Permanent wilting point moisture content for a crop represents the hygroscopic water.

Explanation:

The permanent wilting point (PWP) is the moisture content in the soil at which plants can no longer extract water effectively, leading to permanent wilting and ultimately death. It is an important parameter for understanding the water availability to plants and is influenced by various factors such as soil type, plant species, and climate.

Hygroscopic Water:
Hygroscopic water is the water held tightly by soil particles due to the forces of adhesion and cohesion. It is the water that is strongly attracted to the soil particles and is not available for plant uptake. It is held at extremely low tensions and cannot be extracted by plant roots. This water is typically found at low moisture content levels in the soil.

Field Capacity:
Field capacity refers to the maximum amount of water that can be retained in the soil after excess water has drained away and the soil has reached equilibrium. At field capacity, the soil is saturated with water, and excess water moves downward due to gravity. This moisture level is considered optimal for plant growth as it provides a good balance of air and water in the soil.

Capillary Water:
Capillary water refers to the water held in the soil against the force of gravity in the capillary pores. This water is available for plant uptake as it is held at a tension that can be overcome by plant roots. Capillary water is important for plant growth and is typically found at intermediate moisture content levels in the soil.

Conclusion:
The permanent wilting point moisture content for a crop represents the hygroscopic water, which is the water tightly held by soil particles and not available for plant uptake. Understanding the permanent wilting point is crucial for determining the water availability to plants and managing irrigation practices effectively. It helps in preventing water stress and ensuring optimal plant growth and yield.