Water and it's relation with crop

1. WATER RELATION TO CROP
PLANTS

2. WATER RELATION TO CROP PLANTS
• Water is medium of life
Significance of water for plants
1. Water is important for survival
2. Water is important for germination
3. Water is important for photosynthesis
4. Metabolic processes
5. Uptake of nutrients
Mass flow ----› transpirational pull

3. CONTINUE......( SIGNIFICANCE )
• Maintain cellular turgor pressure ( which facilitates growth of plants )
• Water regulates leaf temperature
• Stomatal regulation
• Chlorophyll a synthesis ( thylakoid membrane ) chlorophyll synthesis
• Enzymatic reactions
• Photolysis ( produce electron )
• Hydrolysis ( break down of any compound in presence of water )

4. GERMINATION
Phases of germination
1. Imbibition ( uptake of water )
2. Metabolic phase ( lag phase )
3. Redicle Protrusion ( Emergence )
• Water move due to water potential gradient
• Seed not shift in 2nd phase until it up take 1/3 of water of its dry weight

5. CONTINUE.........
Hydrolysis enzymes
• The enzymes which active in presence of water
Strach---amylase------› sugar ( plant useable )
Stored food ( reserves )
These enzymes break down stored food into smaller units ( Alpha & beta amylase )
Redicle protrusion:-

6. PROPERTIES OF WATER
• Woody plants 50% water
• Herbaceous are 80% water
• Protoplasm more than 90% water
Properties:-
Polarity : water is a polar molecule
Which have positive & negative charges
H20------------ H+ + oH-

7. WATER IS POLAR
• In each water molecule, the oxygen atom attracts
more than its "fair share" of electrons
• The oxygen end “acts” negative
• The hydrogen end “acts” positive
• Causes the water to be POLAR
• However, Water is neutral (equal number of e- and
p+) --- Zero Net Charge

8. CONTINUE....
• One oxygen can attach to two Hydrogens
• Angle between two Hydrogen ions is 105°
Hydrogen bonding
• More strong hydrogen bonding ( no splitting )
• Need more energy to convert into vapour phase
• Insect floating swimming due to hydrogen bonding

9. INTERACTION BETWEEN WATER MOLECULES
Negative Oxygen end of one water molecule is attracted to the Positive Hydrogen end of another
water molecule to form a HYDROGEN BOND
Surface tension
Strength by which water molecules are attracted towards each other at the top surface
Components of capillary action
Cohesion:- Attractions between towards each other ( similar molecules )
Adhesion:- Attraction b/w two different substances
•Attraction between particles of the same substance ( why water is attracted to itself)
•Results in Surface tension (a measure of the strength of water’s surface)

10. ADHESION
• Attraction between two different substances.
• Water will make hydrogen bonds with other surfaces such as
glass, soil, plant tissues, and cotton.
• Capillary action-water molecules will “tow” each other along
when in a thin glass tube.
• Example: transpiration process which plants and trees
remove water from the soil, and paper towels soak up
water.

11. ADHESION CAUSES CAPILLARY ACTION
Which gives water the ability to
“climb” structures

12. WATER IS LESS DENSE AS A SOLID
• Density ( liquid density 1g/dm3 )
The density of water decreases when it converted from liquid to solid form.
• Ice is less dense as a solid than as a liquid (ice floats)
• Liquid water has hydrogen bonds that are constantly being broken and reformed.
• Frozen water forms a crystal-like lattice whereby molecules are set at fixed
distances.

13. Water Existence
• Water exist in all three phases
1. Liquid
2. Solid
3. Gas
High heat of vaporization
• Water has high heat of vaporization
• Amount of energy to convert 1g or a substance from a liquid to a gas. In order for water to evaporate, hydrogen bonds must
be broken.
• As water evaporates, it removes a lot of heat with it. Water requires 44kJ / mol ( 540 calories ) to convert from liquid to gas. (
H.B )
• It provides cooling effect (As water evaporates, it removes a lot of heat with it)
• Water vapor forms a kind of global ‘‘blanket” which helps to keep the Earth warm. Heat radiated from the sun warmed
surface of the earth is absorbed and held by the vapor.

14. WATER HAS HIGH SPECIFIC HEAT
Amount of heat required to increase or decrease 1°C temperature in 1g of Molecules(water)
• Water posses high specific heat . It help to regulate temperature
• Water resists temperature change, both for heating and cooling.
• Water can absorb or release large amounts of heat energy with little change in actual
temperature.
• Temperature maintain no fluctual change e.g. Xerophytes ( stored water )
• Three-fourths of the earth is covered by water. The water serves as a large heat sink
responsible for:
• Prevention of temperature fluctuations that are outside the range suitable for life.
• Coastal areas having a mild climate
• A stable marine environment

15. CONTINUE...
• Water is transparent to light ( Life exist due to transparency of water )
• Solvent for Life: Water is a universal solvent ( can disolve easily other charged
ions )
• Water provides the basis for pH system
• Water does not react directly
H2O  H+ + OH-
Hydrogen Ion Hydroxide Ion
Acid Base

16. WATER STRESS
Stress:-
1. Any environmental factor that negatively effected the growth & survival of plants
2. Any environment factor that hampers/ decrease in the growth of organism.
Water stress:-
Lack of water or presence of to much water that negatively effects the growth & survival of
plants.
• Water deficit conditions leads to drought stress
• Excess water supply
• water logging
• submergence
• Flooding

17. CONTINUE ...
• Water logging:-
• Saturation of soil with water is called water logging
• Saturation of air hole with water is called water logging
Root growth stop due to water logging because oxygen not available at root tips.
Defusion is 10,000 times less in water than in air
• Submergence:-
When the whole plant is submerged in water that condition called Submergence
( Decrease gaseous exchange)

18. CONTINUE...
• Flooding:-
• When a part of plant submerged in water is called flooding
Drought stress:
Unavilabilty of water for certain period of time
Lack of precipitation for a certain period of time that is enough to cause soil moisture
depletion & damage to plant
1. Meterological drought
2. Hydrological drought
3. Agricultural drought

19. CONTINUE....
Meterological Drought:
When rainfall / precipitation in a particular area is less than average climatological mean of
that area.
Hydrological Drought:
Hydrological drought is the depletion of soil water table that cause low/ below stream flow
and drying of lakes , rivers & reservoirs
Agricultural Drought:-
When the Precipitation is insufficient to sustain the agricultural productivity.
Lack of precipitation for a period of time that Is lesser to meet the demand of seasonal
vegetation

20. TYPES OF DROUGHT BASED ON CROP
GROWTH STAGE
• Transient Drought
• Occasionally drought occur at any growth stage
• It occur for short period of time
• Plant have ability to recover after availablity of water to plant / irrigation
• Semi- arid areas
• Terminal Drought
• Drought stress at lateral stages of growth called terminal drought
• Negatively affect the grain filling of crops

21. CONTINUE...
• Seasonal Drought
• Unavailbilty of water for economic crop production
• Insufficient availability / supply of rain water ( which cannot complete growth )
Effects Of Drought Stress
Emergence and germination
• Drought stress decrease speed & rate of germination
• Delayed imbibition
• Poor strach metabolism ( decrease conversion of starch into sugar ) Production of
Reactive Oxygen Species ( ROS ) O-2, OH- ,H2O2

22. CONTINUE...
Growth
• Combination of cell division,cell elongation and differentiation
• Drought stress-------›Loss of turgor ( imp for cell enlargement )
• Reduced meiosis ( imp for cell division )
Morphological growth
Physiological growth

24. EFFECTS OF DROUGHT STRESS
• Reduced cell expansion
• Reduced plant height
• Reduced leaf area
• Premature leaf scenesense
• Leaf rolling
• Wilting
• Yellowing of leaves

25. Drought stress
• hampers flowering and grain filling
• decreases yield & yield components
• poor source sink relationship

26. PHYSIOLOGICAL EFFECTS OF DROUGHT
Drought stress disturbs;
• Photosynthesis
• Respiration
• Plant nutrient relationship
• Plant water relation
Photosynthesis
• Direct effect
• Stomatal limitations
• Non stomatal limitation/ metabolic limitation
• Indirect effect
• Reduced Leaf area
• Premature leaf falling
• Leaf wilting

27. CONTINUE...
Physiology Effects of drought stress
Reduced leaf water potential Leads to
1. Reduction in Rubisco
2. Reduction in PEPcase & FBP
3. Enhance level of Rubisco inhibitor
4. Production of ROS
ROS react with different cellular organelles and cause cellular damage leads to reduced
carboxylation
Reduction in water potential increase ABA level leads to stomatal closure
Also reduced ATP production leads to reduced energy supply and reduced photosynthesis

29. EFFECT OF DROUGHT STRESS ON PLANT
WATER AND NUTRIENT RELATION
• Reduction in leaf water potential
• Relative water contents
• Transpiration
• Stomatal conductance
• Increase in canopy temperature
• Reduction in aquaporines ( protein facilitate intra cellular water movement )
• Reduced uptake, translocation, and utilisation of nutrients

30. CONTINUE...
Respiration ( over all decreases )
Drought stress leads to increase root respiration

31. DROUGHT STRESS IN PLANTS
Resistance:-
• It is ability of plant to immunize itself against particular stress factor is called resistance
Drought Tolerance:
• Ability of plant to grow well/ satisfactory and furnish better yield under water limited conditions
known as drought tolerance.
Drought Adaptation:-
• Modification in structure and function of plants that increase the chances of plant survival under
water limited conditions e.g leaf senescence to decrease water losses.
Drought Acclimation:-
• Ability of a plant to Adjust itself to new environmental conditions

32. CATEGORIES OF DROUGHT TOLERANCE
• Drought Escape.
• Drought Avoidance
• Drought survival
Drought Escape:-
It is the ability of the plant to shorten their life cycle in order to prevent from explosure to
drought stress.
Development plasticity:- Ability of plant to adjust their life cycle according to the extent
and duration of stress factors.

33. CONTINUE...
Drought Avoidance:-
It is ability of plant to sustain to maintain the leaf water content in order to prevent the negative effect of drought
stress.
By enhancing water uptake
• Through extensive root system
• Increased hydrological conductance
By reducing the loss of water
• Reduced leaf area
• Thicker leaves
• Leaf pubescence (Leaf hairs)
• Leaf senescence
• Leaf Rolling
Drought survival:-
It is the ability of plant to survive for long period of time under water limited conditions, e.g xerophyte

34. MORPHO- PHYSIOLOGICAL INDICATORS FOR DROUGHT
TOLERANCE
• Early maturity / short duration
• Developmental plasticity (life cycle may be extended)
• Stomatal closure
• Leaf rolling
• Leaf senescence
• Leaf hairs
• Extensive/ deep roots
• Changes in leaf angle
• Wax deposition on leaves
• Anti-oxidative defence system
• Osmotic adjustment ( sugar etc ) maintain osmotic balance
• Harmonal Balance, ABA, cytokinin

35. END