Mechanism of opening and closing of stomata pdf
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- Stomatal Mechanism in Plant Cells | Botany
- The mechanism of stomatal action
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Since the late s, researchers have observed that starch in the chloroplasts of the guard cells breaks down during the day and accumulates in the dark. Based on this, carbohydrates have historically been regarded as the primary osmotica modulating stomatal opening. However, the discovery of an important role for potassium uptake has led to the replacement of that starch-sugar hypothesis. However, questions remain concerning photoreceptors, and the functioning of guard cell chloroplasts is still disputed. Coincidentally, some recent study results have again suggested that sucrose may play a major role in guard cell osmoregulation, thus supporting the original theory of starch-sugar involvement.
Stomatal Mechanism in Plant Cells | Botany
The mechanism of stomatal action
A stoma is a minute pore on the epidermis of aerial parts of plants through which exchange of gases and transpiration takes place. Each guard cell is a modified epidermal cell showing a prominent nucleus, cytoplasm and plastids. The wall of the guard cell is differentially thickened. The inner wall of each guard cell facing the stoma is concave and is thick and rigid. The outer wall is convex and is thin and elastic. Opening and closing of stomata takes place due to changes in turgor of guard cells. Generally stomata are open during the day and close at night.
Recent reviews have denied the applicability of the classical theory of stomatal movement. The newer explanations are shown to be incorrect, and the major objections to the classical theory invalid. Nevertheless, the classical theory needs to be modified. Two predictions of this modified classical theory were vindicated. This is a preview of subscription content, access via your institution. Rent this article via DeepDyve.
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The stomata are very minute apertures, usually found on the epidermis of the leaves. Each stoma is surrounded by two kidney-shaped special epidermal cells, known as guard cells. The stomata may be found in all the aerial parts of the plant. They are never found on its roots. The epidermal cells surrounding the guard cells of the stoma are known as accessory or subsidiary cells.