Soil water, absorbed by plants, is called

Question

Question

This question was previously asked in

UP TGT Biology 2016 Official Paper

Answer 1

Key Points

The given terms are in relation to the various forms in which water is available in the soil.
Hollard – is the total water content present in the soil.
Chresard is the amount of water available for the plants in the soil.
It is also called growth water or available water.
It contains about 75% of capillary water because plant roots cannot absorb water from capillaries less than 0.2µm in diameter.
Echard – is the part of Hollard that is unavailable for the plants. It consists of hygroscopic water, chemically combined water, water vapour and 25% of capillary water.

Additional Information

The soil water can be of the following types:

Gravitational water – reaches the water table after rainfall due to gravity. It is not available to plants but can be obtained mechanically by pumps, etc.
Hygroscopic water – is the thin film of water that is held together by soil particles and is also not available for plants.
Chemically combined water – refers to the water molecules bound to chemical substances present in the soil.
Capillary water – is present in the narrow pores between the soil particles and is the only available water for plant absorption.