High intensity and red enriched LED lights increased growth of lettuce and endive

Abstract

Changes in plant responses have been associated with different fractions of the visible spectrum and light intensity. Advances in light emitting diodes (LED) have enabled the study of the effect of narrow wavelengths on plant growth and antioxidant compound synthesis. LED technology also facilitates the incorporation of light sources in a controlled setting where light spectra and intensity can be regulated. The objective of this study was to compare the effect of two commercial light spectra (S1: standard white light with 32.8% blue, 42.5% green, 21.7% red and 2.4% far red;S2: AP67 spectrum, designed for horticultural growth, with 16.9% blue, 20.5% green, 49.7% red and 12.3% far red) at two light intensities [LI: low intensity (78 µmol·m-2s-1 of photons for S1 and 62 µmol·m-2s-1 for S2, and HI: high intensity (102 and 100 µmol·m-2s-1 for S1 and S2, respectively)] on growth and antioxidant compound contents in two leafy vegetables: endive (Cichorium endivia L.) and lettuce (Lactuca sativa L.). Fresh weight (FW), dry weight (DW), and DW% of plants were taken as growth indicators. Leaf number, SPAD index, leaf area (LA) and specific leaf area (SLA) were also evaluated. Antioxidant synthesis was measured as total phenol content (TPC), total flavonoid content (TFC) and antioxidant activity (AA). The results showed that S2 and HI increased the FW, DW, and LA in both species. On the other hand, antioxidant compound contents were significantly increased by HI but did not vary with the spectrum.

Keywords

• LED
• indoor growth
• leafy vegetables
• phenolic compounds
• vertical farming.