High intensity and red enriched LED lights increased the 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.

Effect of NaCl and harvest time on antioxidant compounds and morphological cell changes in Lollo Bionda and Lollo Rosso lettuces

“…After the root emission, trays were transferred to the greenhouse and irrigated with tap water until the expanded cotyledon stage. Then, 50% of the nutrient solution used by Flores et al (2022) for leafy vegetables was used until transplant. The nutrient solution composition was (mol L -1 ): 1.25×10 -3 NH4, 11.0×10 -3 K, 4.5×10 -3 Ca, 1.0×10 -3 Mg, 19.0×10 -3 NO3, 1.125×10 -3 SO4, 2.0×10 -3 H2PO4, 40×10 -6 Fe, 5×10 -6 Mn, 4×10 -6 Zn, 30×10 -6 B, 0.75×10 -6 Cu, and 0.5×10 -6 Mo.…”

“…The plants were fastened with a low-density sponge. Two days after transplant, nutrient solution (pH 5.5 to 5.8, adjusted with nitric acid 10% solution) was added following the recommendations of Flores et al (2022).…”

“…About 30 g fresh lettuce leaves per replicate were collected and stored at -80 °C, lyophilized and crushed with an electric mill (ML-2006x, Fagor, Mondragon, Spain) until a fine powder was obtained. For the antioxidant extraction, the same method was followed as in Flores et al (2022). The methanol:water extract was stored at -20 °C in amber tubes until analysis of total phenolic, flavonoid, anthocyanin compounds and antioxidant activity.…”

“…The total phenolic concentration (TPC) was measured using the method used by Flores et al (2022); it was calculated using a gallic acid calibration curve (Merck KGaA, Darmstadt, Germany) and expressed as gallic acid equivalent (GAE) in mg 100 g -1 FM.…”

Effect of Light Intensity on the Growth and Antioxidant Activity of Sweet Basil and Lettuce

“…Light intensity affects plant development, metabolism, and the activity of the antioxidant system. The leaf area, the amount of accumulated dry mass, and the total amount of phenols are strongly dependent on the light intensity [6,[11][12][13]. To fulfill the requirements of plant growth and development, attention must be paid not only to lighting but also to balanced nutrients, as a lack of nitrogen, phosphorus, and potassium can reduce plant growth, development, photosynthesis, and leaf area.…”