Gibberellins (GAs) were identified and quantified during flower and fruit development in the Christmas rose (Helleborus niger L.), a native of south-eastern Europe with a long international horticultural tradition. Physiologically, the plant differs from popular model species in two major aspects: (i) following anthesis the, initially white or rose, perianth (formed, in this species, by the sepals) turns green and persists until fruit ripening ; and (ii) the seed is shed with an immature embryo, a miniature endosperm, and a prominent perisperm as the main storage tissue. GA1 and GA4 were identified by full-scan mass spectra as the major bioactive GAs in sepals and fruit. LC-MS/MS-selected ion monitoring in accord with previously verified protocols also afforded analytical data on 12 precursors and metabolites of GAs. In the fruit, GA4 peaked during rapid pericarp growth and embryo development and GA1 during the subsequent period of rapid nutrient accumulation in the seeds and continued pericarp enlargement. In the sepals, the flux through the gibberellin biosynthetic pathway was highest prior to the light green stage when the photosynthetic system was induced. Unfertilized, depistillated, and deseeded flowers became less green than the seed-bearing controls ; chlorophyll accumulation could be restored by applying GA1, GA4 and, less efficiently, GA3, to the deseeded fruit. The sepals of unfertilized and depistillated flowers indeed contained very low levels of GA4 and gradually decreasing levels of GA1. However, the concentrations of their precursors and metabolites were less affected. These data suggest that a signal(s) from the fruit stimulates GA biosynthesis in the sepals resulting in greening. The fruit derived GAs appear to be mainly involved in pericarp growth and seed development.

Biologija,Poljoprivreda