GC-MS quantification of gibberellin A20-13-O-glucoside and gibberellin A8-2-O-glucoside in developing barley caryopses

Gibberellin A(20)-13-O-glucoside (GA(20)-13-O-Glc) and GA(8)-2-O-Glc were identified by GC-MS as permethylated derivatives in mature grains of both barley varieties Hordeum vulgare L. cv. Himalaya and cv, Salome. Changes of the pool size of these GA conjugates together with those of the parent GA(20) and GA(8) were estimated during seed ripening by internal standard quantification, The pools of GA(20) and GA(8) were found to reach a maximum and then to decrease to small amounts at the stage of full ripeness. The amounts of GA(20)-13-O-Glc were higher at the beginning of ripeness and then declined until full ripeness but these changes were not as pronounced as for free GA(20). Thus, in mature caryopses of both varieties cv. Himalaya and cv. Salome the content of GA(20)-13-O-Glc was three to four times higher than that of GA(20). The pool of GA(8)-2-O-Glc increased dramatically during the final stages of ripening, in cv, Himalaya earlier than in cv, Salome, and reflected the intensive GA(20) metabolism during ripening. This is the first report on the simultaneous quantification of the pools of GA-O-glucosides and their parent GAs during seed development on the basis of a GC-MS/internal standard technique. (C) 1998 Elsevier Science Ltd. All rights reserved.