The genetic control of flowering in pea

The transition from vegetative to reproductive growth is a key event during plant development, in many species, the timing of this change depends on the length and spectral quality of the photoperiod. Extensive research supports the notion that the site of light perception in the leaf and the site af flower initiation in the apex are linked by the action of mobile, hormone-like substances. Physiological characterization of flowering mutants in the garden pea has identified two distinct mobile regulators of flowering produced in the leafy shoot - a floral stimulus and an inhibitor, The stimulus is specific to the flowering process and is thought to be constitutively produced. In contrast, the inhibitor affects both reproductive and vegetative growth and is strongly regulated. Photoperiod sensitivity is mainly conferred by a phytochrome A-mediated reduction in inhibitor level.