Transpiration is the process of water moving from the roots of plants moving through their stems and branches and then being excreted in the form of water vapor through pores (stomata) in the surfaces of their leaves, flowers and other above-ground parts. The rate of transpiration is controlled by the size of the stomata openings and is also influenced by the humidity, temperature, wind, sunlight and availability of water in the soil. The stomata open during the day in the presence of sunlight and close at night in its absence.
In addition to removing excess water, transpiration also allows the movement of nutrients dissolved in the water to the shoots, cools the plants while exposed to direct sunlight, and makes it easier for the leaves to absorb carbon dioxide. This gas is absorbed through the stomata while they are open to release water vapor.
Transpiration by plants can be of major importance for other organisms within a habitat because it helps maintain a specific moisture level there. It also plays a fundamental role in the water cycle and thus in the biosphere as a whole because it is one of the major sources of water vapor in the atmosphere.