1790 Y. Higuchi et al. /Journal of Plant Phy The effects of light quality on the regulation of flowering vary according to plant species. In general, LDPs require a long daily period of exposure to light, followed by a short period of exposure to FR light, to promote flowering. Furthermore, blue light promotes flowering in cruciferous species(including Arabidopsis), but gen- erally has low effectiveness in other LDP families(Thomas and Vince-Prue, 1997; Runkle and Heins, 2001). In contrast to LDPs, short-day plants(SDPs) are less sensitive to the quality of light applied during different parts of the light period, but require a long period of exposure to darkness. Thus, the majority of LDPs and SDPs are also classified as light-dominant and dark-dominant plant,respective.