Plants breathe through their stomata, little openings that allow transpiration, which is the outward passage of water vapor along with carbon dioxide. This vapor then evaporates into the air as part of the process of photosynthesis.
We can see the history of the word transpiration when we break it down into trans, a Latin noun which means "across," and spiration, which comes from the Latin verb spīrāre, meaning "to breathe." The tion suffix adds the meaning "the act of," so we can see transpiration is, literally, "the act of breathing across," which clearly identifies vapor emission from plant leaves. Transpiration is vital to the earth’s ecology, and is being reduced by our decimation of the forests.
