Different ratios of red and blue LEDs enhance Romaine lettuce production and antioxidant capacity in urban controlled environment

Light is an important factor for plant growth especially in controlled environment. Different wavelengths initiate morphological and biochemical changes in plants. The objective of this study was to examine the effect of different LEDs on the vegetative growth and antioxidant capacity in lettuce and to compare the responses with fluorescent light (FL). Four treatments were tested: FL (white fluorescent light), 100% red LEDs, 19:1 and 10:1 red (R) to blue (B) LEDs. Romaine lettuce (Lactuca sativa L.) were cultured with FL and the different LEDs in growth chambers with a temperature of 25±2.5°C, ambient CO₂, and a 16 h light, 8 h dark photoperiod for five weeks. Lettuce plants grown under the various ratios of R and B LEDs showed increased leaf number, fresh mass, dry mass and antioxidant capacity compared to pure R (100%) and FL. Significantly higher antioxidant accumulation was observed in plants cultivated under 10:1 R to B ratio LEDs compared to 100% R and FL. The lowest biomass (fresh mass and dry mass) and antioxidant accumulation were observed in 100% R LED. This research will enhance knowledge for selecting the appropriate LEDs for antioxidant rich crop production.