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 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.