Plants take in carbon dioxide, exhale oxygen and water vapor.
Water being taken into and evaporating from plants, is called transpiration. Transpiration also includes the taking in of carbon dioxide, which is essential for photosynthesis.
Moisture in The Soil
The water that plants take in comes from moisture in the soil. Roots take in this water, which also contains dissolved minerals, through osmosis. These minerals are necessary for the plant to produce food, to reproduce, to store food, and to continue to survive. The water also helps keep the plant turgit, helping it to stay upright.
Xylem
The mineral-rich water solution moves up the plant through the xylem. It is taken up into the leaves where, mixed with carbon dioxide and sunlight, it creates food for the plant through the process of photosynthesis.
Stomates
Stomates are small pores, usually on the underside of leaves, which take in carbon dioxide. Transpiration keels the plant healthy, helps produce oxygen which is expelled through those same stomates.
Transpiration Rate
The rate of transpiration is directly proportional to how large the stomates are open. The stomates open and close through the action of two guard cells, which expand and deflate in accordance with the plant’s need for carbon dioxide intake. Since sunlight is necessary for photosynthesis, and no photosynthesis can take place at night, most plants close their stomates to some extent during the night. But plants do expel oxygen through these stomates at night.
Cloudiness, temperature, humidity, wind and a number of other factors can influence the opening and closing of stomates.
