Which term describes the soil moisture at which plants can no longer transpire effectively?

The term that describes the soil moisture at which plants can no longer transpire effectively is "Permanent Wilting Point." At this moisture level, the water availability in the soil has decreased to the point where plants cannot extract enough water to meet their physiological needs. As a result, they begin to wilt and will eventually die if the moisture is not replenished.

Understanding this concept is crucial because the Permanent Wilting Point signifies a critical threshold for plant health. Below this level, the tension that plant roots must exert to access water becomes so high that it surpasses their ability to absorb it, leading to a permanent state of wilting. This concept highlights the importance of sustainable irrigation and soil management practices to maintain adequate moisture levels for healthy plant growth.

Field Capacity refers to the maximum amount of water the soil can hold after excess water has drained, while Available Water Capacity indicates the range of water that plants can use. Soil Saturation Point describes a condition where all soil pores are filled with water, which also does not support effective transpiration for plants. Therefore, recognizing the differences among these terms helps in understanding key aspects of soil moisture management in horticulture.