How is water primarily used by plants in the soil?

Plants primarily utilize capillary water in the soil for several reasons related to its availability and accessibility. Capillary water occupies the small spaces between soil particles and forms a thin film around them, which allows it to be easily absorbed by plant roots through a process called osmosis. This type of water is crucial for various physiological processes, including photosynthesis, nutrient transport, and cellular hydration, supporting overall plant health and growth.

Gravitational water, while also available in the soil, tends to drain quickly away from the root zone due to gravitational forces and is not usually held in the soil for an extended period. Hygroscopic water, on the other hand, is tightly bound to soil particles and is not accessible to plants because it cannot be taken up by roots. Surface water typically refers to water found in bodies of water such as ponds or rivers, and although it plays a role in the water cycle, it is not the primary form of water exploited by plants in the soil for their needs. Thus, capillary water serves as the main source of moisture for plants to thrive.