The loss of water vapour by plants to the atmosphere. It occurs mainly from the leaves through pores (stomata) whose primary function is gas exchange. The water is replaced by a continuous column of water (and dissolved nutrients) moving upwards from the roots within the xylem vessels. The flow of this column of water is known as the transpiration stream, which is maintained by root pressure and a combination of cohesive and adhesive forces in the xylem vessels according to the cohesion-tension theory (see cohesion). See also potometer.
Subjects: Biological Sciences.