SLIDE 1 – STRESS AND STRAIN
STRESS
When some factor of the environment interferes with the complete expression of genotypic potential of plant is called stress.
STRAIN
The effect of stress on plant condition is called strain.
SLIDE 2 – PLANT RESPONSE TO STRESS
PLANT RESPONSE TO STRESS
Extreme temperature
Flooding
Drought
Salt
Stress recognition
Stress transduction
Altered cellular metabolism
Physiological and developmental event
SLIDE 3 – DROUGHT
DROUGHT
The inadequacy of water availability, including precipitation and soil moisture storage capacity in quantity and distribution during the life cycle of a crop to restrict its yield potential.
SLIDE 4 – EFFECTS OF DROUGHT ON PLANT GROWTH AND DEVELOPMENT
Structures of membranes and organelles damaged
Hydration status decreased
Structures of macromolecules like proteins and nucleic acids damaged
Reduced cell division and expansion
Reduced osmoregulation
Increased root/shoot ratio
Reduced leaf area
Reduced photosynthetic rate
SLIDE 5 – EFFECTS OF DROUGHT ON MANGO
Vegetative flush greatly reduced
Reduction in number of leaves, flush length and leaf water content
Advancement of floral bud break by 2 weeks
Postponement in development of vegetative buds
SLIDE 6 – EFFECTS OF DROUGHT ON GRAPE
Tolerant crop due to large xylem vessels
Enhanced root length and reduced shoot growth
SLIDE 7 – EFFECTS OF DROUGHT ON BANANA
Sensitive crop
Carbon assimilation is affected
Flowering stage is most sensitive
Reduction in bunch weight and yield
Robusta, Karpuravalli and Rasthalli are sensitive varieties
SLIDE 8 – EFFECTS OF DROUGHT ON PAPAYA
50 % reduction in leaves
Reduction in number of flowers by 86 %
Reduction in fruits by 58 %
Growth and development of fruit retarded
SLIDE 9 – DROUGHT RESISTANCE
The mechanism causing minimum loss of yield in a drought environment relative to the maximum yield in a constraint free environment.
SLIDE 10 – MECHANISMS OF DROUGHT RESISTANCE
Drought escape – avoiding the period of drought by early maturity
Dehydration avoidance – retaining higher hydration under water stress
SLIDE 11 – DEHYDRATION AVOIDANCE
Reduced transpiration
Osmotic adjustment
ABA synthesis leading to stomatal closure
Cuticular wax
Leaf pubescence
Deep root system and large root length density
SLIDE 12 – DEHYDRATION TOLERANCE
Lower level of changes in chemical activity of water and solute concentration
Maintenance of membrane integrity
Synthesis of mannitol and polyethylene glycol
Proline accumulation
SLIDE 13 – SALINITY
Accumulation of soluble salts in the root zone causing detrimental effects on plant growth and development.
Area under salt affected soils in India is 6.74 M ha.
SLIDE 14 – TYPES OF SALT AFFECTED SOILS
Saline soils – chlorides and sulphates of sodium, calcium, magnesium and potassium
Alkali or sodic soils – sodium carbonate is the dominant salt
SLIDE 15 – EFFECT OF SALINITY STRESS IN FRUIT CROPS
Osmotic stress to roots
Nutrient imbalance and reduced uptake
Leaf injury
Growth inhibition
Poor fruit bearing and reduced yield
SLIDE 16 – SALINITY EFFECT ON MANGO
Increase in irrigation water salinity reduces N, K, Ca and Mg content in leaves without affecting P and S.
SLIDE 17 – SALINITY EFFECT ON PAPAYA
Growth reduced by 50 % at 4 dS m⁻²
Mortality occurs above 6 dS m⁻²
SLIDE 18 – SALINITY EFFECT ON BANANA
Leaf necrosis
Reduced pseudostem thickness
Delayed flowering
Reduced finger size
Low quality bunches
SLIDE 19 – SALINITY RESISTANCE
Resistance to salinity induced water stress through osmoregulation
Resistance to salinity induced ion toxicity by maintaining low salt concentration in cytoplasm
SLIDE 20 – ION EXCLUSION AND SALT TOLERANCE
Reduced uptake of Na⁺ and Cl⁻ ions
Example: Citrus – Rangapur lime and Cleopatra mandarin
Excretion of excess salts through salt glands or cellular compartmentation
SLIDE 21 – HEAT / HIGH TEMPERATURE STRESS
Adverse effects on plants of temperature higher than the optimal temperature.
SLIDE 22 – EFFECTS OF HIGH TEMPERATURE STRESS
Sunburn on leaves, branches and stems
Leaf senescence and abscission
Inhibition of shoot and root growth
Fruit discoloration and damage
Reduced photosynthesis
Impaired reproductive processes
SLIDE 23 – HEAT STRESS EFFECT ON MANGO
Floral induction at 15°C day and 10°C night
Vegetative induction at 30°C day and 25°C night
Low temperature increases male flowers
High temperature increases hermaphrodite flowers
SLIDE 24 – HEAT STRESS EFFECT ON GRAPE
Advanced harvest
Higher sugar concentration
Low acidity
Alteration in aroma compounds
SLIDE 25 – HEAT STRESS EFFECT ON BANANA
Growth and production affected
Leaf production and growth affected
Growth sustained up to 39.2°C
SLIDE 26 – HEAT STRESS RESISTANCE
Heat avoidance through transpirational cooling
Heat tolerance by withstanding high internal temperatures
SLIDE 27 – CHILLING STRESS
Tropical fruit crops are chilling sensitive.
SLIDE 28 – CHILLING STRESS AT PLANT LEVEL
Reduced germination
Poor seedling growth
Stunted growth
Wilting
Chlorosis and necrosis
Poor fruit set
Pollen sterility
SLIDE 29 – CHILLING STRESS AT CELLULAR LEVEL
Membrane damage
Protein changes
Decline in photosynthesis
Reduced chlorophyll synthesis
Increased respiration
Toxicity injuries
SLIDE 30 – CHILLING TOLERANCE
Chill hardening by prior exposure to low temperature
Improved chlorophyll accumulation
Better germination, fruit set and pollen fertility
SLIDE 31 – MANAGEMENT PRACTICES OF ABIOTIC STRESSES
Modification of cultural practices
Irrigation during post fruit set
Application of rice husk ash or composted coir pith
Incorporation of crop residues and green manures
Farm ponds for runoff harvesting
Potassium amendment to maintain K:Na ratio
Micro irrigation techniques
Partial root zone drying
Deficit irrigation
Subsurface irrigation
SLIDE 32 – TOLERANT FRUIT CROPS
Ber, Aonla, Guava, Grape, Karonda, Jamun, Phalsa
SLIDE 33 – TOLERANT ROOTSTOCKS
Grape – 110R, 99R, 1103P, Dogridge, Salt Creek, B2-56
Mango – Starch, Peach, Kensington, Mylepelian, Olur, Kurukkan, 13-1, Gomera-1
SLIDE 34 – BIOTIC STRESS
Disease is the series of invisible and visible responses of plant cells and tissues to pathogenic microorganisms leading to impairment or death.
SLIDE 35 – HOST, PATHOGEN AND DISEASE TRIANGLE
Host – Plant affected by disease
Pathogen – Organism producing disease
Environment – Influences disease development
SLIDE 36 – RESISTANCE AND TOLERANCE
Vertical resistance – race specific
Horizontal resistance – race non-specific
Tolerance – infection occurs with little or no yield loss
SLIDE 37 – PESTS
Sucking pests – aphids, jassids, thrips, white fly, mites
Tissue feeders – stem borers, fruit borers, weevils, beetles
SLIDE 38 – MECHANISMS OF PEST RESISTANCE
Non-preference (antixenosis)
Antibiosis
Tolerance
SLIDE 39 – CONCLUSION
Climate change intensifies biotic and abiotic stresses causing morphological, physiological and biochemical changes. Adoption of improved cultural practices, irrigation methods and tolerant crops is essential.
SLIDE 40 – FUTURE LINE OF WORK
Enhancement of genetic diversity
Collection of tolerant genotypes
Identification of tolerance traits
Development of tolerant and transgenic cultivars and rootstocks
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