRESS IN COTTONo Affect both production & distribution of

carbohydrates.o Reduction of leaf area o Mummified dry bolls ( younger bolls)o Older bolls size reducedo Stress during peak flowering and early pod

develop. reduced yield

GROWTH STAGES

REDUCTION IN YIELD WITH ONE

DAY OF STRESS(Kg lint/ha)

Squaring 9.2

Peak flowering 18.8

Late flowering 16.1

Boll maturation 3.6

Hearn and Constable 1984

METHODS FOR MITIGATE ADVERSE CONDITIONS OF WATER STRESS IN CROPS 1. RICE: a) Seed hardening KCl 1% with CCC 50 ppm &

foliar spray of 1000ppm CCC → increased grain yield up to 5723 kg/ha

b) Foliar spray of murate of potash 2% at flower initiation → 400 kg/ha

c) Foliar spray of 0.3 ppm of brassinolide at panicle initiation and flowering → 605t/ha

2. SORGHUM : kaolin 3% foliar spray → 10%

3.RAGI: Seeds treated with CCC 5 ppm → 12%

4. BAJRA: Combined spray of 0.5% ZnSO4 & 0.5% CuSO4 together with boric acid 0.2% → 16.8%

Soaking Bajra seed with 2% KCl or NaCl for 16 hrs → 329 kg/ha

5.SOYBEAN: Kaolin 3% or liquid paraffin at 1% as foliar spray → 10%

Foliar spray of salicylic acid 100 mg/lit on 30 & 45 DAS → 16%

6.BLACKGRAM: Foliar spray of KCl at 0.5% during flowering → 100 kg/ha

7.SESAMUM: KCl 0.5% spray at flowering & capsule maturity phase → 1204 kg/ha

8.GROUNDNUT: Foliar spray of KCl 0.5% → 10%

9. COTTON: Foliar spray of kaolin 3% & liquid paraffin 1% spray → 27.4%

BENEFICIAL EFFECTS OF WATER STRESS

1.Moderate water stress improved the quality of Apples, Pears, Peaches and Plums.

2.Water stress increases the alkaloid content in datura.

3.Water stress increases the percentage of oil in soybean but decreases the yield of oil per acre.

4.Protein content of wheat increased by water stress during maturation.

5. Although water stress decreases total vegetative growth , it generally increases the rubber content in rubber plants.

WATER STRESS IN RELATION TO DISEASES AND INSECT RESISTANCE 1. Development of bark cankers is

usually correlated with decreased water content of the bark.

2.The incidence of blossom end rot of tomato fruits is said to be higher on plants subjected to severe water stress.

3. Trees with low water stress have high oleoresin exudation pressures, which seems to be unfavorable to the establishment of beetles.

CASE STUDIES

RHIZOBIAL INTERACTION WITH WHEAT UNDER WATER STRESS(GROWTH AND NITROGEN ASSIMILATION UNDER STRESS AND NORMAL CONDITION)

TREATMENTS

WATER STRESS

NORMAL

WATER CONDITION

YIELD (g/pod) YIELD (g/pod)GRAIN STRAW BIOLOG

ICALGRAIN STRAW BIOLOGICAL

UNINOCULATED

2.4 5.6 8.0 8.1 10.1 18.2

Os 4 2.7 5.6 8.3 8.6 12.4 21.0Ew24 3.6 5.8 9.4 11.1 14.0 25.111a 5.1 8.3 13.4 14.4 17.8 32.2

17bt 5.0 8.4 13.4 12.1 14.8 26.9M 10 4.8 9.1 13.9 11.3 12.3 23.6Os 2 6.3 8.4 14.7 7.2 13.2 20.4SEm± 0.2 0.4 0.3 0.5 0.7 0.3C.D.(0.05)

0.7 1.2 0.7 23.9 25.1 6.8

TREATMENTS

WATER STRESS NORMAL

WATER CONDITION

NITROGEN

(mg/pot) NITROGEN

(mg/pot)

GRAIN STRAW TOTAL GRAIN STRAW TOTALUNINOCULATED

62.0 59.0 121.0 182.0 72.0 254.0

Os 4 71.0 23.0 94.0 202.0 69.0 271.0Ew24 93.0 40.0 133.0 250.0 107.0 357.011a 124.0 51.0 175.0 252.0 85.0 337.017bt 150.0 87.0 237.0 263.0 96.0 359.0M 10 132.0 81.0 213.0 260.0 71.0 331.0Os 2 162.0 53.0 216.0 207.0 73.0 280.0SEm± 6.4 5.8 4.4 11.9 4.0 8.7C.D.(0.05)

18.5 16.8 12.7 25.8 24.6 13.7

Indian journal of plant phy.(april-june,1997) Sangeeta paul IARI newdelhi

LEAF EXPANSION IN BRASSICA SPECIES IN RESPONSE TO WATER STRESS (LEAF WATER POTENTIAL,R.W.C. , & SOLUTE POTENTIAL AT ZERO TURGOR IN BRASSICA SPECIES)

SPS./STRESS TREATMENT

LEAF W.P.(MPa)

R.W.C. S.P AT ZERO T.P.(MPa)

BEFORE STRESS PERIODB.juncea -0.45 0.81 -1.01B.napus -0.64 0.94 -1.32

END OF STRESS PERIODB.J Control -0.89 0.78 -1.14Stressed -1.33 0.74 -1.49

B.N Control -0.98 0.81 -1.24Stressed -1.58 0.69 -1.57AFTER REWATERING, TWENTY FOUR HOURS

B.J Control -0.85 0.76 -1.20Stressed -1.14 0.72 -1.38

B.N Control -0.90 0.81 -1.27Stressed -1.24 0.74 -1.50

EFFECT OF WATER& RECOVERY ON LEAF AREA (CM SQUARE/PLANT)

SPECIES STRESS PERIOD RECOVERY PERIOD

CONTROL STRESSED CONTROL STRESSED

B. juncea 135.0 106.8 149.4 125.2

B.napus 81.5 70.2 102.5 81.0

A.KUMAR & J.ELSTON

EFFECT OF WATER STRESS ON PHOTOSYNTHESIS AND WATER RELATIONS OF WHEAT VARIETIES (EFFECT OF WATER STRESS ON STOMATAL RESISTANCE & PHOTOSYNTHESISOF WHEAT VARIETIES)

VARIETY

TREATMENT

STOMATAL RESISTANC

E

(S/cm invers

e)

NET PHOTOSYN.

(P net)

(µl CO2

per m sq. sec

inverse

T.S. A.S. S.D.S. T.S. A.S. S.D.S.

C-306 Control 1.32 2.97 2.63 10.86 15.54 6.18

Drought

2.17 4.34 8.16 9.74 11.66 4.64

Reirrigated

1.40 3.10 3.08 11.30 14.02 6.00

Kalyansona

Control 1.14 2.58 2.91 13.56 16.58 8.02

Drought

1.33 3.2 8.53 5.70 7.84 3.14

Reirrigated

1.18 2.87 3.16 13.62 13.62 8.20D.C.Uprety and G.S. Sirohi, IARI New Delhi

PHYSIOLOGICAL AND BIOCHEMICAL CHANGES IN CLUSTER BEAN ( CYAMOPSIS TETRAGONOLOBA L.) GENOTYPES UNDER WATER STRESS

VARIETIES Stem

CONTROL

Leaf Seed

HG-75 1.841 1.951 1.738 2.271 0.675 0.573

IC-11521 1.894 1.500 2.044 1.379 0.864 0.483

DURGAJAY

2.357 2.820 2.234 2.987 1.097 1.172

FS-277 1.466 1.763 1.594 2.034 0.927 0.643

19-1-55 2.079 1.637 1.445 1.623 0.902 0.920

CONTROL STRESS CONTROL STRESSSTRESS

EFFECT OF WATER STRESS ON DRY WEIGHT OF STEM,LEAF,SEEDS IN FIVE GUAR VAR.AT HARVEST.(CLUSTER BEAN) (g/plant)

SOURCE: INDIAN JOURNAL OF PLANT PHYSIOLOGY M.S Kuhad and I.S Sheoran

VARIETIES

PROLINE

CONTROL

STRESS

SOLUBLE SUGARS

CONTROL

STRESS STARCH

CONTROL

STRESS

HG-75 2.371 12.180 7.702 8.282 17.55 6.536

IC-11521 2.880 8.307 8.400 7.792 19.260 7.373

DURGAJAY

2.430 6.360 7.333 5.527 27.027 3.829

FS-277 3.003 6.598 9.282 8.002 15.652 8.073

I9-1-55 4.300 9.520 9.890 8.882 28.129 22.440

RESPONSE OF AVENA SPECIES LEAF PHOTOSYNTHESIS AND STOMATAL CONDUCTANCE TO WATER STRESS (RATIO OF PHOTOSYNTHESIS(Pn) & STOMATAL CONDUCTANCE (gs) OF OAT SPECIES IN RESPONSE TO WATER STRESS AT VEGETATIVE AND FLOWERING STAGES OF CROP GROWTH.

SPECIES

PHOTOSY.

µMol(co2)

/m sq. sec inv.

S.C. (mmole / m sq.

Sec inverse)

Veg. Flo. Veg. Flo.Cont. Stress Cont. Stress Cont. Stress Cont. Stress

A.stri. 24.00 13.71 25.56 14.80 0.523 0.217 0.669 0.324A.bre. 20.02 13.06 27.16 12.76 0.344 0.187 0.632 0.261A.vavi.

26.17 12.88 28.78 13.16 0.636 0.215 0.742 0.342

A.abs. 22.91 10.46 19.47 12.95 0.493 0.192 0.564 0.264A.sat. 27.97 14.12 28.35 16.37 0.637 0.258 0.864 0.456A.mar. 21.32 11.16 24.61 13.21 0.564 0.219 0.712 0.432A.ste. 19.62 9.42 22.42 10.69 0.514 0.202 0.676 0.324CD at 5%Spe.(S)

1.68 0.79 0.06 0.03

Tre.(T) 0.90 0.42 0.03 0.01SxT 2.38 1.12 0.08 0.04

EFFECT OF ETHEREL ON SOME MORPHOLOGICAL & BIOCHEMICAL PARAMETERS IN SOYABEAN GERMINATING UNDER MOISTURE STRESS ( EFFECT OF MOISTURE STRESS ON GERMINATION, VIGOUR INDEX & GERMINATION RELATIVE INDEX)

TREATMENT STRESS LEVEL

GERMINATION% (TRANSFORMED)

VIGOUR INDEX (VI)

GERMINATIONRELATIVE INDEX

CONTROL 0 73.3 5644.10 20.00.4 53.3 2531.75 13.31.0 26.7 931.0 5.03.0 6.6 112.2 3.05.0 - - -

ETHREAL 0 86.6 11431.2 240.4 60.0 2940.0 191.0 26.6 984.2 73.0 26.6 604.4 35.0 - - -

CD at 5% level of significance

- 1.39 193 1.98

SOURCE: INDIAN JOURNAL OF PLANT PHYSIOLOGY Rajinder Sharma and Mohinder K. Grewal