The correct answer is option 'C) Permanent Wilting Point'.

Permanent Wilting Point:
The Permanent Wilting Point (PWP) is the lowest amount of water in the soil that a plant requires to maintain its turgidity. It is the point at which the soil moisture content is so low that the plant cannot extract enough water from the soil, leading to permanent wilting and death of the plant.

Factors affecting Permanent Wilting Point:
Several factors influence the permanent wilting point of a soil, including:
1. Soil Texture: Soils with finer textures, such as clay, have a higher water-holding capacity and a lower permanent wilting point compared to sandy soils. This is because the small particles in clay soils can hold onto water more tightly.
2. Organic Matter Content: Soils with higher organic matter content have a higher water-holding capacity and a lower permanent wilting point. Organic matter acts as a sponge, holding onto water and making it more available to plants.
3. Climate: In arid and semiarid regions with low rainfall, the permanent wilting point is generally higher compared to humid regions with higher rainfall. This is because plants in arid regions have adapted to survive with limited water availability.
4. Plant Species: Different plant species have different water requirements. Some plants have deeper root systems that can access water at lower soil moisture levels, while others have shallow root systems and are more sensitive to soil moisture deficits.

Importance of Permanent Wilting Point:
Understanding the permanent wilting point is crucial for agricultural practices and water management. It helps in determining the irrigation needs of crops and preventing water stress. By maintaining soil moisture above the permanent wilting point, farmers can ensure optimal plant growth and yield.

Conclusion:
The permanent wilting point is the lowest amount of water in the soil that a plant requires to maintain its turgidity. It depends on factors such as soil texture, organic matter content, climate, and plant species. Understanding the permanent wilting point is essential for effective water management in agriculture.