Formation of bound gibberellins inPharbitis nil

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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.3H-GA1 applied to youngPharbitis plants was converted to two water-soluble compounds present in the aqueous phase. The rate of conversion was significantly enhanced when3H-GA1 and14C-glucose were applied to the same plants. Chromatography indicated that one of the conversion products of3H-GA1 became at least partly associated with the applied14C-glucose (or its products). This suggestion was also supported by the fact that mild acid hydrolysis of the aqueous fraction resulted in the reappearance of3H-GA1 and a conversion product of3H-GA1, including a14C-radioactivity peak cochromatographing with14C-glucose. However, the conversion products obtained with3H-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.