Internode length in Pisum. Estimation of GA₁ levels in genotypes Le, le and led

The levels of GA 1 , 3‐epiGA 1 and GA 8 in genotypes Le, le and le d of Pisum sativum L. were determined by gas chromatography‐selected ion monitoring (GC‐SIM) after feeds of [ 3 H, 13 C]‐GA 20 to each genotype. The levels of endogenous and [ 13 C]‐labelled metabolites were determined by reverse isotope dilution with unlabelled GA 1 , 3‐epiGA 1 and GA 8 . The results demonstrate a quantitative relationship between the level of GA 1 and the extent of elongation both on a per plant and a per g fresh weight basis. These results are consistent with previous findings in peas and other species possessing a predominant early 13‐hydroxylation pathway for GA biosynthesis. The levels of 3‐epiGA 1 also decreased in the genotypic sequence Le, le, le d although not as rapidly as for the level of GA 1 . This may suggest that the alleles at the le locus also influence the formation of 3‐epiGA 1 .