Effect of green light wavelength and intensity on photomorphogenesis and photosynthesis in Lactuca sativa

In this study, the effects of green light-emitting diodes (LEDs) with different peak wavelengths and light intensities on lettuce growth and photosynthesis were evaluated. The green LEDs used were G510 (peak wavelength: 510 nm; band width at half peak height: 18 nm), G520 (524 nm; 30 nm) and G530 (532 nm; 36 nm) at a photosynthetic photon flux (PPF) of 100, 200 and 300 mu mol m(-2) s(-1), respectively (maximum output of G530 was PPF 260). Shoot and root growth in lettuce plants irradiated with green LED light at PPF 100 decreased compared with white fluorescent light, but root growth of plants irradiated with green LED light at PPF 200 increased, and shoot growth of plants grown under G510 at PPF 300 was the highest of all light sources. Leaf photosynthetic rate (Pn) of plants irradiated with green LED light at PPF 200 was dramatically higher than that at PPF 100, and the Pn of plants irradiated with G510 was the highest of all light sources. These results indicated that high-intensity green LED light was effective to promote plant growth and, in particular, short-wavelength green light was available for active plant growth. (C) 2011 Elsevier B.V. All rights reserved.