Effects of Night-break Light Quality on Floral Inhibition of Chrysanthemum

Effects of the wavelength of night-break light on the inhibition of flower bud differentiation in chrysanthemum were investi-gated using the cultivars ‘Arajin2’ and ‘Iwanohakusen’. Wavelengths of 516, 593, 630, 663, 684, and 705 nm of light were produced using LED lamps. Effective wavelengths for inhibition in both ‘Arajin2’ and ‘Iwanohakusen’ were 593, 630, and 663 nm, and the most effective wavelength was 630 nm in ‘Arajin2’ and 593 and 630 nm in ‘Iwanohakusen’, respectively. The effectiveness of red light or a mixture of red and far-red light as a night-break light was compared using ‘Arajin2’ and ‘Iwanohakusen’. No difference in the inhibition of flower bud differentiation was observed in ‘Arajin2’, whereas the mixed light of red light and far-red light was more effective than red light to inhibit flower bud differentiation of ‘Iwanohakusen’.