Metabolism of Tritiated Gibberellin A20 in Immature Seeds of Dwarf Pea, cv. Meteor

Tritium-labeled gibberellin A(20) ([(3)H]GA(20)) was applied via the pedicel to immature pods and seeds of dwarf peas and three harvests were made at days 5, 10, and 23 (mature) after application. Of the five metabolites of [(3)H]GA(20), the three in highest yield were GA(29), an alpha,beta-unsaturated ketone, and a compound (B), whose structure was only tentatively assigned. The metabolic sequence GA(20) --> GA(29) --> compound B --> the ketone was indicated. The amount of [(3)H]GA(29) in both seeds and pods was highest at day 5 and declined to its lowest level at maturity. The amount of the [(3)H]ketone in the seed increased with time to its highest level at maturity. It is suggested that compound B and the ketone represent the major pathway of catabolism of GA(29), a 2beta-hydroxylated GA of low biological activity, and that the ketone is not metabolized, or only slowly metabolized, during seed maturation.