Florigen

Florigen (or flowering hormone) is the hypothesized hormone-like molecules responsible for controlling and/or triggering flowering in plants. Florigen is produced in the leaves and acts in the shoot apical meristem of buds and growing tips. It is known to be graft-transmissible and even functions between species. However, despite having been sought since the 1930s, the exact nature of florigen is still a mystery.