METABOLISM OF GIBBERELLIN A-29 IN SEEDS OF PISUM-SATIVUM CV PROGRESS-NO-9 - USE OF [H-2] AND [H-3] AND [H-3]GAS, AND IDENTIFICATION OF A NEW GA CATABOLITE

The metabolism of GA29 in maturing seeds of Pisum sativum cv. Progress No. 9 was further investigated, and the utility of 2H-labelled GAs in conjuction with GC-MS is illustrated. Using [2α-2H1]GA29 as an internal standard, endogenous GA29 was shown to reach a maximal level (ca. 10 μg/seed) 27 days from anthesis, and to decline to ca. 1.6 μg/seed in mature seeds. In a time-course feed the metabolism of [2α-2H1] [2α-3H1]GA29 applied to 27 day old seeds, and of endogenous GA29, was compared from the 1H:2H ratios in the recovered GA29. Although both [2α-2H1] [2α-3H1]GA29 and endogenous GA29 were metabolised to the same limited extent to a putative conjugate, in the main metabolic process endogenous GA29 was preferentially converted to an untraceable (i.e. unlabelled) metabolite. In contrast, endogenous GA29 and [1β,3α-2H2] [1β,3α-3H2]GA29, derived from [1β,3α-2H2] [1β,3α-3H2]GA20 in a time-course feed, were metabolised in an identical manner. In the latter case isotope loss precluded identification of the metabolite. The structure (8) has been assigned to a GA catabolite present in maturing seeds and seedlings of pea. The isotope data are consistent with this compound being the hitherto untraced metabolite of GA29 in pea. © 1978 Springer-Verlag.