Further Identification of Endogenous Gibberellins in the Shoots of Pea, Line G2

To interpret the metabolism of radiolabeled gibberellins A(12)-aldehyde and A(12) in shoots of pea (Pisum sativum L.), the identity of the radiolabeled peaks has to be determined and the endogenous presence of the gibberellins demonstrated. High specific activity [(14)C]GA(12) and [(14)C]GA(12)-aldehyde were synthesized using a pumpkin endosperm enzyme preparation, and purified by high performance liquid chromatography (HPLC). [(14)C]GA(12) was supplied to upper shoots of pea, line G2, to produce radiolabeled metabolites on the 13-OH pathway. Endogenous compounds copurifying with the [(14)C]GAs on HPLC were analyzed by gas chromatography-mass spectrometry. The endogenous presence of GA(53), GA(44), GA(19) and GA(20) was demonstrated and their HPLC peak identity ascertained. The (14)C was progressively diluted in GAs further down the pathway, proportional to the levels found in the tissue and inversely proportional to the speed of metabolism, ranging from 63% in GA(53) to 4% in GA(20). Calculated levels of GA(20), GA(19), GA(44), and GA(53) were 42, 8, 10, and 0.5 nanograms/gram, respectively.