Formation of bound gibberellins inPharbitis nil

Abstract

Developing seeds ofPharbitis nil accumulate free as well as bound gibberellins until a maximum level is reached at approximately 25 days after anthesis. Seeds from CCC-treated parent plants have a strongly reduced level of free as well as bound gibberellins. When different spray reagents were used it was found that trichloroacetic acid in particular was suitable to locate non-hydrolysed bound GA fractions on thin-layer plates. Chromatography showed two major bound GA fractions, determined with spray reagents as well as by means of hydrolysis.(3)H-GA1 applied to youngPharbitis plants was converted to two water-soluble compounds present in the aqueous phase. The rate of conversion was significantly enhanced when(3)H-GA1 and(14)C-glucose were applied to the same plants. Chromatography indicated that one of the conversion products of(3)H-GA1 became at least partly associated with the applied(14)C-glucose (or its products). This suggestion was also supported by the fact that mild acid hydrolysis of the aqueous fraction resulted in the reappearance of(3)H-GA1 and a conversion product of(3)H-GA1, including a(14)C-radioactivity peak cochromatographing with(14)C-glucose. However, the conversion products obtained with(3)H-GA1 applied to plants appeared to be chromatographycally different from any of the bound-GA fraction established by means of hydrolysis or spray reagents in developing seeds.