Interaction of Gibberellin A3and Ancymidol in the Growth and Cell-Wall Extensibility of Dwarf Pea Roots

摘要

Effects of ancymidol (Anc) and gibberellin A3(GA3) on root growth, osmotic concentration and cell-wall extensibility of the root were investigated in the gibberellin-sensitive cultivar of dwarf pea, Little Marvel. Anc strongly suppressed elongation of both shoots and roots in darkness. Although the elongation of shoots of this dwarf cultivar was severely retarded in the light, it was repressed still further by Anc. GA3promoted elongation of shoots both in the presence and in the absence of Anc, whereas it reversed suppression of root elongation by Anc. The concentration of GA3required for the recovery of root elongation was lower than that required for the promotion of shoot elongation. Treatment with Anc led to increased thickening of roots with increased numbers of cells per cross section and lateral expansion of cells in the cortex.GA3had little effect on the osmotic concentration of cell sap obtained from root segments. Anc-treated roots did not respond to acid solutions by elongation, whereas GA3-treated roots responded normally to such solutions. Anc suppressed but GA3enhanced the cell-wall extensibility of roots as measured in vivo and in vitro.These results indicate that a low concentration of gibberellin plays a role in normal elongation of roots by maintaining the extensibility of the cell wall in this gibberellin-sensitive dwarf pea.