ANTAGONISTIC AND SYNERGISTIC INTERACTIONS BETWEEN ANCYMIDOL AND GIBBERELLINS IN SHOOT GROWTH OF CUCUMBER (CUCUMIS-SATIVUS L)

Effects of the plant growth retardant, ancymidol, on the growth and morphology of the shoot system of cucumber (Cucumis sativus L. ) were investigated. Ancymidol inhibited stem elongation, reducing both number and length of internodes. Reduction in leaf area, attributable to a reduction in both cell size and number, was accompanied by an increase in chlorophyll per unit area. The retardant decreased apical dominance and delayed anthesis. Gibberellic acid fully reversed ancymidol-induced inhibition of stem elongation, internode length and production, and leaf expansion. GA4/7 and ancymidol gave a synergistic promotion of stem elongation by increasing elongation of younger internodes and increasing internode production. Synergistic promotion of petiole elongation by this combination was also observed. Ancymidol, applied 7 d previously either to the shoot or root, severely reduced the level of gibberellin-like activity in bleeding sap collected from decapitated plants. © 1979 Oxford University Press.