(redirected from Stomates)
Also found in: Dictionary, Thesaurus, Medical.


1. Botany an epidermal pore, present in large numbers in plant leaves, that controls the passage of gases into and out of a plant
2. Zoology anatomy a mouth or mouthlike part
3. Surgery an artificial opening made in a tubular organ, esp the colon or ileum



a slitlike opening in the epidermis of aboveground organs of plants. The stoma is bordered by two guard cells, which are usually bean-shaped. The walls of the guard cells that face the stoma are thick, while the opposite walls are thin. The stoma leads to a large intercellular space, the substomatal cavity. The stoma is often surrounded by two or more cells that differ in shape from ordinary epidermal cells.

Stomata are found in the epidermis of all aboveground parts of the plant containing chlorophyll but are especially numerous in leaf epidermis (100–300 per sq mm). They regulate the exchange of gas and water vapor between the atmosphere and the cells of the plant by increasing and decreasing in width. Stomatal movement is effected by changes in the turgor of the guard cells. When turgor is increased, the thin parts of their walls stretch and are drawn away from the stoma. The walls that face the stoma are distended in the same direction, and the stoma opens. When the turgor of the guard cells decreases, the stoma closes. Change in the turgor of the guard cells occurs as a result of reversible conversion of starch, which is osmotically inactive, into osmotically active sugars. However, according to some data, potassium ions play an important, possibly leading, role in regulating the turgor of the guard cells. Scientists are currently investigating these data with the intention of formulating a new hypothesis of the mechanism of stomatal movement.

At night, the stomata of most plants are closed, and gas exchange and transpiration are minimal. During the day, when the weather is fair, the stomata are open. Carbon dioxide gas readily enters the internal tissues of the plant, and oxygen formed as a result of photosynthesis is released with water vapor into the atmosphere.



A small opening or pore in a surface.
One of the minute openings in the epidermis of higher plants which are regulated by guard cells and through which gases and water vapor are exchanged between internal spaces and the external atmosphere.
References in periodicals archive ?
Plants exchange gases in photosynthesis and respiration through pores called stomates and lenticels.
1998), indicated that it is necessary to maintain high relative humidity and low light intensity until plants have adequately developed stomates and cuticle.
An interesting example of all three patterns is the occurrence of clustered stomates on leaves in some Begonia cultivars (Figure 1).
A similar situation occurs al Antifreeze Pond, with stomates and macrofossils indicating local spruce, but low (< 5%) pollen frequencies suggesting otherwise (Vermaire, 2005).
5 mm in thickness, have stomates on both leaf surfaces, and have undifferentiated parenchyma (Rodman 1974).
The partial closing of the stomates with a doubling of C|O.
For example, under drought conditions, ABA levels in leaves increase, and exogenous application of ABA induces closure of stomates, the pores in leaves through which gases and water pass.
complex because of the presence of stomates, trichomes, and veins, as
Anatomical studies showed differences in size and shapes of prickles, short cells, silica bodies, micro hairs with basal and distal cells, hooks, stomates and long cells of Paniceae species.
Others obtain entry into plants by insect vectors or can simply enter through stomates.
These plants should do better under hot, dry conditions because they can close the stomates on their leaves during the day, thereby reducing water use.
Other plant characteristics such as stomates and trichomes could also play a role in disease resistance or susceptibility.