Effect of Light Intensity, Quality and Photoperiod on Stem Elongation of Chrysanthemum cv. Reagan

The effect of light quality, light intensity and photoperiod on stem elongation of chrysanthemum was studied using an image processing technique. The plant stem and internode elongation was higher in the dark than in the light, and the growth of chrysanthemum was promoted in dark period. The effect of light quality was more significant than that of light intensity and photoperiod on the growth of chrysanthemum. The growth of chrysanthemum was inhibited under blue light, and the relative elongation rate of internodes decreased with increasing intensity of blue light and irradiation duration. Chrysanthemum growth is regulated by the light condition during irradiation. This system is useful to build a model to describe the stem elongation relative to light condition for chrysanthemum, and to suggest effective production method with substitutes for chemical growth regulators.