Light Environment Optimization for Lettuce Growth in Plant Factory

Plant factory is a crop production system which is isolated from outside environment. Fluorescent lamp is popularly used in the plant factory, however, the spectrum of fluorescent light is broad and some portion of them is not necessary for photosynthesis. On the other hand, LED (light emitting diode) has narrow band width and is getting common these days. The final goal of this project was to develop a new light apparatus with LEDs optimized for vegetable production in plant factory. The specific objective was to investigate the effective light quality for growing plant more healthy and rapidly. The effect of light provided by various light qualities provided by the combination of LEDs(blue, green, red) on the photosynthesis rate, growth and morphogenesis of lettuce (Lactuca sativa L “Greenwave”.) were evaluated and the response compared with those of plant irradiated by fluorescent lamps. Photosynthesis rate of lettuce was greater in monochromic red light and the mixed light with red and blue LEDs. Stem length increased in monochromic red and blue light and decreased in mixed light. Fresh weight of lettuce was increased in monochromic red and fluorescent light.