INTERNODE LENGTH IN PISUM - THE LRS MUTATION REDUCES GIBBERELLIN RESPONSE AND LEVELS

We describe a new mutation, irs, which reduces internode length in Pis um sativum L. The mutation appears to act by reducing both GA synthesi s and the response to GA(1). The levels of the 13-hydroxylated GAs, GA (53), GA(44), GA(19), GA(20), GA(1), and GA(8) in the lrs mutant were greatly reduced compared with the wild-type. The extent of the reducti on in GA(1) content in the apical tissues would, at least in part, acc ount for the dwarf phenotype of the mutant. The reduced GA responsiven ess of the new mutant was indicated by the inability of applied GA(1) to remove the difference in elongation between lrs and LRS plants. The lrs mutant appears to be unique amongst internode length genotypes, p ossessing characteristics of both GA synthesis and GA response mutants .