What phenomenon explains how water can move upward through plant roots?

The movement of water upward through plant roots is primarily explained by capillary action. Capillary action occurs due to the combination of cohesive forces (the attraction between water molecules) and adhesive forces (the attraction between water molecules and the surrounding materials, such as the cell walls of plant tissues).

In plants, water is absorbed by the roots and travels upward through thin tubes called xylem vessels. The properties of capillary action allow water to move against the force of gravity. The water molecules adhere to the walls of the xylem, while also pulling on other water molecules through cohesion to create a continuous column of water. This process is vital for transporting nutrients and maintaining hydration in the plant, showcasing the remarkable ability of plants to transport water efficiently from the roots to other parts like leaves and stems.

Other options, like osmosis, surface tension, and diffusion, describe other processes related to water movement, but they do not specifically account for the upward movement of water through the xylem in plants, which is effectively driven by capillary action.