Translocation and Absorption of water Absorption of water Functions of water Active and Passive absorption Factors affecting absorption of water Effective root zones Moisture extraction pattern Translocation

1. IN THE NAME OF ALLAH THE MOST
GRACIOUS AND THE MOST MERCIFUL

2. Translocation and Absorption
of water
Presented by:
Sohail Riaz
Presented to:
Ma’am Iqra Munir

3. Contents
 Absorption of water
 Functions of water
 Active and Passive absorption
 Factors affecting absorption of water
 Effective root zones
 Moisture extraction pattern
 Translocation

4. Absorption of water
 The absorption of water is essential for various
metabolic activities. Terrestrial plants get their water
supply from soil which serve as the sources of water
and (minerals).
 The way in which water enter into the roots from the
soil, particularly to the root xylem is called
“Mechanism of water absorption”.

5. Function of water
 Water is major component of the cell.
 Water is a solvent for the uptake and transport of the
material.
 Water is good medium for biochemical reactions.
 Water is a reactant in many biochemical
reactions.(photosynthesis)
 Offspring dispersal.

6. Cont……….
 Provide structural support via turgor
pressure.(leaves)
 It is a medium for transfer of plant gametes.(sperm
swim to egg)
 In water some aquatic plants shed pollen
underwater.
 Thermal buffer.
 Cell elongation and growth.

7. Active absorption
 Active absorption refers to the absorption of water
by roots with the help of ATP, generated by the
roots respiration: as the root cells actively take part
in the process, it is called Active absorption.

8. Active osmotic water
absorption
 This theory was given by Atkins (1916) and Preistley
(1923).
 According to this theory, the root cells behave as an
ideal osmotic pressure system through which water
moves up from the soil solution to the root xylem
along an increasing gradient of D.P.D.

9. Active non-osmotic water
absorption
 This theory was given by Thimann (1951) and Kramer
(1959)
 According to the theory, sometimes water is
absorbed against a concentration gradient. This
requires expenditure of metabolic energy released
from respiration of the root cells.

10. Passive absorption
 This mechanism is carried out without utilization of
metabolic energy.
 Only roots acts as organ of absorption.
 Sometimes it is called water absorption ‘through roots’.
 It occurs during daytime bi ecause stomata are open
daytime.
 The force for absorption of water is created at the leaf
end i.e transpiration pull.

11. Factor affecting absorption of
water
1.Physical factors:
 Soil water contents
 Soil temperature
 Soil aeration and flooding

12.  Soil water contents
 When the soil moisture decrease below the wilting
point, plant roots have to exert more pressure and
thus rate of absorption decreases.
 When soil is completely saturated with water, then
soil temperature and aeration is poor and this
condition also affects the absorption of water.

13.  Soil temperature
 In many plants, water absorption below a soil
temperature of 10*C is reduced sharply and 25*C soil
temperature uptake of water is slowed down.
 Temperature above 40*C does not support water
absorption and plants show signs of wilting.

14. Cont………..
A freezing temperature reduces water absorption
because of following causes:
 Decreased root growth
 Increased viscosity of water
 Increased resistance to movement of water into roots

15.  Soil aeration and flooding
Following are the possible reason of flood injury:
 Poor availability of oxygen and occurrence if higher
carbon dioxide around roots
 Accumulation of toxic substances either in the sub-
merged roots or around them
 Change in pattern of ion uptake resulting in the
accumulation of some toxic ions

16. 2.Atmospheric factors
 The amount of soil moisture that is available to the
plant is determine by the moisture characteristics of
the soil, the depth to which the plant roots extend
and the proliferation of the roots.
 Soil moisture characteristics, such as field capacity
and wilting percentage and peculiar to a soil and
are a function of the texture and organic matter.

17. Cont…….
 Water is an unsaturated soil moves very slowly and
only a distance of few cm.
 To utilize effectively the moisture in the soil roots
must continue to proliferate into unexploited zones
throughout the plants growth cycle.
 Transpiration is effective due to the different
atmospheric factors such as wind velocity, humidity,
sunlight etc.
 When temperature and wind velocity are more
sunlight for longer period and humidity are less,
under such conditions transpiration is more.

18. 3.Biological factors
 Under favorable soil water, potential soil ,aeration
and root system of the plants strongly influence the
uptake of water.
 Root growth is influence by water. When growth of
roots is more, uptake of water is also more.
 Other plant factors such as morphology of leaves,
stomatal mechanism and growth stage of the plant
influence the rate of transpiration.
 The increased rate of transpiration, more water
absorption.

19. Effective root zone
 Effective root zone is the depth from which the
roots of average mature plants are capable of
reducing soil moisture to the extant that it should
be replaced by irrigation.
 Root development of any crop varies widely with
the type of soil and other factors.

20. Moisture extraction pattren
 It shows the relative amount of moisture extracted
from different depths within the crop root zone.
 It is seen that about 40% of the total moisture used
is extracted from first quarter of the root zone, 30%
from the second, 20% from the third and only 10%
from the last quarter.

21. Translocation
 It is the movement of material from leaves to other
tissues throughout the plants.
 Plant produce carbohydrate in their leaves by
photosynthesis, but non-photosynthetic parts of the
plants also requires carbohydrates.
 Occurs in Phloem

22. Mechanism of translocation
 Munch Pressure flow hypothesis
 Sugar loaded into phloem
 increase in solute potential
 leads to increase in water uptake from xylem
 builds up hydrostatic pressure
 unloaded at sink

23. Source-sink relationships
 Bidirectional: up and down plant
 Is it in same cell, not clear
 Rate 30-150 cm/hr, slower than water

24. Source to Sink
 Proximity of source to sink is critical
 Sinks may change during life cycle
 Young leaves net import
 As mature become exporter
 Roots, shoots, tubers, fruits are strong sink

25. Thank you