Figure 3.

Photoperiodic control of flowering and growth. The pathways controlling (A, B) flowering time in Arabidopsis and (C, D) growth cessation in Populus spp. involve similar components. Short days promote (A) vegetative growth in Arabidopsis and (C) bud set in Populus spp.; long days promote (B) flowering in Arabidopsis and (D) bud break and growth in Populus spp. Photoperiodic responses in each species are controlled by external coincidence. In long days in Arabidopsis, FKF1 and GI stabilize CO, leading to FT expression which promotes flowering. In Populus spp, LHY2 controls FT2 expression directly as well as via control of coincidence of FKF1 and GI. FT2 promotes growth. In SDs in Arabidopsis, CO degrades before it is able to promote FT. Further details are provided in the text. Arrows show positive effects; bars show negative effects. Black, dotted lines indicate inactivate pathways; blue and red dotted lines indicate light transduction via photoreceptors promoting protein stability; rainbow or yellow arrow indicates perceived light. Inactivated products appear in grey.