Figure 5.

Photoperiod dependency of the DE response in Arabidopsis. Drought stress, largely via ABA signaling, promotes the DE response under LDs but not SDs. Photoperiod-activated GI may relieve the transcriptional repression at the FT/TSF promoters, thus facilitating their ABA-dependent up-regulation. Increased florigen levels trigger SOC1 activation, which in turn contributes to TSF up-regulation. A floral delay occurs under SDs upon drought conditions. Drought and/or ABA may enhance the activity of different repressor complexes (e.g. SVP/FLC or other repressors [R]) through an unknown mechanism, thus interfering with the floral transition.