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Q.
Abscisic acid causes
AIPMTAIPMT 1991Plant Growth and Development
Solution:
Absisic acid is a hormone which produced during adverse environmental condition. It also causes the closure of stomata under conditions of water stress as also under high concentration of CO2, in the guard cells. Abscisic acid inhibits the K+ uptake by guard cells and promotes the leakage of malic acid. It results in reduction of osmotically active solutes so that the guard cells become flaccid and stomata get closed.