UPSC CAPF (AC) 2026 Paper I · Question 100

Question 100 of the UPSC CAPF (AC) 2026 Paper I (19 July 2026). Try it first, then open the answer and explanation.

1. CAPF 2026 · P-I · Q100 · General Science · Biology

   Which one of the following plant hormones promotes stomatal closure during drought stress?

   1. Auxin
   2. Cytokinin
   3. Gibberellin
   4. Abscisic acid

   निम्नलिखित में से कौन-सा पादप हार्मोन जलाभाव दबाव (drought stress) के दौरान रंध्र के बंद होने (stomatal closure) को बढ़ावा देता है?

   1. ऑक्सिन
   2. साइटोकाइनिन
   3. जिबरेलिन
   4. ऐब्सिसिक ऐसिड
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   Answer: (4) Abscisic acid

   उत्तर: (4) ऐब्सिसिक ऐसिड

   Abscisic acid (ABA), the "stress hormone", accumulates in leaves when water is scarce and makes the guard cells lose K+ ions and water, so the stomata close and water loss by transpiration is reduced. Auxin, cytokinin and gibberellin are growth-promoting hormones; cytokinins in fact tend to keep stomata open.

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