In botany, a stoma (plural stomata) (occasionally called a stomate, plural stomates) (from Greek stóma, "mouth") is a pore, found in the epidermis of leaves, stems and other organs that is used to control gas exchange. The pore is bordered by a pair of specialized parenchyma cells known as guard cells that are responsible for regulating the size of the opening. The term is also used collectively to refer to an entire stomatal complex, both the pore itself and its accompanying guard cells. Air containing carbon dioxide and oxygen enters the plant through these openings and is used in photosynthesis in the mesophyll cells (parenchyma cells with chloroplasts) and respiration, respectively. Oxygen produced as a by-product of photosynthesis diffuses out to the atmosphere through these same openings. Also, water vapor is released into the atmosphere through these pores in a process called transpiration.

Some information in this copy may have been obtained from the online resource: Wikipedia: The Free Encyclopedia.

Learn more: http://en.wikipedia.org/wiki/Stoma