INFLUENCE OF LIGHT-EMITTING DIODES ON PHENOLIC CONTENT AND ANTIOXIDANT CAPACITY LEVEL IN ROMAINE LETTUCE (LACTUCA SATIVA L. VAR. LONGIFOLIA LAM)

This research evaluated the influence of light intensity and quality in the concentration of antioxidant compounds during the production cycle of cultivated romaine lettuce under a plant-factory system. Three treatments were tested: Tl = 127.49 (red and blue), T2 = 147.32 (red and blue) and T3 = 235.69 (red, blue and supplemented white light) jimol/m2/s, respectively. The recorded variables were total concentration of phenols (TP), flavonoids (TF), non-fla-vonoid compounds (TNF), as well as antioxidant capacity by DPPH and ABTS assays. Results showed significant statistical differences among treatments and sampling events: T2 caused the highest concentration in all the variables. The concentration of antioxidant compounds in Tl and T3 was statistically equal (p ≤ 0.05). The content of total phenolics, total flavonoids and total non-flavonoids evaluated in romaine lettuce depend mainly on the incident light spectra (red and blue), which allows promotion of a significant increase (p ≤ 0.05) in concentration of 34.9, 47.9 and 29.2 %, respectively. Additionally, the red and blue light spectra in a to 3:1 ratio increase the concentration of phenolic compounds, as well as their antioxidant capacity (p ≤ 0.05).