Effects of light sources, light quality on the growth response of red and blue leaf lettuce in closed-type plant factory system
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The light treatments were composed of red, blue, white, far-red, red+far-red, red+blue, red+blue+white LEDs and duty ratio(%) of mixed light red+blue (100, 95, 90, 85, 80, 75), red+blue+white (100, 85, 70). The following results were obtained in different LED light sources treatment: Red leaf lettuce’s leaf number were the most under white LED. Leaf size was the highest under red+blue LEDs and shoot length was the longest under red+far-red LEDs. Shoot were the heaviest under red LED. Blue leaf lettuce’s leaf number and shoot length were high under all light treatment except far-red LED. Each vertical and width length of leaves were the longest under red+blue LEDs, white LED. Leaf number of red leaf lettuce were more in 85%-100% duty ratio than in 75, 80% duty ratio and leaf size was highest in 100% duty ratio under the mixed light red+blue LEDs. Shoot length was the highest in 90% duty ratio. Blue leaf lettuce’s leaf number and shoot length showed no difference in LED light treatment. Leaf size was the highest in each 100, 95%. Shoot and root biomass were highest in 95%. Shoot length of red leaf lettuce was the highest in 70% duty ratio nunder the mixed light of red+blue+white. The others showed no difference in duty ratio. Blue leaf lettuce’s leaf number, shoot length and biomass were the highest in 85% duty ratio. Thus, we can cultivate stably without reference to external factors, if we use appropriate light sources and light quality in closed-type plant factory.