PHOTOINDUCTION OF FLOWER IDENTITY IN VEGETATIVELY BIASED PRIMORDIA

Far-red light and long photoperiods promote flowering in Arabidopsis. We report here that when 30-day-old vegetative plants were induced wit h a continuous light treatment enriched in far-red light, flowers deve loped directly from previously initiated primordia. Specifically, plan ts induced with our continuous incandescent-enriched (CI) treatment pr oduced an average of two primary-axis nodes with a leaf/flower phenoty pe, indicating that approximately two leaf/paraclade primordia per pla nt produced an individual flower from tissue that typically would diff erentiate into a paraclade (secondary inflorescence). Assays for APETA LA1::beta-glucuronidase activity during the CI photoinduction treatmen t indicated that the floral meristem identity gene APETALA1 was transc riptionally activated in primordia with a leaf/paraclade bias and in p rimordia committed to leaf/paraclade development. APETALA1 ::P-glucuro nidase activity levels were initially highest in young primordia but w ere not correlated strictly with primordium fate. These results indica te that primordium fate can be modified after primordium initiation an d that developing primordia respond quantitatively to floral induction signals.