Q127
General ScienceBiology
Which hormone is responsible for breaking the dormancy of a seed?
- a.Auxin
- b.Dormin
- c.Cytokinin
- d.Gibberellin
Answer: (D) Gibberellin
Gibberellins (for example gibberellic acid, $GA_3$) break the dormancy of seeds and buds, promote stem elongation and bolting, and trigger the enzyme α-amylase in germinating cereal grains. They were discovered through the "foolish seedling" (bakanae) disease of rice caused by the fungus Gibberella fujikuroi. Dormin is the old name of abscisic acid (ABA), the stress hormone that does the opposite: it induces dormancy and closes stomata. Auxin controls cell elongation, apical dominance and phototropism; cytokinin promotes cell division and delays ageing of leaves. Ethylene, a gas, ripens fruit.