Question

Which of the following is a hypothetical hormone?

• A. Gibberellin
• B. Auxin
• C. Cytokinin
• D. Florigen

Answer 1

The correct option is D Florigen

Experiments in which different tobacco species are grafted together indicate that unidentified flower-promoting and flower inhibiting substances may exist. Nicotiana sylvestris is a long-day tobacco plant (it requires a short night to flower); a variety of N. tabacum is a day-neutral tobacco plant (seasonal changes do not affect when it flowers). When a long-day tobacco is grafted to a day-neutral tobacco and exposed to short nights, both plants flower. The day-neutral tobacco plant flowers sooner than it normally would. Biologists hypothesize that a flower-promoting substance, florigen, may be induced in the long-day plant and transported to the day-neutral plant through the graft union, causing the day neutral tobacco plant to flower sooner than expected. An intact plant may produce florigen in the leaves and transport it in the phloem to the shoot apical meristem. There, it induces a transition from vegetative to reproductive development that is, to a meristem that produces flowers.

Thus, the correct answer is option D.