Effects of Light Quality on the Growth and Essential Oil Content in Sweet Basil

Sweet basil seedlings were grown under four monochromatic lights irradiated with blue, blue-green, green and red LEDs that have a peak wavelength of 470, 500, 525 and 660 nm respectively. A combined white light was simultaneously irradiated by white, blue, green and red LEDs (the PPFD ratio was 3:1:1:1). The treatment conditions of the LED lights consisted of 24 +/- 2 degrees C at 50 mu mol m(-2) s(-1) PPFD. After 70 days of the light treatment, plants were harvested so as to measure their biometric characteristics and essential oil contents in leaves. The results showed that the top fresh weight, total leaf weight and total leaf area were higher under green monochromatic light than under other lights. However, the total leaf weight and total leaf area of lateral shoots were the largest under blue light. The largest amount of essential oil was observed in leaves under blue light. The essential oil contents of plants grown under blue light were 1.2-4.4 times higher than those grown under white light. On the other hand, the contents of plants grown under red light were only 12.7-77.0% of that under white light.