Photoperiodic flowering of Arabidopsis : integrating genetic and physiological approaches to characterization of the floral stimulus

In many plants the transition from vegetative growth to flowering is controlled by environmental cues. One of these cues is day length or photoperiod, which synchronizes flowering of many species with the changing seasons. Recently, advances have been made in understanding the molecular mechanisms that confer photoperiodic control of flowering and, in particular, how inductive events occurring in the leaf, where photoperiod is perceived, are linked to floral evocation that takes place at the shoot apical meristem. We discuss recent data obtained using molecular genetic approaches on the function of regulatory proteins that control flowering time in Arabidopsis thaliana . These data are compared with the results of physiological analyses of the floral transition, which were performed in a range of species and directed towards identification of the transmitted floral singals. Key-words: Arabidopsis ; floral signals; flowering; flowering time gene; phloem; photoperiodic floral induction.