INTERNODE LENGTH IN PISUM - MUTANTS LK, LKA, AND LKB DO NOT ACCUMULATE GIBBERELLINS

The levels of gibberellin A1 (GA1), GA8, GA19, GA20, GA29, and GA44 in the short Pisum sativum L. mutants lk, lka, and lkb, and comparable w ild-type plants, were determined by gas chromatography-selected ion mo nitoring (GC-SIM) using H-2 or C-13 internal standards. The mutants po ssessed similar GA1 levels to wild-type plants, consistent with their classification as GA-sensitivity rather than GA-synthesis mutants. How ever, these mutants differ from certain sensitivity mutants in other s pecies, in which substantial accumulation of GA1 occurs. The results s uggest that if the proposed feedback model for the regulation of GA sy nthesis occurs in peas it is not the reduced growth per se that is the trigger for elevated levels of C19 GAs. The results are also consiste nt with the hypothesis that in those GA-sensitivity mutants which do n ot accumulate C19 GAs, the biochemical lesion may be well down the tra nsduction pathway which leads from GA1 reception to stem elongation.