Gibberellin‐Growth Retardant Interactions on the Growth and Flowering of Clerodendrum thomsoniae

Abstract

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.

Effectiveness of gibberellins and 6‐benzyladenine on flowering of Arabidopsis thaliana

“…This activation dominated the stimulation of axial cells linked with the transition to flowering. Interactions between vegetative growth and reproductive development are thus established, as for Clerodendrum (Koranski et al 1979). In connection with suboptimal photoperiodic or thennoperiodic treatments, applied GA3 and, to a lesser degree, cytokinins may enhance the flowering response of A. thaliana, as for Chrysanthemum morifolium (Bennink 1974).…”

Growth retardants on development and ornamental quality of potted 'Lilliput' Zinnia elegans Jacq.

“…Flowering delay after daminozide application could derive from a blockage of gibberellin biosynthesis or from a wholly or partly restriction in action of one or more active endogenous gibberellins, which may be flowering promoters. Growth retardants action can be relatively specific for each giberellin (Koranski et al, 1979). Thus, growth retardant could decrease the synthesis of gibberellin, that promote main stem and side branches elongation and, simultaneously, promote or inhibit the synthesis of gibberellin, that promote flowering.…”

Hormonal Aspects of Phase Change and Precocious Flowering

“…As noted above for Rhus and Callistemon, where GA 3 will cause juvenile flowering, in Clerodendron thomsoniae, GA? gives a slight promotion while GA 3 inhibits flowering in cutting-grown plants (KORANSKI et al 1979). In Vitis vinifera, GA 3 causes the precocious formation of anlagen, the morphogenetic precursor of the tendril and inflorescence, at nodes lower than expected in sexually mature plants (SRINI-VASAN andMULLINS 1979, 1980).…”