Stomata (singular, stoma), sometimes anglicised as stomates, which mean ‘mouths’ in Greek, do resemble tiny mouths.
Guard cells are two bean shaped cells that surround a stoma. Guard cells are specialized epidermal cells as they contain chloroplasts. They play an important role in gaseous exchange in and out of plant leaves by regulating the opening of pores known as a stoma.
Stomata are typically 20–50 μm long and occur at densities between 50 and 300 mm−2, and can often be found on stems, leaves, flowers and fruits, but not on roots.
Plants regulate water loss either by opening and closing their stomata or by varying their stomatal densities.
Gas exchange occurs when carbon dioxide molecules enter the leaves for photosynthesis and when excess oxygen molecules leave the leaves. The pores allow for water flow throughout plants by creating a lower water pressure at the leaves than at the roots.
A reduction in water absorption results in water stress, which reduces transpiration, causing stomatal closure and a reduction in photosynthesis. In combination, these effects contribute to reduced shoot growth.
Insect and disease damage can interfere with leaf physiology, stomatal function, and the resulting transpiration rate that increases leaf temperature.
Stomata in tree leaves
