Inhibition of flowering and growth in Pharbitis nil by the growth retardant Ancymidol

Abstract

Flower formation and growth of the short day plant Pharbitis nil, strain “Violet”, were inhibited when the growth retardant Ancymidol was applied prior to an inductive dark period via cotyledons or roots. Inhibition of flower formation by Ancymidol could be completely reversed by an application of gibberellin A₃ (GA₃) to the plumule before the inductive dark period. A dose of 0.01 μg GA₃/plant was almost sufficient to restore flowering, but about a hundred times more GA₃ was required to restore the internode length to that of control. Ancimidol greatly reduced the endogenous gibberellin content.