GIBBERELLIN-GROWTH RETARDANT INTERACTIONS ON THE GROWTH AND FLOWERING OF CLERODENDRUM-THOMSONIAE

Gibberellin‐growth retardant interactions on the vegetative growth and flowering of the vine Clerodendrum thomsoniae Balf. were studied using both exogenous treatments and biologically testing the acid fraction attained from the plant extract. The growth retardant, ancymidol, greatly retarded stem elongation and markedly increased flowering under inductive environments. Gibberellin A3 (GA3) application to the shoot tip stimulated vine growth, prevented flowering under inductive environments, and completely overcame ancymidol‐induced effects. In contrast to GA3, treatment with GA7 had little effect on vegetative growth but increased flowering under inductive environments. The elevated activity of gibberellin‐like compounds, as determined by bioassay, were similar except for a marked increase in levels in ancymidol‐treated plants grown under inductive environmental conditions. Microscopic examination of the stem tip indicated that the action of the growth regulators involved the induction of floral buds. Thus, in Clerodendrum, ancymidol appears to stimulate an unknown gibberellin(s) and simultaneously acts antagonistically with GA3. Copyright © 1979, Wiley Blackwell. All rights reserved