Factors controlling Flowering in the Chrysanthemum

Publisher Website
Google Scholar
Abstract
Experiments are described which indicate that the annual vernalization requirement of the basal shoots of the Chrysanthemum is due to annual devernalization of these shoots as the main axis grows up and flowers. Plants sprayed with varying concentrations of maleic hydrazide were arrested in their growth for considerable periods, but this enforced ‘dormancy’ did not affect their vernalization status. This makes it appear unlikely that mere suppression of growth through apical dominance of the main shoot is the cause of this de vernalization of basal shoots. Fully or partly vernalized plants heated to 40° C. for up to 30 hours did not become dc-vernalized. Heat treatment at 35° C. for as long as 30 days also failed to achieve complete dc-vernalization, but here flowering was delayed by periods equivalent to the time spent at high temperature. However, at the end of the heat treatment progress towards flowering was resumed at the normal rate. Complete dc-vernalization can be brought about by prolonged exposure to low intensity illumination. This treatment appears to be effective right up to the stage when the first morphological changes leading to inflorescence formation take place. These results are discussed in relation to similar experiments on the de-vernalization of rye and Hyoscyamus niger.