| Soil water |
Role of water in forest management…………………………………………
· Assumes an unusually important place because a high % of lands that is either too wet or too dry for agricultural use.
· The soil moisture largely controls the type of tree that effects distribution of forests throughout water.
· Soil with abundant nutrients but with no water is less suites for forest growth in comparison to soil with poor nutrients but with adequate water.
· Water is essential to the proper functioning of most soil & plant process. Water directly or indirectly affects the metabolic process of plants. It is a source of Hydrogen as a moderator of sol temperature & aeration & diluter of toxic substances.
Soil moisture contents…………………………………………………….
1) Maximum water holding capacity:
It is the state of which both capillary & non-capillary pore spaces are filled with water.
The water at this point is known as free water / drainage water / gravitational water.
Nutrient elements leached with this water when they drain downwards due to gravity.
This condition is not suitable for plant.
2) Field capacity:
· Water remains in capillary pore spaces & around soil particles by forces of cohesion & adhesion after gravitation.
· The water at this point is capillary water.
· It is an excellent concept of expressing the upper limit of plant available soil moisture.
· Water in soil solution remains at a pressure of 
rd atmospheric pressure.
3) Wilting point:
· This is the point which plants started wilting during dry & night, even when water is added to soil.
· It is the lower limit of plant available soil moisture.
· Water held at a pressure of atm / 1.5 mpa/1500 kpa.
4) Hygroscopic co-efficient:
· Water is retained very firmly as a thin layer around individual soil particles.
· Water is non liquid & moves primarily in the vapor form.
· Water is not available to higher plants.
· It is usually determined by exposing a thin layer of dry soil to a saturated atmosphere for 24 hours.
· Water held a pressure of 31 atm/3.1 mpa/3100kpa.
Role of water in plants…………………………………………….
1. Structural components: 90%-95% of total weight of a plant cell built up by water.
2. Temperature control: 95% of water in tropical plants is used in temperature control within plant body.
3. Maintaining turgidity: water maintains turgidity of plant cell which in turns results in the elongation cells & growth of plants.
4. Opening up stomata: the guard cells around the stomata swell up by absorbing coater & thus stomata opens.
5. Transportations: water is a medium of transportation of raw materials from root to leaves & manufactured food from leaves to different plant parts.
6. As a solvent: water acts as a universal solvents by saluting plant materials & dilute toxic substances.
7. Medium of chemical reaction: water acts as a medium of various chemical reactions within plants.
8. In hydrolysis: Hydrolysis is the process of addition of water which is used mainly in the conversion of carbohydrates or organic acids.
9. In photosynthesis: water is an important raw material of plant food manufacturing through photosynthesis.
10. In transpirations: water is pumped out from the plants through transpiration which in turns help water uptake by plants. Thus water balance within plant is maintained through transpiration.
11. In absorption of mineral salts: water generally converts into H+ & OH- ions during mineral salts absorption. These ions are exchanged with available nutrient elements. Such as K+, Na+, etc.
12. In germination of seeds: water increases rate of seed respiration which favors seed germination. Without water no germination is possible. Water acts in brisling seed dormancy as hard seed coats soften swallowing water through imbibitions.
13. In vacuoles of cell: water in vacuoles of cell maintains cell turgidity.
14. For action of protoplasm: water is essential for protoplasm action. Without water protoplasm remains inactive or even died.
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| Prepared by Rasel 23 |
