Seedling growth and the metabolism of high specific activity (1.1ensp;TBqensp;mmolminus;1) 3Hgibberellin A1were studied in two Canadian maize (Zea maysL.) inbreds, CM7 and CM49, and in their single cross F1hybrid. As previously reported, the hybrid grew more rapidly than either parental inbred. Metabolism of the 3HGA1was qualitatively similar in all three genotypes and 3H-labelled metabolites were tentatively identified through sequential, step-elution silicic acid partition chromatography followed by reversed-phase C18high-performance liquid chromatography, relative to the retention times of authentic GAs. Although the expected 2beta;-hydroxylation product, 3HGA8was not detected, a metabolite was observed at the retention time of GA8-O(2)-glucoside. Additionally, another metabolite(s) eluted at the retention time of glucosyl conjugates of GA1, and enzymic cleavage with cellulase yielded a 3H-labelled compound which subsequently eluted at the retention time of free GA1. While the ratio of the precursor 3HGA1to total 3HGA conjugate-like metabolites was similar in the three genotypes, the hybrid contained higher levels of the 3HGA8-glucosidelike metabolite, whereas the inbreds contained higher levels of the 3HGA1conjugatelike metabolite(s). Thus, there are differential rates of GA1metabolism in a maize hybrid relative to its slower-growing inbred parents.
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