Effects of the Growth Retardant CCC on Floral Initiation and Growth in Pharbitis nil

Abstract

Growth-retarding chemicals such as Amo-1618 (2, 12), CCC [(2-chloroethyl) -trimethyl-ammonium chloride] (2, 11), and Phosfon D (2) reduce the height of many plants, leaving, in most cases, flowering and fruiting unaffected. Thus, of 55 species studied by Cathey and Stuart (2) control of flowering by photoperiod and temperature was unaffected by application of growth retardants. Flowering was delayed by such applications only in the cases of Chrysanthemum and Cleome. In the day-neutral plant tomato Wittwer and Tolbert (13) found that flower clusters in CCC-treated plants appeared earlier and on lower nodes. Application of both CCC and Phosfon caused prompt initiation of flower buds in Rhododendron (10). On the other hand, floral initiation as induced by shift from long to short days in the long-short-day plant Bryophyllum daigrernontianum was fully suppressed by application of CCC (16). The CCCrelated compound, allyl trimethylammonium bromide, reduced stem elongation and flower formation in the cold-requiring rosette plant Beta vulgaris (6). Inhibition of flowering in both Bryophyllum and Beta could be overcome by application of gibberellin A3. No specific effects of growth retardants on floral initiation in short-day plants (SDP) have heretofore been reported. The present paper concerns the effects of the growth retardant CCC on flower formation and growth of the SDP Pharbitis nil and the reversibility of these effects by gibberellin A3.