Florigen

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Florigen or Flowering hormone are the terms 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.

1 History
2 Recent Experiments
3 See also
4 External links

[edit] 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). The flowering hormone has eluded scientists for over sixty years, as the flowering response has been found to be increasingly complex.

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. Its existence is substantiated by experiments that indicate that the substance that triggers blooming is produced or activated in the leaves of the plant, and must be given time to pass out of the leaves before the plant can flower.

[edit] Recent Experiments

Recent work has implicated two genes, FT and CO, as possible components of the florigen signal. A review of recent (2006) progress in the quest for florigen can be found at [1].