درسی

Soil Moisture

Water is found is several forms in the soil. The most transient of these forms is free water.after a rain some of water spees downward through the soil by the force of gravity;it ofen joins to cavern water table.

Free water which does not drain often harmful to plant growth. There force the removal of excess water by means of a drainage system is an essential agricultural operation.

When all free water has been drained form a soil the soil is said to be at field capacity.

When a soil is at field capacity, most of the water present in it is in the form of capacity water . this form of soil moisture is most useful to plants.capacity water adheres to soil particles by means of surface tension;it alos fills the smaller spaces among soil particles.

Free water and capillary water are both available for the use of plant. But the third main form of soil moisture is unavailable.

This form which is called hygroscopic moisture consists of permanent soil water is very closely contact with soil particles.

 

 

Transient               seep            cavern                   gravity

Capacity               capillary       adhere                   Tension                 hygroscopic

          particle

 

 

  

 

The Use Of Water By Plant

The water wich a plant takes up from the soil plays an essential role is nearly all of its activities. The water is the liquid in which soilds must be dissolred before being trancported within plant.

Water is a raw material in photosynthesis and an important factor in the growth of cells.

Water is absorbed by way of root hairs. A root hairs is simply an elongated part of a cell in the epidermis of a root .

The root hairs grow into small soil capillaries and spaces between soil particles where they contact water.

The most important factor in obtaiting a new supply of water is the growth of roots into new soil.

Transpiration

loss of water from plant known as transpiration is controlled by stomata cells. The stomata behave normally as long as the plant has readily available moisture and as the cells remain turgid.but has not available moisture the stomata are usually closed.

 

Partially                 stomata                 essential                liquid

Dissolve                root hairs               capillaries              transpiration

Moisture                photosynthesis