The effects of red, blue, and white light-emitting diodes on the growth, development, and edible quality of hydroponically grown lettuce (Lactuca sativa L. var. capitata)

Abstract

Previous studies demonstrated that the combination of red (R) and blue (B) LED light was an effective light source for plant growth and development, and the light spectra, intensities, and durations can easily be controlled by growers in artificial growing environments. Therefore, the goal of this study was to investigate the influences of three different qualities of light on plant biomass and accumulation of chlorophylls (chl), carotenoids (car), soluble proteins and sugars, and nitrates in the leaves of lettuce (Lactuca sativa L. var. capitata). The marketable sensory characteristics (crispness, sweetness, shape, and color) of fresh plants were also evaluated. Plants were hydroponically cultured with a 16-h photoperiod at 24/20°C (day/night), 75% relative humidity, 900μmolmol−1 CO2 level, and 210μmolm−2s−1 photon flux density under RB LED, RB and white (RBW) LED, and a fluorescent lamp (FL, as a control) inside growth chambers for 20 days (15 days after sowing). The shoot and root fresh and dry weights as well as the crispness, sweetness, and shape of the plants treated with RBW and FL were higher than those of plants treated with RB. The soluble sugar and nitrate contents in plants grown under RBW treatment were significantly higher and lower, respectively, compared to those under RB treatment. However, the chl, car, and soluble protein contents of lettuce leaves showed no significant differences among treatments. These results demonstrate that supplemental light quality can be strategically used to enhance the nutritional value and growth of lettuce plants grown under RBW LED lights. Precise management of the irradiance and wavelength may hold promise in maximizing the economic efficiency of plant production, quality, and nutrition potential of vegetables grown in controlled environments.