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 wild-type plants, were determined by gas chromatography-selected ion monitoring (GC-SIM) using H-2 or C-13 internal standards. The mutants possessed similar GA1 levels to wild-type plants, consistent with their classification as GA-sensitivity rather than GA-synthesis mutants. However, these mutants differ from certain sensitivity mutants in other species, in which substantial accumulation of GA1 occurs. The results suggest that if the proposed feedback model for the regulation of GA synthesis 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 consistent with the hypothesis that in those GA-sensitivity mutants which do not accumulate C19 GAs, the biochemical lesion may be well down the transduction pathway which leads from GA1 reception to stem elongation.