What occurs when water molecules stick to one another, aiding in their upward movement in plants?

Cohesion refers to the attractive forces between water molecules, which are due to hydrogen bonding. This property allows water molecules to stick together, creating a continuous column of water within the plant's vascular system, particularly in the xylem. As water evaporates from the leaves through stomata, it creates a negative pressure that pulls more water upward from the roots. This interconnectedness of water molecules is critical for the process of transpiration, where water moves against gravity, enabling plants to efficiently transport nutrients and maintain hydration throughout their structure.

While adhesion occurs when water molecules stick to other surfaces (like plant cell walls), and capillarity involves the combination of both adhesion and cohesion to draw water up through narrow spaces, it is the cohesive forces among the water molecules themselves that primarily enable the upward movement within the plant system. Evaporation, while relevant to the process of transpiration, is more about the transition of water from liquid to gas and does not directly describe the interaction between the water molecules themselves.