Abstract
To reduce the energy consumption involved in greenhouse heating, we investigated the effect of short-term rising temperature treatment performed around the end of the day (referred to hereafter as “EOD-heating treatment”) on the growth, flowering, and cut-flower quality of spray-type chrysanthemums. We used EOD-heating treatments for the 2 chrysanthemum cultivars ‘Sei-prince’ and ‘Remidas’ at 3 growth stages: vegetative growth, flower bud differentiation, and flower bud development. The EOD-heating treatments performed in the vegetative growth stage did not negatively affect the cut-flower quality, but the shoot extension growth was slightly suppressed during the lowest-temperature regime (17°C for 3 hours after dusk and maintained at 9°C thereafter). The following EOD-heating treatments were found to be practical to implement in the flower bud differentiation and flower bud development stages: (1) 20°C for 7 hours after dusk and maintained at 13°C thereafter; and (2) 17°C for 3 hours after dusk and maintained at 11°C thereafter. On comparing the treated with the control plants, it was found that these treatments did not negatively affect the days to flowering and cut-flower quality. The effect of EOD-heating treatment on flowering and cut-flower quality was investigated for all growth stages in the case of 21 cultivars. For 8 cultivars, the days to flowering were the same as those for the control. For 11 cultivars, the flowering was slightly delayed, and the days to flowering were 3 days longer than those for the control. For 18 cultivars, the cut-flower quality was equal to or better than that for the control. On the basis of these results, it is considered that EOD-heating can help reduce the energy consumption involved in greenhouse heating for spray-type chrysanthemum production during winter.
