stress physiology.pptx

stress physiology is related to plant physiology in which how can plant survive in adverse condition

1. S alinity Stress, Metal Toxicity, Freezing, Heat and Oxidative Stress B y Dr. Gunmala Gugalia Associate Professor Department of Botany Sangam University, Bhilwara (Rajasthan), India

2. Table of contents Definition of stress Type of stress Abiotic stress Water stress Temperature stress Freezing stress Chilling stress Salinity stress Oxidative stress B iotitic stress

3. Definition of stress Any external factor that can show disadvantageous effect upon organism is called stress

4. STRESS Abiotic Stress Biotic stress water Temperature Salinity 0xygen Herbivorous Pathogen Heat stress Cold stress Chilling Freezing

5. Stress resistant mechanism: Stress resistance in plant is of following two types……….. 1.Avoidence 2.Tolerance 1 . Avoidence - internal environment is created in such manner within the plant that overcome the environment stress. Ex . Succulent plant consume water that avoid water stress. By increase transpiration in leaf plant maintain cooling and avoid heat stress. 2. T olerance- plant having tendency to grow in stress condition . Ex .Mangrove plant tolerate excess salt by pneumatophores and viviparous germination. Tolerance is increased by (2) type 1,acclimation 2.adaptation

6. Types of tolerance : A cclimation It occur for short duration it is not transmitted to next generation Ex. Osmotic adjustment A daptation It is genetic variation evolved in population by multiple generation through the natural selection Ex. Hydrophytic plants X erophytic plants

7. Abiotic stress Stress caused by climatic factor is called ‘’abiotic stress’’ water stress T wo type of water stress: 1.Drought stress 2.Flood stress

8. Drought stress : It is caused by insufficient precipitation P lant develop various drought resistance capabilities A bility to maintain tissue hydration EX . Cactus A bility to maintain function dehydrate condition This type of plant complete their life cycle in wet season The entry of drought leaf area is decreased Root to shoot ratio is increased due to the ratio of auxin and cytokinin In drought condition ABA hormone condition i s high that promoted stomata closer I n drought condition excess wax disposition is promoted in the leaf that prevent excess water

9. Adaptation Hydrophytic plants develop Aerenchyma which is responsible for storage as well as transpot of Oxygen Free floating plants having air chamber Air chambers are formed by program cell death

10. Flood Stress In flooded soil microspores get filled with water water soil cause Hypoxia and later it causes Anoxia in hypoxia root respiration is inhibited that’s why plant show wilting in hypoxia condition anaerobic bacteria are activated that trigger reduction of various ions reduced ions are easily absorbed by root that’s why is cause mineral toxicity

11. Temperature stress 1.High tem. Stress 2. Low tem. Stress 1.High temperature stress : also known as heat stress both photosynthesis and respiration are inhibited at high temperature high temp can lead to loss of 3D structure of certain enzyme Effects of heat stress heat stress trigger dehydration in plant reflective wax on leaf surface leaf size reduced presence of sunken stomata During heat stress condition plant synthesize various heat shock protein

12. 2. Low Temperature Stress When the temperature is low for normal growth but not enough for ice formation 1. Chilling stress: Effect Chilling stress : slow growth loss of membrane function at low temperature enzymatic activity get lost decrease in photosynthesis

13. Acclimation Strategy Against Chilling Stress Chilling sensitive plant having large chain saturated fatty acid Slow growth Decrease in photosynthesis

14. 2. Freezing Stress: At very low temperature water is converted ice in cellular space Effect of freezing stress Shrinkage of protoplast Destruction of chlorophyll Change in membrane potential Ice formation in intercellular space results in cellular water movement toward ice

15. Acclimation strategy against freezing stress Formation antifreeze protein That prevent ice crystal formation upto temp. without lowering the freezing point they bind to ice surface preventing their growth Thermal hysteresis protein

16. Metal stress Heavy metal toxicity means excess of required concentration or it is unwanted which were found naturally on thy earth and become concentration as a result of human caused activities Copper, manganese, lead, cadmium, nickel, iron, zinc, chromium is heavy metal heavy metal are natural components can not be degraded some of heavy are (Fe, Cu, and Zn) essential for plant their uptake in excess to t he plant requirements result in toxic effects

17. Effect of cupper on plant: Function of copper in oxidation reduction Cu work as electron receptor copper is an essential metal for normal pant growth and development Toxic effects reduces biomass and seed production Reduces the root growth Wilting ,curling , of leaves and apical part turned into white

18. Effect of zinc on plant: Function of zinc Zinc help a plant to produce chlorophyll and synthesis of plant hormone IAA TOXIC Effect Stunted plant growth

19. Effect of manganese on plant: Function of manganese : Give rise to manganese and copper deficiencies Toxic effect Decrease in growth and development

20. Salinity Stress Salinity stress is synonymous with sodicity . High temperature also trigger salinity because at high temperature rate of transpiration and evaporation is increased. Salinity decrease the plant growth and photosynthesis yield . Excess salt in the soil reduce the water potential of the soil and the soil solution unavailable to plant . Based on the response to high concentration of solt plant can divided into two group 1. Halophytes 2. Glycophytes

21. Halophyte : this type of plant can tolerate high solt concentration G lycophyte : this plant show of degrowth in salt concentration is increased high salt concentration destruction is most common symptom Effect on plant growth and development On growth : decrease rate of leaf growth after an increase in soil salinity due to the osmotic effect of the salt ground the roots . Increase in soil salinity cause leaf cells to loose water. Reduction in cell elongation . Germination : increased osmotic pressure of the soil solution which restricts the absorption and enter of water into the seed . Vegetative growth : accumulation of high concentration of sodium and chloride ion in chloroplast photosynthesis is inhibit .

22. Plants use different strategies to avoid salt injury: Casparian strip is present at endodermis & prevent the movement of unwanted material Sodium ion enter root passively so root cells must use energy to extrude sodium ion actively back to the outside solution . Phytochelatin : phytochelatin form complex with various heavy metal like cadmium ,mercury , prevent the cellular toxicity During osmotic adjustment plant synthesis various solute molecule that is responsible for lowering the of root hair. This solute is called compatible solute .

23. Oxidative stress The oxidative stress is the stress due to production of Reactive Oxygen Species (ROS) oxidative stress cause a imbalance between the reactive oxygen species and the antioxidant oxidative stress is induced by a wide range of environmental factors including pathogen invasion, oxygen shortage the reactive species are singlet oxygen, superoxide radical, hydrogen peroxide and the hydroxyl radical which are the by-products of biological reaction. A common feature of ROS is the capacity to cause damage to protein, DNA , lipid and the maximum damage is caused by singlet oxygen and the hydroxyl radical

24. Impact of Oxidative Stress on Plants On plasma membrane structure when excess light energy is absorbed by plant during photosynthesis harmfully reactive oxygen species are produced these reactive oxygen species break down important structure such as protein of membrane prevent them from functioning properly root respiration rate and metabolism are affected even before oxygen is completely depleted from the root environment anoxic or hypoxia roots lack sufficient energy to support physiological processes on which the shoot depend hypoxia also accelerates production of the ethylene precursor in root ethylene con. Become high in the cell of leaves it prevent the leaves to wilt because it maintains the turgor pressure of cells of leaves

25. Defence Mechanism The organisms evolved varies strategies to protect themselves against oxidative stress Plants use antioxidant defence mechanism which are if two type E nzymatic agents : super oxide dismutase enzymes catalase glutathione Non- enzymatic agent : carotenoid ascorbic acid The intercellular level of H is regulated by catalase. Ascorbate functions as a reductant for many free radical and minimize the damage caused by oxidative stress

26. Questions Q. 1. Following are some statements about low temperature P. fatty acid composition isolated from chilling resistant and chilling sensitive plant differs significantly Q. ratio of unsaturated fatty acid to saturated fatty acid is lower in chilling resistant species R. the cellular water does not freeze even at because of the presence of solutes and other anti freeze proteins S. heat shock proteins do not play any role during low temperature stress which one of the following combination of above statement is correct a. P and Q b. P and R c. Q and R d. Q and S Ans. b

27. Q.2. Which of the following phytohormones is produced under water deficient conditions and play on important role in the tolerance response of plant to drought and high salinity A. a bscissic acid B. c ytokinin C. ethylene D. gibberellin ans. A Q.3. Which one of the following mineral deficiency will first be visible in younger leaves A. calcium B. Nitrogen C. Zinc D. Molybdenum ans. A

28. Q. 4. Following are some statements related to osmotic stress in plant A. The accumulation of ions during osmotic adjustment is predominantly restricted to the vacuoles B. In order to maintain the water potential equilibrium within the cell other solutes called as compatible solutes or compatible osmolytes accumulate in the cytoplasm C. galactose is one of the compatible osmolites involved in osmotic stress in plant D. there are three mainly group of molecules that frequently serve as compatible solutes which one of the following combination of above statement is correct a). A,B and C b).B,C and D c). A,B and D d). A,C and D ans.c

29. Q. 5. For metabolic engineering in plant having Improved tolerance to osmotic stress mannitol is overproduced because it: a ). lower the water potential in the plant cell b). Increases the water potential in the plant cell c). Lowers membrane potential in the plant cell d). Increases membrane potential in the plant cell ans. a

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