Question

In unisexual plant, sex can be changed by the application of
A. Ethanol
B. Auxins
C. Cytokinin
D. ABA

Answer 1

Hint: Gregg's explain about the effects of auxin on ethylene production in the plants. Auxin has several effects on plant growth and development of plant and sex organ and change in sex of the plant.

Complete answer:
In this question, we have been asked about the hormone which can change the sex of a unisexual plant. Sex change is a process by which a plant changes sex, by which female sexual characteristics are substituted for male ones or vice versa. As we know each unisexual plant produces either functionally male flowers or functionally female flowers.
So, we have four options. Our first option is ethanol. When ethanol is applied to a plant, it tends to slow the growth of plants. The second option is Auxins. As we know, auxin is a plant hormone, which promotes stem elongation, inhibits growth of lateral buds, flowers and maintains apical dominance. Auxin also stimulates the production of ethylene. Auxin promotes female flowers and ethylene also exert feminizing effects. So, too much use of auxin can lead to sex change in plants. Option C is cytokinin. As we know, cytokinin induces cell proliferation and triggers callus differentiation to shoot when applied with auxins, but now it is known that cytokinins help in plant growth and development, embryogenesis, and maintenance of root and shoot meristems. Our last option is ABA. As we know ABA is abscisic acid. ABA promoted the female tendency of gynoecious plants, but did not change the sex of monoecious plants.

So, the correct option is B. Auxins.

Note:
Recently, three growth hormones—auxin, ethylene and gibberellin have been found that participate in sex expression. Among them, auxin is known to promote femaleness in monoecious plants.