Abstract
The effect of brief irradiation with far-red (FR) light at the end of the day (EOD-FR) on stem elongation of spray type chrysanthemums in winter was investigated with two cultivars, ‘Sei Prince’ and ‘Remidas’ in order to reduce the growing period in cut flower production. EOD-FR exposure enhanced shoot extension. Plants were grown under night break or short day conditions, with or without EOD-FR. The effect of EOD-FR under short day condition was more efficient than that under night break conditions. Under short day conditions, plants were exposed to FR light for one hour after dusk, in the middle of night, or before dawn. Exposure to FR light after dusk or in the middle of night effectively promoted stem elongation, whereas FR light exposure before dawn had little or no effect. There was no delay in flowering under any of the FR light treatments. In ‘Sei Prince’, the number of inflorescence was reduced by exposure to FR light in the middle of the night. Based on these results, it is considered that EOD-FR treatment under a short day condition is applicable to reduce the growing period efficiently by promoting stem elongation in spray type chrysanthemums.
