Effects of Supplemental Green LEDs to Red and Blue Light on the Growth, Yield and Quality of Hydroponic Cultivated Spinach (Spinacia oleracea L.) in Plant Factory

Abstract

The effect of three different light qualities on growth, photosynthesis, quality and safe parameters of hydroponic cultivated spinach (Spinacia oleracea L.) were investigated indoor. Three different light qualities were created of red (660 nm), blue (450 nm) and green (550 nm) LEDs corresponding at ratio R660/B450 = 4/1 (RBL); R660/B450/G550= 5/2/3 (WWL); R660/B450/G550 = 1/1/1 (WL), which were tested at the same intensity (PPFD =190 µmol m-2 s-1). The results showed that the plant height and leaf number were the lowest in WL treatment. The SPAD, Net photosynthesis rate Pn, Fv/Fm, Leaf area index LAI values and all parameters of root characteristics were the highest in RBL treatment and were significantly different from two others. Fresh weight of stem, leaf and root, dry weight of root in the three light qualities were significantly different. In contrast, the highest K + content in WL was different from WWL and RBL treatments, while Ca 2+ and Fe 2+ content were the highest in the RBL treatment. Vitamin C content was significantly different between the three treatments. nitrate and oxalic acid contents were the highest in WL treatment, whereas soluble-solids contents and vitamin C contents were the highest in RBL treatment. Oxalic acid, nitrate contents were observed tending reduced under WWL although oxalic acid content in RBL treatment was not different from WL and WWL treatments. In all three different light treatments were not detected Salmonella, E.coli. Our results suggest that RBL may be appropriate light for growth of spinach, but supplementary green light to a combination of red and blue LEDs at the reasonable rate can change the quality of spinach in a positive direction. Hydroponic cultivated spinach was safe for users.

Effect of Different Monochromatic LEDs on the Environmental Adaptability of Spathiphyllum floribundum and Chrysanthemum morifolium

“…This phenomenon was similar with the research by Farquhar [ 66 ], and it may be due to a decrease in the photosynthetic activity of mesophyll cells. Most studies have found that plant leaves absorb very little green light, so green light is often considered ineffective for plant photosynthesis and not conducive to plant growth [ 16 , 24 , 25 , 26 ]. However, relevant studies have shown that green light can affect the proportion and state of light distribution in plant leaves, participating in the regulation process of photosynthesis [ 67 , 68 , 69 ].…”

“…Red light not only drives photosynthesis but also induces stem elongation, soluble sugar synthesis, and changes in photosynthetic apparatus [ 1 , 8 , 15 ]. The underlying mechanisms of green and ultraviolet (UV) wavelengths might still require further investigation; however, they have been studied significantly in recent years [ 16 , 17 ]. Two bands of UV light, UV-B (280–320 nm) and UV-C (100–280 nm), induce the production of free radicals, which can destroy plant DNA, proteins, lipids, chloroplasts, and photosynthetic pigments [ 18 , 19 ] and can inhibit plant photosynthesis and growth [ 18 , 20 , 21 ].…”

Influence of Green Light Added with Red and Blue LEDs on the Growth, Leaf Microstructure and Quality of Spinach (Spinacia oleracea L.)

“…This experiment was conducted in an indoor system at the Institute of Agrobiology, Vietnam National University of Agriculture. These methods draw upon our previous work [33,34]. The room temperature and humidity were maintained at 27 ± 0.5 • C and 65 ± 5%, respectively.…”

Comparative evaluation of the photosynthetic photonic efficiency of white LEDs

“…Research results are sometimes quite contradictory. Thus, some varieties of lettuce and spinach show great productivity when lamps with red-blue LEDs are used [11][12][13][14], in some cases the results do not differ significantly [15][16][17].…”