florigen

Florigen is a hypothetical signaling molecule that triggers flowering in plants, produced in leaves and transported to the shoot apical meristem where it initiates the transition from vegetative to reproductive development. The concept was proposed in the 1930s by the Russian scientist D. K. Chailakhian, who suggested a mobile flowering signal originates in leaves and travels through the phloem to the shoot apex.

Over time, molecular genetics identified FLOWERING LOCUS T (FT) and related proteins as the best-supported molecular embodiment of florigen in many species. FT is produced in leaves under inductive photoperiods and then moves through the phloem to the shoot apex, where it interacts with the FD transcription factor to activate a flowering program, including genes such as AP1 and SOC1. In Arabidopsis, FT-like proteins (such as TSF) serve as central mobile signals, though the exact mechanism of movement and action can vary among species.

The florigen signal integrates environmental cues such as day length with endogenous signals to enable flowering at an appropriate time. This concept has had broad implications for agriculture, offering routes to manipulate flowering time in crops and ornamentals to optimize yield and adaptation.

Current research continues to refine understanding of florigen, including how the signal is loaded into and moves through the phloem, whether additional mobile signals accompany FT-like florigen, and how these processes differ across diverse plant groups.