Short-Term Pre-Harvest Supplemental Lighting with Different Light Emitting Diodes Improves Greenhouse Lettuce Quality

Winter–spring greenhouse vegetable production is limited by low-level natural light, resulting in decreased growth and quality. To investigate whether short-term pre-harvest supplemental lighting (SL) with light emitting diodes (LEDs) can address this issue, a study was conducted Dallas, Texas. Red leaf lettuce (Lactuca sativa L. ‘Red Mist’) plants grown hydroponic system were treated daytime or nighttime SL red (R) blue (B) LEDs (RB-LED), UVA (B/UVA-LED), white (W-LED) for three days before harvest compared to those without (control). All treatments provided photon flux density of 167 μmol·m−2·s−1 12 h daily. Compared the control, increased thickness greenness, antioxidant capacity, concentrations phytonutrients such as anthocyanins, carotenoids, total phenolics; however, shoot fresh biomass area generally not affected SL. There no differences all above traits among W-LED, RB-LED B/UVA-LED. SL, greenness carotenoid concentration. In summary, different spectra effective improving quality sources more than SL; plant weight affected.