Florigen is the term used for the hypothesized hormone-like molecules that control and/or trigger flowering in plants. Its precise identity and mechanism are not known; only its function.

History

Florigen was first described by Russian plant physiologist Mikhail Chailakhyan in 1937, who demonstrated that floral induction can be transmitted through a graft from an induced plant to one that has not been induced to flower.

Anton Lang showed that several long-day plants and biennials could be made to flower by treatment with gibberellin, when grown under a noninducing photoperiod. This led Chailakhyan to modify his florigen hypothesis to postulate two classes of flowering hormones:

• Gibberellins
• Anthesin

Chailakhyan postulated that during noninducing photoperiods, long-day plants produce anthesin, but no gibberellin while short-day plants produce gibberellin, but no anthesin. However, these findings did not account for the fact that short-day plants grown under noninducing conditions (thus producing gibberellin) will not cause flowering of grafted long-day plants that are also under noninductive conditions (thus producing anthesin).

A possible hypothesis is that florigen does not exist; rather, a particular ratio of other hormones must be achieved for the plant to flower. However, recent experiments suggest that florigen does exist.

Recent Experiments

Recent work has implicated two genes, FT and CO, as possible components of the florigen signal.

See also

• Long day plant
• Short day plant
• Day neutral plant
• Photoperiodism
• Phytochrome

External links

• Press release on florigen
• History of the search for florigen

Plant physiology

Florigen