Artificial light impacts the physical and nutritional quality of lettuce plants

Leafy vegetables, including lettuce ( Lactuca sativa L.), are considered to be healthy due to their high content of fiber, folate, carotenoids, phenolic and antioxidant compounds, minerals, and vitamins A, C, and K. Recently, LEDs are being used extensively as a supplementary light source in indoor agriculture due to the economical and physiological advantages that this artificial illumination offers compared to traditional fluorescence illumination. In this work, two commercially important lettuce varieties, Batavia Lettony (green leaves) and Batavia Diablotin (red leaves), were used to study the impact of LEDs (white and red–blue lights) and fluorescent illumination on their quality and health properties. Changes in the photosynthetic photon flux density from 250 to 400 µmol m −2 s −1 of fluorescent light increased growth parameters (leaf number, fresh and dry weight, and percentage of dry matter) of B. Lettony plants. We observed a positive impact of red–blue LED illumination on growth parameters analyzed in B. Diablotin plants compared to plants grown under fluorescent light at 250 µmol m −2 s −1 . Leaf texture significantly increased in B. Lettony plants grown under 400 µmol m −2 s −1 fluorescent and LED illumination compared to that of plants grown under 250 µmol m −2 s −1 fluorescent light. This variable was only increased under red–blue LED illumination in B. Diablotin plants. Accumulation of bioactive compounds, such as anthocyanins and vitamin C, was higher in B. Diablotin plants grown under 250 µmol m −2 s −1 fluorescent light. Nutrient content in the foliar part was not modified under the light conditions used, except the Ca 2+ content of B. Lettony plants grown under PPFD 400 µmol m −2 s −1 fluorescent light. Catalase (CAT) and peroxidase (POX) activities were differentially modified by light conditions in B. Lettony plants. However, POX activity was only modified in response to light conditions in B. Diablotin plants. Thus, this study demonstrates that LEDs could be used as an alternative to produce food under sustainable conditions. In this sense, although several horticultural studies have been conducted to establish the effectiveness of LEDs in lettuce growth, additional investigations are necessary to determine the optimal conditions for the use of LEDs to promote lettuce production and the accumulation of beneficial components, such as vitamins, minerals, fiber, and antioxidant compounds.