Translocation and Absorption of water by sohail

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