Which one of the plant growth regulators would you use if you are asked to: (a) induce rooting in a twig (b) quickly ripen a fruit (c) delay leaf senescence (d) induce growth in axillary buds (e) ‘bolt’ a rosette plant (f) induce immediate stomatal closure in leaves.

(a) induce rooting in a twig

Use an auxin such as indole-3-butyric acid (IBA) or naphthalene acetic acid (NAA); these hormones stimulate cell division and differentiation in cuttings, promoting adventitious root formation

(b) quickly ripen a fruit

Apply ethylene gas—it’s the natural ripening agent that triggers softening, color change, and flavor development in fruits

(c) delay leaf senescence

Use cytokinins; they slow senescence by maintaining chlorophyll, promoting nutrient mobilization, and delaying leaf yellowing

(d) induce growth in axillary buds

Apply cytokinins; they break apical dominance and stimulate axillary bud outgrowth, promoting branching

(e) ‘bolt’ a rosette plant

Use gibberellins; they promote stem elongation and induce bolting in rosette-form plants

(f) induce immediate stomatal closure in leaves

Apply abscisic acid (ABA); it triggers rapid stomatal closing by inducing ion efflux from guard cells, reducing water loss under stress