Class 11 NEET Biology Plant Growth and Development

(a) : In vascular plants especially the taller ones, if the apical bud is intact and growing of the lateral bud remains suppressed, removal of apical bud causes fast growth of lateral buds. This influence of apical bud in suppressing the growth of lateral buds is termed as apical dominance.
Indole-3-acetic acid (IAA) is a natural auxin which is responsible for apical dominance.
GA is Giberrellic acid causes rapid elongation growth. ABA (abscisic acid) is a powerful growth inhibitor. Florigen is a chemical involved in flowering.