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Plant Physiology: Photosynthesis and Respiration
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Abscisic acid causes
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A
rapid movement of K+ out of the guard cells
💡 Explanation:
Abscisic acid (ABA) acts as a stress hormone that triggers stomatal closure. It does this by inhibiting H+ pumps and promoting the rapid efflux of K+ ions from guard cells, which leads to water loss and turgor reduction.