This finding suggests a synergistic effect of blue and red light receptors in the inhibition of chrysan- themum shoot extension. Changes in light quality in the red and FR regions of the spectrum are detected by phytochromes, and phyB is the major regulator of this response(Franklin and Whitelam, 2005). In addition to red-light responses, phyA and phyB regulate various blue light-mediated physiological responses, an overlapping manner with cryptochrome(Shinomura et al., 1996; Neff and Chory, 1998; Usami et al., 2007). In the present study, the suppression of shoot extension under monochromatic blue light conditions was inhibited by supplementation with FR light(Fig. 1D). This finding suggests that shoot extension chrysanthemum is partly regulated by blue light-stimulated