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In botany, a stoma (pl.: stomata, from Greek στόμα, "mouth"), also called a stomate (pl.: stomates), is a pore found in the epidermis of leaves, stems, and other organs, that controls the rate of gas exchange between the internal air spaces of the leaf and the atmosphere.
During the development of plant leaves, the specialized guard cells differentiate from "guard mother cells". [ 43 ] [ 44 ] The density of the stomatal pores in leaves is regulated by environmental signals, including increasing atmospheric CO 2 concentration, which reduces the density of stomatal pores in the surface of leaves in many plant ...
The stomata complex regulates the exchange of gases and water vapor between the outside air and the interior of the leaf. Typically, the stomata are more numerous over the abaxial (lower) epidermis of the leaf than the (adaxial) upper epidermis. An exception is floating leaves where most or all stomata are on the upper surface.
Stomatal conductance, usually measured in mmol m −2 s −1 by a porometer, estimates the rate of gas exchange (i.e., carbon dioxide uptake) and transpiration (i.e., water loss as water vapor) through the leaf stomata as determined by the degree of stomatal aperture (and therefore the physical resistances to the movement of gases between the air and the interior of the leaf).
The extinct arboreal plants of the genera Lepidodendron and Sigillaria were the first to have distinct aeration structures that rendered these modifications. "Parichnoi" (singular: parichnos) are canal-like structures that, in association with foliar traces of the stem, connected the stem's outer and middle cortex to the mesophyll of the leaf.
As an aquatic plant with leaves that rest on the water's surface, the genus Nelumbo is characterized by its concentration of stomata on the upper epidermis of its leaves, unlike most other plants which concentrate their stomata on the lower epidermis, underneath the leaf. [5]
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Leaf expansion is a process by which plants make efficient use of the space around them by causing their leaves to enlarge, or wither. This process enables a plant to maximize its own biomass, whether it be due to increased surface area; which enables more sunlight to be absorbed by chloroplasts, driving the rate of photosynthesis upward, or it enables more stomata to be created on the leaf ...