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guard cell


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A specialized type of plant epidermal cell (see epidermis), 2 of which surround each stoma. Changes in their turgidity cause stomatal opening and closing. This procees is not fully understood but includes: (a) the effects of the overall water potential of the plant on the stomata; (b) a feedback mechanism, whereby when water is plentiful abscisic acid is formed and stomata open and when water is scarce abscisic acid is not released and the stomata close; (c) low carbon dioxide levels promote stomatal opening; (d) except in CAM plants, stomata normally open in light and close in darkness; (e) generally, an increase in temperature tends to increase stomatal opening.

(a) the effects of the overall water potential of the plant on the stomata; (b) a feedback mechanism, whereby when water is plentiful abscisic acid is formed and stomata open and when water is scarce abscisic acid is not released and the stomata close; (c) low carbon dioxide levels promote stomatal opening; (d) except in CAM plants, stomata normally open in light and close in darkness; (e) generally, an increase in temperature tends to increase stomatal opening.

Gondwana

Subjects: Plant Sciences and Forestry.


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