EFFECTS OF ORGAN EXCISION AND HORMONE APPLICATIONS ON LATERAL SHOOT EXTENSION AND INFLORESCENCE DEVELOPMENT IN CHRYSANTHEMUM MORIFOLIUM RAMAT

Abstract

SUMMARYThe excision of young inflorescence (flower) buds and young, expanding leaves from lateral shoots of pot‐grown Chrysanthemum morifolium Ramat markedly reduced internode extension. The absence of flower buds in particular restricted growth in length. The removal of more mature leaves on lateral stems had little effect. Defoliation of the main stem did not influence lateral stem length but it did delay flowering.The application of gibberellic acid (GA) more than compensated for the removal of the flower bud and/or young leaves and promoted the elongation of intact shoots. It also increased the rate of flower bud development. While indol‐3‐ylacetic acid (IAA) promoted internode extension in shoots from which flower buds and young leaves had been excised, it never significantly altered the length of intact stems and tended to delay flowering. The cytokinin 6‐benzyladenine (BAP) supplied alone induced little response. Combinations of GA and IAA, or GA and BAP, decreased internode length compared to GA alone.The data suggest that of the organs of the shoot, the flower buds and young leaves are sites of production of the hormones necessary for stem elongation and that gibberellins play the major role in promoting this process.