Gibberellin biosynthesis mutations and root development in pea

Dwarf mutants of pea (Pisum sativum), with impaired gibberellin (GA) biosyn thesis in the shoot, were studied to determine whether the roots of these g enotypes 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 an d 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 elonga ted in response to applied GA, and recombining na with mutation sin (which blocks GA catabolism) increased GA, levels in root tips and completely rest ored normal root development. In shoots, Mendel's le-1 mutation impairs the 3 beta -hydroxylation of GA(20) to the bioactive GA(1), resulting in dwarf ism. However, GA(1) and GA(20) levels were normal in le-1 roots, as was roo t 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 norm al root elongation in pea, and indicate that a 3 beta -hydroxylase gene oth er than LE operates in pea roots.