The Mystery of the Flowering Hormone Solved?

Flower dinoThe Mystery

About 150 million years ago dinosaurs were disappearing from the Earth, and flowering plants were appearing.

Since that time, flowering plants (angiosperms) have flourished, rapidly diversifying and spreading into virtually every landscape on the planet. Charles Darwin referred to this abrupt origin and highly accelerated rate of diversification of angiosperms an “abominable mystery”. (Please see ref. 1 below for an excellent review.)

Another great botanical mystery over the past 100 years has to do with what induces plants to make flowers.

Young (juvenile) angiosperms don’t have flowers. They make just roots, shoots and leaves. But at some point during their lifetime, they begin to make flowers. The mystery was: what triggered flowering?

A major clue in solving this mystery happened about 100 years ago when scientists discovered evidence for a flower-inducing signal, produced in the leaves, that later was named florigen.

Discovering the nature of florigen has taken nearly 100 years. But recently scientists likely have not only identified florigen but also have pieced together how it works to induce flowering.

Mystery Solved?432px Arabidopsis thaliana

The latest scientific evidence supports the hypothesis that florigen is actually a protein called FT coded for by the gene Flowering Locus T in Arabidopsis. (Please see refs. 2 & 3 below for current reviews of the subject.)

Briefly, FT is produced in the leaves and is transported via the phloem to the shoot apical meristems (SAM). Here FT acts like a molecular “alarm-clock”, evoking a complex genetic scenario, which culminates in flower formation. (Please see my YouTube video for an overview of the genetics of flowering.)

Making Plants Flower At Will?

Can scientists now induce plants to flower at will by simply spraying a “flowering hormone” on them?

The answer is: Not yet, but maybe someday real soon.

Recent experiments indicate that the first commercially-available plants you’ll likely see will be genetically-engineered to over-express the FT gene under special conditions. (See ref. 4, for example.)

The Flowering Locus T gene codes for the FT protein, which most biologists currently agree is indeed florigen.

Presuming the plant is competent to flower, then the sudden appearance of lots of florigen would probably “tip the scales” to induce flowering in responsive SAMs.

To “turn on” the Flowering Locus T genes, one could engineer them to be activated by alcohol (ethanol), for example. So that to induce such an engineered plant to flower, one would merely need to spray a dilute solution of alcohol (wine?) on the leaves.

8/16/2011 – This just in: Florigen receptor in rice identified.

Shameless Plug

I’ve just finished a newly-updated ebook on flowering. If you’re interested, click on the eBooks tab above. Or, if you prefer, check it out on the iTunes bookstore, at Amazon’s Kindle store, and even at the Barnes & Noble Nook bookstore. Thanks.


1. Friedman, William E. (2009) The meaning of Darwin’s “abominable mystery”. American Journal of Botany, vol. 96, pp. 5-21. (Full Text)

2. Amasino, R. (2010) Seasonal and developmental timing of flowering. The Plant Journal, Vol. 61, pp. 1001-1013. (Full Text)

3. Wigge, P. A. (2011) FT, a mobile developmental signal in plants. Current Biology, Vol. 21, R374-R378. (Full Text)

4. Yeoh, C.C., M. Balcerowicz, R. Laurie, R. Macknight and J. Putterill (2011) Developing a method for customized induction of flowering. BMC Biotechnology vol. 11, p. 36. (Full Text) © 2008-2011 All Rights Reserved.

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