What is the release of water vapor from plants called?

The release of water vapor from plants is called transpiration. Most transpiration occurs through tiny pores called stomata, usually found on the surfaces of leaves. Water absorbed by the roots travels upward through xylem vessels and eventually evaporates from moist internal leaf surfaces before diffusing into the atmosphere.

Transpiration is not simply a waste process. It helps create a continuous pull that moves water and dissolved mineral nutrients from roots toward stems and leaves. It also cools plant tissues, much like sweating cools the human body. Sunlight, temperature, humidity, wind, and the opening or closing of stomata all influence its rate.

A common mix-up is confusing transpiration with evaporation. Evaporation is the general change of liquid water into vapor, while transpiration specifically describes water vapor leaving living plants. Guttation is different again: it is the release of liquid water droplets, often from leaf edges, through specialized structures called hydathodes.