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 in a greenhouse in Dallas, Texas.

Red leaf lettuce (Lactuca sativa L. ‘Red Mist’) plants grown in a hydroponic system were treated with daytime or nighttime SL with red (R) and blue (B) LEDs (RB-LED), blue and UVA LEDs (B/UVA-LED), or white LEDs (W-LED) for three days before harvest and compared to those without SL (control). All SL treatments provided a photon flux density of 167 μmol·m−2·s−1 for 12 h daily. Compared with the control, SL treatments increased leaf thickness and greenness, antioxidant capacity, and concentrations of phytonutrients such as anthocyanins, carotenoids, and total phenolics; however, shoot fresh biomass and total leaf area were generally not affected by SL.

There were no differences in all of the above traits among W-LED, RB-LED, and B/UVA-LED. Compared with daytime SL, nighttime SL increased leaf greenness and carotenoid concentration. In summary, all three LEDs with different spectra were effective in improving lettuce quality as short-term pre-harvest SL sources, and nighttime SL was more effective than daytime SL; however, plant fresh weight and total leaf area were not affected.

Read the complete research at

Hooks, Triston & Sun, Ling & Kong, Yun & Masabni, Joseph & Niu, Genhua. (2022). Short-Term Pre-Harvest Supplemental Lighting with Different Light Emitting Diodes Improves Greenhouse Lettuce Quality. Horticulturae. 8. 435. 10.3390/horticulturae8050435. 

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