Q.The plant growth regulators are divided into growth promoters and growth inhibitors.
You're viewing a preview — the full solution, concept, methods & PYQ mapping are locked.
Start your 14-day free trial to unlock the full solution →The three growth-promoting hormones are auxins, gibberellins, and cytokinins; the inhibitory "stress hormone" is abscisic acid (ABA), which closes stomata and induces dormancy.
(a) Growth promoters: Plant growth regulators (PGRs) are broadly classified as growth promoters, which stimulate cell division, cell elongation, differentiation, flowering, fruiting, etc., and growth inhibitors, which suppress growth processes. The three major groups of growth-promoting hormones are:
- Auxins -- promote cell elongation, apical dominance, and root initiation.
- Gibberellins (GAs) -- promote stem elongation (internode elongation), seed germination, and flowering.
- Cytokinins -- promote cell division (cytokinesis) and delay senescence.
(b) The stress hormone: Abscisic acid (ABA) is the growth inhibitor known as the "stress hormone" of plants, because its levels rise sharply under adverse/unfavourable environmental conditions (such as drought or wilting), helping the plant cope with stress.
(c) Two roles of ABA:
- Stomatal closure: ABA accumulates during water stress and causes the guard cells to lose turgor, closing the stomata -- this reduces the rate of transpiration and helps the plant conserve water during drought. …
Unlock everything free for 14 days
- Full step-by-step solutions
- Concept-first explanations
- Methods, shortcuts & mistakes
- PYQ mapping + timed mock tests
Full access for 14 days. No credit card required.