METABOLISM OF GIBBERELLIN A(12) AND A(12)-ALDEHYDE AND THE IDENTIFICATION OF ENDOGENOUS GIBBERELLINS IN POTATO (SOLANUM-TUBEROSUM SSP ANDIGENA) SHOOTS

Metabolism of [C-14]gibberellin(GA)(12)-aldehyde and [C-14]GA(12) in vegetative tissue of potato (Solanum tuberosum ssp. andigena) was studied by supplying solutions of these compounds to the base of isolated shoot tips and analyzing the metabolic products by radiodetection after HPLC. Endogenous gibberellins that co-eluted with the C-14-metabolites on HPLC were identified by GC-MS as GA(53)-aldehyde, GA(53), GA(44), GA(19), GA(20), GA(29), GA(1), and GA(8). Thus the early-13-hydroxylation pathway seems to be a major pathway in vegetative potato shoots. This was confirmed by time-course feeding studies; according to HPLC elution profiles, the members of the pathway were produced from [C-14]GA(12)-aldehyde and [C-14]GA(12) in the expected time sequence. The formation of GA(53) appeared to be predominantly via GA(12) rather than GA(53)-aldehyde. The detection of endogenous GA(51) suggests that the non-hydroxylation pathway was also active. Comparisons of HPLC retention times of radioactive metabolites before base hydrolysis with retention times after base hydrolysis showed that potato shoots can conjugate several GAs. HPLC retention times of other radioactive metabolites corresponded with previously published retention times of GA(29)-catabolite, GA(51)-catabolite, GA(12)-aldehyde-conjugate, and GA(53)-aldehyde-conjugate.