Gibberellins and the floral transition in <i>Sinapis alba</i>

Abstract

The putative role of gibberellins in the transition to flowering was investigated in Sinapis alba , a caulescent long‐day (LD) plant. It was observed that: (1) physiological doses of exogenous gibberellins (GA 1 , GA 3 , GA 9 ) do not cause the floral shift of the meristem when applied to plants grown in short days but have some positive effect on the flowering response to a suboptimal LD; no inhibition was observed in any case; (2) GA‐biosynthesis inhibitors (prohexadione‐Ca and paclobutrazol) considerably inhibit stem growth but have some negative effect on flowering only when a suboptimal LD is given; and (3) the floral transition induced by one 22‐h LD does not correlate with any detectable change in GA content of the apical bud, of the leaves, and of the phloem exudate reaching the apex. Taken together, these results suggest that GAs do not act as a major signal for photoperiodic flower induction in Sinapis .