Plant Growth And Development

Question

The phenomenon in which the growing apical bud suppresses the growth of the lateral buds below it is governed mainly by which hormone produced at the shoot tip?

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Apical dominance is a classic auxin-mediated phenomenon covered in NCERT Class 11, Chapter 15 (Plant Growth and Development). Auxin synthesised at the growing apical bud moves downward and inhibits the growth of the lateral or axillary buds situated below, keeping the plant growing primarily along its main axis. This is why removal of the shoot tip, as in pruning or decapitation, releases the lateral buds from suppression and promotes bushy, branched growth. Gibberellin is associated with internode elongation rather than the suppression of lateral buds, so it is not the controlling hormone here. Cytokinin actually counteracts apical dominance by promoting the growth of lateral buds, acting opposite to auxin. Abscisic acid governs dormancy and stress responses, not the maintenance of apical dominance. A biological consistency check supports the answer: since cutting off the auxin-producing apex relieves the inhibition and lateral branches sprout, the inhibitory signal from the tip must be auxin, confirming its central role in apical dominance, and the restoration of dominance by applying auxin to the cut surface, which prevents the lateral buds from sprouting, firmly seals the conclusion.

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