THE ENDOGENOUS GIBBERELLINS OF DWARF MUTANTS OF LETTUCE

The gibberellin (GA) content of E-1, a tall genotype of early flowering lettuce (Lactuca sativa L.), and of three selected GA-responsive dwarfs, dwf1, dwf2, and dwf2i, has been determined using C-13-labeled internal standards and gas chromatographymass spectrometry (GC-MS). In the shoots of the E-1 parent, GA1, 3-epi-GA1, GA3, GA5, GA8, GA19, GA20, GA29, and GA53 were identified by full scan GC-MS and Kovats retention indices. Purification by immunoaffinity chromatography selective for 13-hydroxy GAs, was necessary for GA identification. Relative to the parent E-1, the concentrations of GA1, GA8, GA20, and GA29 in the shoots of dwf2 plants were reduced to about 10% and in shoots of dwf2i plants to less than 50%. In dwf1 the levels of GA1, GA8, and GA29 were also reduced to less than 50% of the parent E-1, but the level of GA20 was fivefold higher than in E-1. Plant height was correlated with the endogenous levels of GA1 and GA8.