Correct Option: C. Capillary Water Explanation of the Correct Answer: Capillary water is the water that is held in the soil's micropores and is available for plant uptake. It is the most significant source of water for plants because it is retained in the soil after gravitational water has drained away. Here’s a step-by-step breakdown of why capillary water is the correct answer:

1. Understanding Soil Water Types:
2. Gravitational Water: This is the water that moves through the soil due to gravity. It is not retained in the soil and drains away quickly, typically after heavy rainfall. Plants cannot use this water effectively because it moves too quickly through the soil.
3. Hygroscopic Water: This is the water that is tightly bound to soil particles and is not available to plants. It forms a thin film around soil particles and cannot be absorbed by plant roots.
4. Capillary Water: This water occupies the spaces between soil particles and is held by surface tension. It is accessible to plants and is the primary source of water for their growth and development.
5. Surface Water: This refers to water found on the surface of the soil, such as puddles or water bodies. While it can be a source of water, it is not directly absorbed by plant roots in the same way as capillary water.
6. Why Capillary Water is Essential:
7. Capillary water is crucial for plant health because it is the form of water that plants can absorb through their roots. The roots have specialized structures that allow them to take up this water efficiently.
8. It provides the necessary moisture for various physiological processes, including photosynthesis, nutrient transport, and cellular functions.
9. Illustration of Water Movement:
10. Imagine a sponge soaking up water. The sponge represents the soil, and the water it absorbs represents capillary water. Just as the sponge can hold onto water and release it slowly, the soil retains capillary water, making it available to plants over time.

Explanation of Incorrect Options:

• A. Gravitational Water:
• This option is incorrect because gravitational water drains away quickly and is not retained in the soil. Plants cannot rely on this water source for their needs, as it does not remain in the root zone for absorption.
• B. Hygroscopic Water:
• Hygroscopic water is not available to plants because it is tightly bound to soil particles. Plants cannot extract this water, making it an unsuitable option for their water source.
• D. Surface Water:
• While surface water can be a source of moisture, it is not the primary source for plants. Surface water can evaporate quickly or be lost to runoff, and it does not provide the sustained moisture that capillary water does.

Revision Summary:

• Capillary water is the primary source of water for plants, held in soil micropores and available for uptake.
• Gravitational water drains quickly and is not retained, making it unavailable for plant use.
• Hygroscopic water is tightly bound to soil particles and cannot be absorbed by plants.
• Surface water is not a reliable source for plants as it can evaporate or runoff quickly.

Understanding these concepts is crucial for effective agricultural practices and ensuring optimal plant growth.