Abscisic Acid: The Plant Stress Hormone — NEET Biology
📚 Practice ConceptWhy is abscisic acid also known as stress hormone?
Which of the following statements, linking a Plant Growth Regulator with its effect/application, are NOT correct? S1: Auxin – Initiates rooting in stem cuttings and prevents fruit drop at early stages. S2: Ethylene – Enhances the respiration rate during fruit ripening, a phenomenon called respiratory climactic. S3: Gibberellins – Delay senescence, allowing fruits to be left on the tree longer for extended market periods. S4: Cytokinins – Promote stomatal closure and increase plant tolerance to various stresses. S5: Abscisic acid (ABA) – Is primarily known for promoting rapid cell division in root apices and developing shoot buds. S6: Auxin – Applied to make weed-free lawns as 2,4-D kills dicotyledonous weeds without affecting mature monocotyledonous plants.
View solution & NCERT explanation
Correct answer: B — S4 and S5 only
This question tests the ability to distinguish between the various physiological effects and applications of different Plant Growth Regulators (PGRs). Let's evaluate each statement: S1: Auxins help to initiate rooting in stem cuttings and prevent fruit and leaf drop at early stages. This statement is correct. S2: Ethylene enhances the respiration rate during the ripening of fruits, which is called respiratory climactic. This statement is correct. S3: Gibberellins delay senescence. Thus, fruits can be left on the tree longer to extend the market period. This statement is correct. S4: Abscisic acid (ABA), not cytokinins, stimulates the closure of stomata and increases the tolerance of plants to various kinds of stresses, earning it the name 'stress hormone'. This statement is NOT correct. S5: Cytokinins, not abscisic acid (ABA), are synthesised in regions where rapid cell division occurs, such as root apices and developing shoot buds. ABA acts as a general plant growth inhibitor. This statement is NOT correct. S6: 2,4-D, a synthetic auxin, is widely used as a herbicide to kill dicotyledonous weeds without affecting mature monocotyledonous plants, thus used for weed-free lawns. This statement is correct. Therefore, statements S4 and S5 are NOT correct. Option B correctly identifies the incorrect statements. Options A, C, and D incorrectly categorize the statements. The anchor concept is the differentiation of physiological roles and applications among various plant growth regulators.
What does NCERT say about Why abscisic acid also?
Has this concept appeared in NEET?
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Through deep analysis of NEET and NTA, 176 of the 180 ReNEET 2026 (June 21) questions were already in the MedicNEET question bank before the exam.
176/180MedicNEET's Biology question bank is built from the same NCERT lines NTA picks repeatedly. Not random MCQs — questions crafted exactly like NTA crafts them.