DENDROLOGY

Detailed explanation-1: -Permanent wilting point is considered as the lower limit of available soil moisture. At this stage, water is held tightly by the soil particles that the plant roots can no longer obtain enough water to satisfy the transpiration requirements; and remain wilted unless the moisture is replenished.

Detailed explanation-2: -The soil is considered to be at permanent wilting point when the water potential in the soil is at or below-1.5 MPa, so the permanent wilting point is the water content of the soil at-1.5 MPa water potential.

Detailed explanation-3: -The point at which matric forces hold water too tightly for plant extraction (-1.5 MPa) is termed the permanent wilting point.

Detailed explanation-4: -Hygroscopic water Hygroscopic water is the water which is adsorbed by the soil particles. It forms a thin film over the soil particles and is not available to the plants.