General Science • BiologyMedium
Which phytohormone mediates stomatal closure during periods of severe water stress by triggering rapid efflux of potassium ions from guard cells?
A. Indole-3-acetic acid
B. Gibberellic acid
C. Abscisic acid✓ Correct Answer
D. Cytokinin
💡 Solution & Explanation
Abscisic acid accumulates rapidly in plant tissues under drought conditions and induces stomatal closure by promoting the outward flux of potassium ions and anions from guard cells, lowering turgor pressure. Indole-3-acetic acid promotes cell elongation and apical dominance rather than drought responses. Gibberellic acid stimulates stem elongation and seed germination by breaking dormancy. Cytokinins drive cell division and delay leaf senescence across vascular plants.
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