Flower - Plant Growth Substances

Floral initiation is a dramatic event involving a total changeover of the character and developmental pattern of the meristem. The stimulus can be internal i.e. age of the plant, endogenous hormones etc. and external factors like light (photoperiod) and temperature (vernalisation) as well.

External stimuli are perceived by a pigment called phytochrome which in turn triggers a series of steps including gene activation, new enzyme synthesis and rise of endogenous hormone levels. It is also possible that certain quiescent cells in the meristem may be carried along at the apex and become activated during floral initiation. However, it is also possible that genes which control floral initiation are different from those responsible for leaf development.