Abstract
Night-break (NB) treatment inhibits flowering in short-day plants and is widely used in the flower production of cut chrysanthemum (Chrysanthemum morifolium Ramat.). Light-emitting diode (LED) lamps have been replacing incandescent lamps owing to energy savings. Previous studies on chrysanthemum under NB treatment with LED lamps raise the possibility of varietal difference in floral differentiation ability. Therefore, this study evaluated the effects of NB treatment using LED lamps with several wavelengths on 12 chrysanthemum cultivars. NB treatments at 630-, 660-, and a combination of 660- and 735-nm LEDs inhibited floral differentiation in all cultivars. However, the effects of NB treatments with 690- and 735-nm LEDs differed among cultivars. Some cultivars showed inhibited floral differentiation with both 690- and 735-nm LED NB treatment, whereas others were scarcely affected. Meanwhile, NB treatment with a combination of 660- and 735-nm LEDs had the most stabile inhibitory effect on floral differentiation among chrysanthemum cultivars.
