SEED AND 4-CHLOROINDOLE-3-ACETIC ACID REGULATION OF GIBBERELLIN METABOLISM IN PEA PERICARP

In this study, we investigated seed and auxin regulation of gibberellin (GA) biosynthesis in pea (Pisum sativum L.) pericarp tissue in situ, specifically the conversion of [C-14]GA(19) to [C-14]GA(20). [C-14]GA(19) metabolism was monitored in pericarp with seeds, deseeded pericarp, and deseeded pericarp treated with 4-chloroindole-3-acetic acid (4-Cl-IAA). Pericarp with seeds and deseeded pericarp treated with 4-Cl-IAA continued to convert [C-14]GA(19) to [C-14]GA(20) throughout the incubation period (2-24 h). However, seed removal resulted in minimal or no accumulation of [C-14]GA(20) in pericarp tissue. [C-14]GA(29) was also identified as a product of [C-14]GA(19) metabolism in pea pericarp. The ratio of [C-14]GA(29) to [C-14]GA(20) was significantly higher in deseeded pericarp (with or without exogenous 4-Cl-IAA) than in pericarp with seeds. Therefore, conversion of [C-14]GA(20) to [C-14]GA(29) may also be seed regulated in pea fruit. These data support the hypothesis that the conversion of GA(19) to GA(20) in pea pericarp is seed regulated and that the auxin 4-Cl-IAA can substitute for the seeds in the stimulation of pericarp growth and the conversion of GA(19) to GA(20).