EFFECT OF PLANT-GROWTH REGULATORS ON FLOWER DEVELOPMENT IN THE GRAPEVINE (VITIS-VINIFERA L) CV CABERNET-SAUVIGNON

Grapevine cuttings induced to retain flowers by the Mullins technique were treated with plant growth regulators (PGRs) in various combinations or at different concentrations. Gibberellin A3 (GA3) at 100 ppm increased flower number, inflorescence branching, curvature and length of the rachis, but decreased leaf number. Adding kinetin (300 ppm) to GA3 eliminated the effect on flower number and leaf number. Indole acetic acid (IAA) reduced flower number and curvature, and also reduced the GA3-promoted increase of flower number. IAA reduced rachis branching and length. GA4 and benzylaminopurine (BAP) generally had similar effects to GA3 and kinetin. Some differences and responses to PGR concentrations are presented and discussed.