EFFECTS OF IRRADIANCE AND TEMPERATURE ON FLOWERING OF CHRYSANTHEMUM-MORIFOLIUM RAMAT IN CONTINUOUS LIGHT

The short-day plant Chrysanthemum morifolium cv. Polaris initiated flower buds in all irradiances of continuous light from 7.5 to 120 W m-2. As the irradiance increased, the transition to reproductive development began earlier and the number of leaves initiated before the flower bud was reduced. The autumn-flowering cultivars Polaris and Bright Golden Anne, and the summer-flowering Golden Stardust were also grown in continuous light at different temperatures; all initiated flower buds at temperatures from 10 to 28 °C but only the buds of Golden Stardust developed to anthesis and then only at 10 and 16°C. Flower initiation began earliest at 16-22 °C, and the number of leaves formed before the flower bud was increased at 28°C. Golden Stardust was exceptional in that the number of leaves formed was also increased at 10 °C. Axillary meristems adjacent to the terminal meristem initiated flower buds rapidly at 10 °C but not at 28 °C in all three cultivars. These results are discussed in relation to the autonomous induction of flower initiation and the effects of the natural environment on flowering of chrysanthemum. © 1979, Annals of Botany Company.