effect drought stress on crops

1. Presented by:
PhD student: Mohaned Mohammed

2. Drought stress and tolerance mechanisms
in crops:
What is drought:
Is a period or conduction of unusually dry weather with a
geographic area where there is a lack of precipitation.
Drought stress account fro more production losses than all
other factors combined.
Fraction of world arable land subject to drought (abiotic
stress) 26%.
Drought is caverned by various factors, the most prominent
are:
 Extreme of temp
 Photon irradiance
 Paucity of water

3. The characteristic features of drought stress is low water
potential due to high solute concentration.
Low water supply causes soil mineral toxicities and can
make a plant more susceptible to damage from high
irradiance

4. Major reasons of drought
Atmospheric factors:
High temp
High wind
Air pollution
Soil factors:
• Low temp
• Excessive soil salinity
• Receding water content

5. Different type of drought
 Meteorological drought:
Due to prolonged period with less than average
precipitation.
 Agricultural drought:
Which affect crop production or ecology of range.
 Hydrological drought:
When the water reserves available in sources such as
lack and reservoirs fall be low statistical avreage.

6. Effect drought stress on plants
Effect on growth:
Reduction of turgor pressure, due to cell size will be
smaller.
Effect on photosynthesis:
Photosynthesis decreases due to distruption of PS II
(photo system II), stomatal closure and decrease in
electron transport.
Decrease in nuclear acid and proteins

7. Protease activity, RNAase activity, RNA hydrolysis and
DNA content falls down.
effect on Nitrogen metabolism.
Nitrate reductase activity, nitrite reductase activity
insensitive.
Effect on carbohydrate metabolism;
Loss of starch and carbohydrate translocation decrease.

8. Mechanism of drought tolerance:
 Drought scape:
It is defined as ability of a plant to complete its life cycle
before supply of water in soil is depleted. These plant
known as drought scapers.
 Drought avoidance:
It is ability of plant to maintain relatively water balance
despite a shortage of soil moisture.

9.  Drought tolerance:
It is ability of plant to withstand water deficit with low
tissue water potential.

10. Mechanisms of resistance to drought
Morphological response to drought:
 Increase in water absorption and transportation,
declination of transpiration.
 Developed root system and higher ratio of root to
shoot.
 Thick leaf
 Small leaf area
 Thick cuticle
 Developed veins and bundle
 Smaller and more stomata

11. Physiological and biochemical basis of drought stress
tolerance in plants:
 Increase in capacity of resistance to dehydration of
cytoplasm: rapid accumulation of proline,
glycinebetaine, and ion etc.
 Synthesis of specific proteins like LEA.
 Reduced ROS accumulation.
 Increase in antioxidative enzymes.
 Decreased efficiency of Rubisco.

12.  Phytohormone play vital role in drought tolerance in
plants.
Under drought condition, endogenous contents of
auxins, gibberellins, cytokine, usually decrease while
those of abscisic acid and ethylene increase.
 There are many signals that induce stomatal closure
among these the best known signal is ABA.

14. Summary
 In the days of global warming, the effect of drought
stress on crop productivity is expected to increase.
 The crop plant have involved certain resistance
mechanism agaist drought stress.
We should identify these mechanism and traits
And we introgress these into succeptable genotypes
 Only conventional breeding is not sufficient in
development of drought tolerant varieties.

15.  Non conventional approaches i.e. molecular breeding
can play a significant role in the sphere of abiotic stress
mainly drought tolerance.
 Genomic regions carrying drought tolerant gene can
contribute for abiotic stress tolerance.