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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 ?
Stomal opening and closure motions increase the photosynthesis rates and thus increase the yield.
A stomal infection was considered when there was a frank purulent discharge from the source with surrounding erythema of [greater than or equal to]1cm.
Our aim in performing radical cystectomy and panniculectomy concomitantly was to improve exposure to the pelvic organs, facilitate maturation of the ileal conduit, and potentially improve stomal outcomes.
It may also establish a self-cleaning low energy surface that (along with the hygiene protocol) limits biofilm adhesion and related superficial stomal infection.
In another international study stomal granulation was observed as most frequent late complication in consis- tence on our observation.
The usual stomal diameter should be between 5 and 10 mm and show adequate emptying.
As stomal complications are more common with transverse colostomy, sigmoid loop colostomy should be per-formed in ARM and short segment HD.
Short term complications including haemorrhage, surgical emphysema, cardiac arrest and stomal infection were noted in both groups.
Clinically, only one patient who was diabetic had reappearance of gangrene at the stomal site of the small bowel (no.
Ortotopik diversiyonlarm ve kontinan kataterize edilebilen rezervuarlarm hasta acisindan daha kabul edilebilir sekilde gelistirilmis olmasina ragmen; gerek zorunlu stomal diversiyonlar, gerekse bu ameliyatin yapilamayacagi morbiditeleri yuksek veya organmi kaybetmek istemeyen hastalar, doktorlari mesane koruyucu tedavilerin (MKT) gelis-tirilmesine zorlamislardir.
with a focus on fostering high standards of stomal therapy, promoting professional and educational advancement of ET practitioners, and promoting optimal care and rehabilitation for ostomates.
Australian Association of Stomal Therapy Nurses Inc.