Flower and Leaf Initiation byChrysanthemum MorifoliumRamat in Long Days

Abstract

Rooted cuttings of twelve cultivare of Chrysanthemum morifolium, a short-day plant, were grown exclusively in long days in three consecutive experiments. The terminal and axillary apical meristems of all cultivars eventually initiated flower buds, although their further development was inhibited in long days and they did not reach anthesis. The period of vegetative growth was quantified in terms of the numbers of leaves and bracts initiated by each meristem prior to flower initiation. This number varied between cultivars and between experiments, but when the cultivars were ranked in order of leaf number, their relative positions were similar in each experiment. The rate of leaf initiation also varied between cultivars, but was not correlated with the number of leaves formed below the flower, from which it was estimated that the time of flower initiation also varied with cultivar. It was concluded that flower initiation in the chrysanthemum in long days is inevitable, with the time of initiation depending on the genetic constitution of each cultivar and related in some way to an aging process that occurs in each apical meristem.