AsianScientist (May 17, 2016) – Researchers in China and the UK have found that hydroponic lettuce grown under light-emitting diodes (LEDs) have lower nitrate levels and enhanced free-radical scavenging ability. Their findings, published in Journal of the American Society for Horticultural Science, suggest that continuous exposure to LED light could be used to improve lettuce quality.
Increasingly, vegetables are being grown using efficient, soil-less techniques such as hydroponics. Hydroponic systems are favored for their ability to improve water and nutrient use efficiency and crop yields, and have the added benefit of allowing growers to use fewer chemical fertilizers.
“Vegetables, especially leaf vegetables, grown in hydroponics can accumulate high levels of nitrate and other harmful substances,” explained corresponding authors Professor Yang Qi-Chang from the Institute of Environment and Sustainable Development in Agriculture, Chinese Academy of Agricultural Sciences, and Professor Lu Chungui from Nottingham Trent University.
They added that previous research on the effects of continuous light on photosynthesis and plant growth has mainly focused on the circadian clock and induced injury. Less is known about the effect of continuous LED light on the response of the photosynthetic system and on changes in the concentrations of antioxidant substances and phytochemicals.
The research team designed experiments with continuous light (CL) and/or a combination of green (G) with red-blue (RB) LED light to determine whether the treatments could decrease nitrate content and increase nutrient contents in hydroponically grown lettuce. The experiments included white LED light and combined red-blue LED light (with or without green LED light) in five variations.
“Our results clearly showed that continuous light by RB and RBG LED dramatically affects the nitrate content of lettuce at preharvest stage,” the authors said. “Nitrate content reduced dramatically under both RB-CL and RBG-CL treatments between zero and 24 hours.”
Results also demonstrated that RB LED light was more effective than white LED light in facilitating lettuce growth.
“Continuous LED light for 24 hours significantly enhanced free-radical scavenging activity and increased phenolic compound concentrations,” the authors said.
They recommended treatments of 24 hours of continuous RB LED with G light exposure to decrease nitrate content and enhance lettuce quality.
The article can be found at: Bian et al. (2016) Continuous Light from Red, Blue, and Green Light-emitting Diodes Reduces Nitrate Content and Enhances Phytochemical Concentrations and Antioxidant Capacity in Lettuce.
Source: American Society for Horticultural Science; Photo: Jay & Melissa Malouin/Flickr/CC.
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