GIBBERELLIN BIOSYNTHESIS FROM GIBBERELLIN A12-ALDEHYDE IN A CELL-FREE SYSTEM FROM GERMINATING BARLEY (HORDEUM-VULGARE L, CV HIMALAYA) EMBRYOS

Gibberellin (GA) metabolism from GA12-aldehyde was studied in cell-free systems from 2-d-old germinating embryos of barley. [C-14]- or [17-H-2(2)]Gibberellins were used as substrates and all products were identified by combined gas chromatography-mass spectrometry. Stepwise analysis demonstrated the conversion of GA12-aldehyde via the 13-deoxy pathway to GA51 and via the 13-hydroxylation pathway to GA29, GA1 and GA8. In addition, GA3 was formed from GA20 via GA5. We conclude that the embryo is capable of producing gibberellins that can induce alpha-amylase production in the aleurone layer. There was no evidence for 12-beta- or 18-hydroxylation and GA4 was neither synthesised nor metabolised by the system. All metabolically obtained GAs, with the exception of GA3, were also found as endogenous components of the cell-free system in spite of ammonium-sulfate precipitation and desalting steps.