Biology · Plant Growth and Development · NEET
Auxin is MADE by the shoot tip and SUPPRESSES the side (axillary) buds, so the plant grows tall and less bushy. This suppression is apical dominance. Cytokinin does the OPPOSITE: it helps OVERCOME apical dominance so lateral buds grow. So in a match question, 'causes apical dominance' = auxin, but 'overcomes apical dominance' = cytokinin. NCERT (Ch 13): 'Cytokinins help overcome the apical dominance.'
Gibberellin (GA3) is the main hormone for internode and stem elongation. It causes bolting (sudden long stem before flowering in rosette plants like cabbage) and increases the length of grape stalks. Auxin promotes cell elongation at the tip level and phototropism, but the classic 'increase in stem/internode length' match answer is gibberellin.
Ethylene ripens fruit. It is a gas made by ripening fruits and ageing tissues, and one rotten fruit releasing ethylene ripens the whole basket. ABA (abscisic acid) is the stress and dormancy hormone; it does NOT ripen fruit. Trap: both start with vowels and both relate to abscission, but only ethylene ripens fruit and causes leaf/flower fall.
Abscisic acid (ABA). It stimulates closure of stomata during water stress and increases the plant's tolerance to stress, which is why ABA is called the 'stress hormone'. This is a favourite match-type pairing: ABA to 'stimulation of stomatal closure'.
Both. 2,4-D is a synthetic AUXIN, and it is used as a herbicide (weed killer) that kills dicot weeds without harming mature monocots. So in matching, 2,4-D pairs with 'herbicide' and belongs to the auxin group. Auxins also induce parthenocarpy (seedless fruits like tomato).
Cytokinin promotes cell division (cytokinesis) and delays leaf senescence (keeps leaves green longer, the Richmond-Lang effect), overcomes apical dominance, and promotes nutrient mobilisation. Common match pairings: cytokinin to 'cell division', 'delay of senescence', 'overcoming apical dominance', or 'nutrient mobilisation'.
Match List-I with List-II. List-I: (A) Auxin (B) Gibberellin (C) Cytokinin (D) Ethylene. List-II: (I) Promotes female flower formation in cucumber (II) Overcoming apical dominance (III) Increase in the length of grape stalks (IV) Promotes flowering in pineapple. Choose the correct answer:
Match List-I (Growth Regulator) with List-II (Function/Effect). List-I: A. 2,4-D B. GA3 C. Kinetin D. ABA. List-II: I. Brewing industry II. Stimulation of stomatal closure III. Herbicide IV. Nutrient mobilisation. Choose the correct answer:
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Fix ONE signature effect per hormone: Auxin = apical dominance and 2,4-D herbicide; Gibberellin = elongation, bolting, brewing/malting; Cytokinin = cell division and delaying leaf senescence; Ethylene = fruit ripening and female cucumber flowers; ABA = stomatal closure and seed dormancy. Match questions reuse these signatures.
Abscisic acid (ABA) is the main inhibitor (stress hormone, seed dormancy, stomatal closure). Ethylene also acts as an inhibitor in many cases (promotes senescence and abscission). The three promoters are auxins, gibberellins and cytokinins.
Ethylene (C2H4) is the only gaseous plant growth regulator. It is produced by ripening fruits and senescing tissues and moves through air, which is why one ripe fruit ripens others nearby.
Gibberellic acid (GA3). It speeds up the malting process, so 'brewing industry' pairs with GA3 in match-type questions, as tested in NEET 2026.
The auxin-to-cytokinin RATIO decides it. High auxin favours root formation, high cytokinin favours shoot formation, and a balanced combination gives both shoots and roots from callus.
