Effect of laser-diode light on growth of Lactuca sativa L.

Development of an effective, high-power, low-cost, artificial light source for use in plantgrowing facilities would be very beneficial for plant production. Recently, the laser-diode lamp has been proposed as a new type of light source for plant production. The advantages of the laser-diode lamp over conventional light sources are its high electrical-to-optical power conversion efficiency, low thermal radiation, easy set-up for high power and pulse irradiation, small weight and small volume for mounting, and selectivity for proper wavelength. Because laser light itself differs from the light sources presently used in plant growing, we confirmed the possibility of growing plants under the laser-diode light by growing lettuce (Lactuca sativa L.) plants. Lettuce seedlings with 5-6 leaves were grown under a laser-diode lamp panel with 30 pieces of high-power and high-efficiency AlGaInP laser-diodes. The power of each laser-diode lamp was 500 mW, and the wavelength was 680 nm, which was efficient for photosynthesis. The lettuce plants were able to grow under the laser-diode light. However, the weight of the lettuce plants grown under the laser-diode lamps was light, and their leaves were long and thin compared to those of lettuce plants grown under high-pressure sodium lamps.