Stoma

Definition - What does Stoma mean?

In botany, the stoma or stomate are pores or holes found in the epidermis of the aerial parts of plants such as the leaves, stems, and other plant organs. Also known as stomata or stomates (plural), these small pores are the structures that allow there to be gaseous exchanges between the plant’s cells and tissues and the atmosphere.

Stoma is always bordered by two guard cells, which are specialized parenchyma cells that regulate the aperture (the size of the opening) of the stoma based on the needs of the plant.

The complete structure of the stoma and guard cells is known as a stomatal complex. Found mainly on the lower epidermis of the leaves, the size of the pores vary between species, with lengths ranging from 10 to 80 µm and widths ranging from a few to 50 µm.

MaximumYield explains Stoma

Stoma play an important role in plants because air enters through these openings, carrying carbon dioxide and oxygen that are both used during photosynthesis and respiration. Oxygen, which is a byproduct of photosynthesis, diffuses out to the atmosphere through these same pores.

Additionally, transpiration, or the release of water vapor, occurs through the stomata in order to manage the concentration of water in the plant cells. For example, in dry environments with low water availability, stomata are very small so as not to allow much respiration and water to escape from the plant, whereas in water-abundant environments, stomata are wider, which allows for easy respiration without withholding water.

Stoma are present in the sporophyte generation of all land plant groups, except liverworts. In the leaves of dicotyledons, stoma are randomly scattered, while in the leaves of monocotyledons, they are organized into parallel rows.

Stoma are present in plant areas with easy access to air. Therefore, in plants with floating leaves, they might be found only on the upper epidermis. It is not uncommon for submerged leaves to not have stoma.

There are various types of stomata that are classed according to their size and structural layout, such as: coniferous stomata, gramineous, diacytic, paracytic, anisocytic, and anomocytic.

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