Stress Tolerance in pLants.pptx

Stress tolerance in plants

1. Khwaja Moinuddin Chishti Language University (Department of Biotechnology) Topic – Stress Tolerance in Plants Submitted to – Dr.Manvendra Singh Submitted By – Sparsh Tiwari

2. Stress Tolerance in Plants

3. Stress Any deviation in optimal condition of any factor essential for its growth will lead to aberrant change in physiological processes and due to this plant body will experience tension and this state referred as plant stress. Reduction in growth, yield and death of the plant or plant part. Stress may be caused due to biotic (disease, herbivores) or abiotic (Physical and chemical) factors(Nilsen & Orcutt, 1996).

4. ABIOTIC STRESS BIOTIC STRESS (A) Physical stress (B) Chemical stress Drought and Flooding Temperature Light Radiation Wind Air Pollution Heavy Metals Pesticides Insecticides Toxins Soil pH Alkanity Allelopathy Competition Disease Pest Human activities Classification of stress

5. Strategy to face the stress conditions Escaper: Completing their life cycle before the occurrence of a stress Stress Avoider: Achieved through morphological changes in the plant, such as reduced stomatal conductance, decreased leaf area and increased root/shoot ratios. Stress Tolerant: Sustain the effect of stress without dying or suffering injury. Achieved by specific physiological, biochemical and molecular mechanisms at cell level which include specific gene expression and accumulation of specific proteins.

6. Major stresses occurred in plants (1) Water Stress: The availability of excessive (flooding) or inadequate (drought) supply of water is called the water stress Changes in plant growth Loss of turgor that affects the rate of cell expansion and ultimate cell size. Affects translocation indirectly by altering the source to sink relationships for assimilates. Changes in structure of macromolecules by removal of water Inhibition of cell expansion results in a slowing of leaf expansion. The dehydration of mesophyll cells inhibits photosynthesis

7. Con t i.. Decrease in turgor causes stomatal closure ABA inhibits shoot growth, further conserving water and root growth appears to be promoted, Osmotic adjustment- Certain organic compounds such as sucrose, amino acids (especially proline and betaine), inorganic ions (especially K + ) and several others that lower the osmotic potential and thus, maintain water potential of cells without limiting enzyme function .

8. Loss of turgor Impaired mitosis Drought stress (Reduced water availability ) Obstructed cell elongation Dim i nished growth Limited cell division

9. (2) Salt stress Affects plants adversely in two ways: (i) High solute content in rooting medium creates water stress by decreasing osmotic potential and Direct toxic effect of higher concentration of ions. (ii) ( 1) . H a l o p h y t es ca n grow co m fort a bly i n sa l ine s oils wi t h h i gh sa l t concentrations. (2 ). Glycophytes: Cannot grow in the presence of high concentrations of salts . But manage to grow in saline conditions by adopting some mechanisms as : Accumulation of sugars in leaves Compartmentalization (checked from reaching to photoshythetic parts) (Jacoby, 1965)

10. Mechanisms of Tolerance l. Succulence that may lead to dilution of intracellular salt such as occurs in Salicorma sp. Pre s e n ce o f s a lt excr e t i ng gla n ds that re d u c e the concentration of salt in the plant e.g. Frankenia, Spartina D e ve l op m ent o f s m a l l l e av e s, wat e r s t or a ge hai r s and aerenchyma Sometimes there is synthesis of organic solutes that aids in the maintenance of turgor

11. Difference between salt stress from ion stress Salt Stress: If the salt concentration is high enough to lower the water potential by 0.05 to 0.1 MPa then the plant is under water stress If the salt concentration is not this high the stress is ion stress and may be caused by one particular species of ion

12. (3) Temperature Stress Divided into the effects of temperature that cause High temperature injury Chilling injury Freezing injury

13. High temperature injury Respiration rate increases and photosynthetic rate decrease, tissue may deteriorate because the lack of life supporting energy The denaturation and aggregation of proteins occur RUBISCO and other enzymes of carbon metabolism are adversely affected Change in the viscosity of the lipid components of the cells to a more fluid state High temperatures reduce the membrane stability of various cellular membranes causing loss of physiological functions and cell integrity Some plants avoid high- ~temperature injury Angle and arrangement of the leaves Thick cuticle and leaf hairs (improves conductive cooling)

14. Chilling injury : Injury which causes due to low but above zero degree centigrade temperature is called chilling injury. These chilling temperatures are too low for normal growth but not enough for ice formation Roots are chilled, the plants may wilt The chilling sensitive physiological functions include inhibition of photosynthesis, reduced carbohydrate translocation, lower transpiration rates, inhibition of protein synthesis and increased degradation of existing proteins

15. Freezing injury: occurs at temperatures below the freezing point of water (below C) and primarily the aqueous phase in the apoplast freezes. At 0°C there is a phase transition in water from liquid to solid. Ice crystals develop in the intercellular spaces and cell walls large polysaccharides and proteins facilitate ice crystal formation, which are called as ice nucleators

16. (4) Light Stress: Alteration in light intensity whether a deficit or excess, will result in a disruption of plant metabolic processes. Low light intensities below the compensation point lead to starvation with carbohydrates used as substrate for respiration first and then other source of energy. In high intensity light photosynthetic performance of plants is depends upon relationship between photo inhibition of photosynthesis and the degree of chlorophyll destruction.

17. Ultraviolet radiation The electromagnetic radiation from the sun contains about 7% ultraviolet at sea level. Alteration of protein and lipid membrane components by ultraviolet may alter membrane permeability and ionic balance. Such events also cause an inhibition of photosynthesis and respiration

18. (5) Nutrient Stress If plant takes less than optimum quantity of any essential mineral than the situation is referred as deficiency and more than optimum than situation is referred as toxicity of that mineral Deficiency (nutrient Stress) of an element results from : Amounts and concentrations present in the soil Form in which they exist Soil pH

19. Conti… Elements such as calcium, boron, and iron often become deficient in the younger parts of the plant because of little or no retranslocation and poor phloem mobility. Similarly if such ions are applied foliarly there is little basipetal movement. Deficiency Symptoms A symptom is any perceptible change in known structure appearance or function. Such things as leaf yellowing (chlorosis), death (necrosis), lesions, malformations, reduced Growth and yield are all considered to be symptoms and occur as a result of nutrient deficiency. Toxic level of Zink, Copper and Nickel occurs frequently in soil.

20. (6) W ind Excessive water loss through transpiration causes partial or complete closure of the stomata may ensue which will restrict the diffusion of carbon dioxide into the leaves. As a result, there will be a decrease in the rate of photosynthesis, growth and yield (Edmond et al., 1978). Lodging or toppling of plants.

21. (7) Air P ollution Chemical Symptoms Sensitive Plants Chlorine Bleaching, leaf tip and margin browning, drooping of leaves, yellow spots Peach, Oak, Pine Fluorides Leaf tip and margin yellowing (chlorosis), dwarfing, leaf abscission, decreased yield Grap e , Blu e berr y , Apricot Nitrogen oxides Brown growth spot on leaf, suppression of Apple, Pinto beans Sulphur dioxide Bleached spots on leaf, chlorosis, early abscission, reduced yield Apple, Oats, Pumpkin Ozone Reddish brown flakes on leaf surface, bleaching, suppression of growth, early abscission, premature ageing Apple, Grapes, Pine

22. Some examples of air pollution : Citrus fruits is extremely sensitive to fluoride Cotton is very sensitive to ethylene A crop in a tightly closed greenhouse will soon deplete the CO 2 concentration which reduces growth and production by slowing or stopping photosynthesis

23. Biotic Stress Biotic stress is stress that occurs as a result of damage done to plants by living organisms, such as bacteria, viruses, fungi, parasites, beneficial and harmful insects, weeds, and cultivated or native plants.

24. Mechanical barriers Cork Layers : Formation of cork cells in areas surrounding penetration points and forming a necrotis spot and the isolation by cork layers. Tyloses: Restricts pathogens transport through xylem vessels Lignitubers : A sheath, may form around the invading hypha increasing the mechanical strength of cell walls Biochemical resistance Passive – already present in plants (Phenolic Glucosides, Glucose Esters etc) and toxic to potential invaders Active – induced by pathogen invasion (Caffeic Acid, Scopoletin and Orchinol) Disease control strategies in plants

25. Cont i … Hy p e r sen s it i ve r e s p o n s e ( H R ) : L i m ited no . o f c e lls die, pathogen get isolated in localized necrotic tissue Phyt o alexin s : low m olecular m ass se c o n dary metabolites with antimicrobial activity (Hückelhoven, 2007)