Transpiration is the process of water loss from plants through evaporation. It occurs mainly through the stomata, which are small pores on the leaf surface that allow gas exchange. Plants take in more water than they need for growth and metabolism, and transpire the excess water to regulate their temperature and access carbon dioxide. Transpiration also helps maintain the moisture balance in the environment and influences the water cycle. Transpiration accounts for about 10% of the water vapor in the atmosphere.