Dwarf mutants of pea (Pisum sativum), with impaired gibberellin (GA) biosynthesis in the shoot, were studied to determine whether the roots of these genotypes had altered elongation and GA levels. Mutations na, lh-2, and ls-1 reduced GA levels in root tips and taproot elongation, although in lh-2 and ls-1 roots the reduction in elongation was small (less than 15%). The na mutation reduced taproot length by about 50%. The roots of na plants elongated in response to applied GA 1 and recombining na with mutation sln (which blocks GA catabolism) increased GA 1 levels in root tips and completely restored normal root development. In shoots, Mendel's le-1 mutation impairs the 3␤-hydroxylation of GA 20 to the bioactive GA 1 , resulting in dwarfism. However, GA 1 and GA 20 levels were normal in le-1 roots, as was root development. The null mutation le-2 also did not reduce root GA levels or elongation. The results support the theory that GAs are important for normal root elongation in pea, and indicate that a 3␤-hydroxylase gene other than LE operates in pea roots.

The spontaneous, single‐gene dominant, pea (Pisum sativum L.) mutant bushy is characterised by short, thin stems, tiny leaves and a proliferation of basal lateral branches. We symbolised the dominant mutant allele bsh and the recessive wild‐type allele BSH. Some effects were very large, e.g. the reduction in internode length was around 10‐fold in pure mutant plants. The effect on branching was qualitative under our conditions as the wild‐type did not branch and the mutant branched extensively. Analysis of epidermal cells indicated the reduction in internode length arose principally from a reduction in cell length. The bushy mutation also altered root morphology with a reduction in the number and length of lateral roots. Time to first open flower was increased but node of flower initiation was not affected. In a few cases, bushy plants died before producing an open flower even though tiny abortive flower buds were produced in the upper leaf axils. In pure mutant plants, individual seed weight was reduced by 30%, number of seeds per pod was reduced 3‐fold, and seed number per plant was reduced 4‐fold. However, pod size was essentially normal for a given seed content, and the flowers were fertile and of normal structure. Grafting studies showed the primary action of the bushy mutation occurred in the shoot. In summary, the reduced cell and shoot elongation, loss of apical dominance and a primary action in the shoot, all point toward auxin deficiency (or perceived deficiency) as a possible cause of the bushy phenotype. The overall characteristics of bushy make it a useful mutant for research on plant development.

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We describe a new mutation, lrs, which reduces internode length in Pisum sativum L. The mutation appears to act by reducing both GA synthesis and the response to GA1. The levels of the 13‐hydroxylated GAs, GA53, GA44, GA19, GA20, GA1, and GA8 in the lrs mutant were greatly reduced compared with the wild‐type. The extent of the reduction in GA1 content in the apical tissues would, at least in part, account for the dwarf phenotype of the mutant. The reduced GA responsiveness of the new mutant was indicated by the inability of applied GA1 to remove the difference in elongation between lrs and LRS plants. The lrs mutant appears to be unique amongst internode length genotypes, possessing characteristics of both GA synthesis and GA response mutants.