Flower development pathways

This diagram displays our current knowledge of the signaling pathways that promote flowering and of how floral architecture is determined in Arabidopsis. The model is based mainly on genetic interactions between mutants affected in flowering time, floral meristem identity and floral organ identity. Some interactions, such as the activation of the transcription of floral organ identity genes by LEAFY, have also been confirmed at the molecular level.Light is perceived by photoreceptors and, if the circadian clock identifies long photoperiods, activates a facultative long-day pathway (shown in red). If the photoperiod is short, flowering depends exclusively on a gibberellin-dependent pathway (shown in yellow) and on a photoperiod-independent pathway that is primarily responsive to temperature (shown in blue). The metabolic state of the plant is reflected in the amount of circulating sucrose (shown in pink), which also promotes flowering. The ultimate targets for the flowering-time pathways are the floral meristem identity genes (shown in green), whose activity confers floral identity to newly emerging primordia. The correct arrangement of floral organs is established initially by the floral organ identity genes, whose regionalized expression is a consequence of activation by floral meristem identity proteins and mutual interactions (shown in brown).