The document discusses various mechanisms of drought adaptation and mitigation in crops. It describes two main types of drought adaptation: (1) escaping drought by completing the lifecycle before drought conditions occur, and (2) drought resistance through mechanisms of drought avoidance and tolerance. Drought avoidance allows plants to maintain a favorable water balance through traits like reduced transpiration and increased water uptake. Drought tolerance enables plants to endure drought stress through traits like resistance to dehydration and leaf collapse. The document provides many examples of structural and physiological traits that confer drought adaptation in different crops.

2. INDIRA GANDHI KRISHI VISHWAVIDHYALAYA
RAIPUR
RANI AVANTI BAI LODHI COLLEGE OF
AGRICULTURE
AND RESEARCH STATION CHHUIKHADAN
K.C.G.
Presentation to:-
Crop adaptation and mitigation to
drought.
Course
title:-
Rainfed agriculture and watershed
management.
SESSION :- 2022-23
Course code:-AGRO – 5321.
Submitted
to
Miss hemin
verma
(Assistant professor of
agronomy department.)
RABL CARS Chhuikhadan
Submitted by
Durgesh kumar
raj
Std. ID :-
20201488.
B.Sc.(Ag.) 3rd year 2nd
sem.
RABL CARS

3. • Crop Adaptations :-
• The ability of crop to grow satisfactorily
under water stress is called drought
adaptation.
• Adaptation is structural or functional
modification in plants to survive and
reproduce in a particular
environment.
• Crops survive and grow under moisture stress
conditions mainly by two: (i) escaping
drought and (ii) drought resistance.

4. Fig. Flow chart showing different mechanisms for overcoming

5. • Plants may escape drought stress by
completing their life cycle before the advent
of environmental conditions causing drought
stress. Such plant is called "drought escaper".
• Many desert plants, the so-called
ephemerals, germinate at the beginning of
the rainy season and complete their life cycle
in the rainy season itself. These plants are
A. Escaping drought :-

6. Eg: Cultivated millets produce mature seeds
within 60 days from germination. Short
duration pulses like cowpea, greengram,
blackgram.
B. Drought resistance: is capacity of plants
to endure the drought condition without
suffering any irrevocable injury.
i.e. growing successfully and maturing
properly.
1. Drought avoidance2. Drought
tolerance

7. 1.Drought avoidance
:-
is the ability to maintain a favourable water
balance and turgidity even when exposed to
drought conditions, thereby avoiding stress and
its consequences.
• A favorable water balance can be achieved
by
I. Mechanism for conserving water in
plants.
II. Mechanism for improving water uptake
from soil.

8. • Mechanisms for conserving water in
plants (Water savers) :-
a. Stomatal mechanisms:-
• Drought resistant varieties are capable of
regulating the stomatal mechanism and
closingstomata when drought prevails.
• Eg:- Stomata remain open throughout day in
semi dwarf wheat whereas in tall variety, it is
open for only few hours in the morning hours,
remaining time closed thereafter even under
favorable conditions of soil moisture and

9. b. Increased photosynthetic
efficiency:-
• C4 plants have high potential activity due to
the caboxylating enzyme namely
phosphoenolpyruvic acid carboxylase which
has high affinity for CO2. C4 plants are more
drought resistant than C3 plants.
• Ex: sorghum, pearl millet, maize, sugarcane,
soyabean, finger millet, grasses,
Cynodondectylon, sudan grass etc.

10. c. Low rates of cuticular transpiration :-
• Plants use to develop cutine, a waxy coating,
over cuticles for reducing the
cuticulartranspiration of water.
• The dwarf wheat varieties of durum group,
triticales, barley use to get the waxy coating
under rainfed conditions to survive the
drought. Xerophytic plants such as cactus
have this character.

11. d. Decreasing
transpiration :-
• Some plants produce lipid on the surface and
provide a covering to reduce traspiration.
• Eg: Soybean,
sorghum.
e. Reduced leaf
area:-
• The water loss through transpiration is
directly proportional to the leaf area and
plants can survive longer if they can reduce
their leaf surface area.

12. • Xeromorphic plants have the ability to
reduce their transpiring surface like grasses
and find fit for drought conditions.
f. Leaf surface:-
• Leaves with thick cuticle, waxy surface and
spines etc. are common and effective in
reducing the transpiration rate.
• Pubescence increases leaf reflectance and
reduces solar radiation incidence.

13. g. Effect of awns :-
• Awns have chloroplasts and stomata and can
photosynthesize.
• The contribution of the awns to the grain is 12
percent of that by the entire plant.
• E.g. Wheat and rice.

14. • Mechanism for improving water uptake
from soil:-
• The mechanism of water uptake totally
depends upon the root system of the plants
whichmay be described as under
a. Effective root system
:-
• Deeper roots with well branched, rapidly
growing and extensive root hairs absorb more
water.
• Thus, the density of hairs per unit volume of
soil and the number of secondary hairs are
the most important ones.

15. • It is observed that sorghum has nearly twice
as many small branch roots per unit length
of main roots as has maize and it is
assumed that it is one of the main reasons
for its greater drought resistance. Sorghum
is regarded as camel of desert.
• Certain plants have the ability of their root
system to penetrate relatively dry soils
• Eg: Oats, wheat, barley show little
penetration of the soil, at or below the
witting point.

16. b. Root to shoot
ratio :-
• Under dry conditions the growth rate of the
roots considerably exceeds that of the shoots.
c. Increase in liquid phase
conductance :-
• To maintain higher water potential in plants,
not only water uptake is important, but also
conductance.
• Lowering of water can be achieved by
increasing either diameter of xylem vessels or
their number.

17. c. Osmotic Potential of the plants :-
• The water movement in plants depends upon
their osmotic potential.
• The stress induced break down of
carbohydrates and proteins increase the
concentration of solutes in the cell sap
resulting in reduction of osmotic potential.
• These Plants survive for relatively longer
period.

18. 2. Drought tolerance :-
• Drought tolerance is defined as tolerance of
the plants to a level of stress at which 50%
of the cells die.
• Drought tolerance is either by mitigating
stress or by showing high degree of
tolerance.
a. Mitigating stress
:-
• The simplest way of mitigating stress is by
resistance to dehydration and prevention of
leaf collapse.

19. - The osmotic pressure of crop plants 10-20
atm
i. Resistance to
dehydration:
• The maintenance of higher osmotic pressure
by accumulating higher amounts of solutes
prevent dehydration.
- The osmotic pressure of xerophytes 30-40
atm
- The osmotic pressure of Halophytes 100
atm or more

20. ii. Prevention of leaf
collapse:-
• Thick cell wall, sunken stomata, lipid or waxy
coating over leaves, presence of spines etc.
prevent cell collapse by reducing the
transpirational loss of water.
• Thus leaf collapse is avoided and plants are
saved.
b. High degree of
tolerance:-
i. Reducing metabolic strain or plastic
strain:-
• Adverse influence of drought on metabolism
of plants is known as metabolic strain.

21. • In xeromorphic plants, higher the
dehydration, lower will be the dehydration
compensation point. "Dehydration
compensation point":
• This is the water potential at which rates of
photosynthetic CO2 absorption and
respiratory CO2 evolution are equal, so that
net photosynthesis equals zero".
• Drought resistant plants have the capacity to
synthesis "Proline" which appears to be
associated with drought tolerence.

22. ii. Heat
resistance:-
• The temperature at which respiration and
photosynthesis are equally rapidis called the
"temperature compensation point".
3. Avoiding stress :-
• Stress avoidance is the ability to maintain a
favourable water balance, and turgidity even
when exposed to drought conditions, thereby
avoiding stress and its consequences.

23. • A favorable water balance under drought
conditions can be achieved either by:
• (i). conserving water by restricting
transpiration before or as soon as stress is
experienced; or
• (ii). accelerating water uptake sufficiently so
as to replenish the lost water.