Abstract
The aim of this study was to investigate the effects of green light, added with red and blue LEDs, on the growth, leaf microstructure and quality of spinach plants. Plants were transplanted and grown hydroponically for 30 days under different combinations of red:blue with a 4:1 ratio (R4B1), red:blue:green with a 5:2:3 ratio (R5B2G3) and red:blue:green with a 1:1:1 ratio (R1B1G1), at a 190 µmoL m−2·s−1 photosynthetic photon flux density (PPFD). The results showed that green light, added to red and blue LEDs at a reasonable ratio, could reduce the growth, leaf microstructure and quality of spinach plants, but not the organic acid content. The highest values for the growth parameters, photosynthetic pigments, leaf structure characteristics and quality of the spinach plant were observed for the R4B1 treatment, but not for the organic acid content. Therefore, our results suggest that green light added to red and blue LEDs at a reasonable ratio is not suitable for the growth of spinach.
Highlights
The hydroponically cultivated spinach grown under various light qualities showed significant differences in growth characteristics (Table 1)
The relative growth rate (RGR), net assimilation rate (NAR), fresh weight (FW) and dry weight (DW) of the spinach plant decreased with a decrease in the ratio of red light
The highest values of RGR, NAR and FW of the whole plant were observed in the R4B1 treatment; the lowest values of the RGR, NAR and FW for the whole plant were observed for the R1B1G1 treatment
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Light regulates a variety of plant development pathways, from germination to the induction of flowering and fruit development [1]. As an important part of the light spectrum for normal plant growth, red light affects plant morphogenesis by inducing transformations in phytochromes and is crucial in the development of the photosynthetic apparatus, as well as the regulation of the synthesis of phytochemicals such as phenolics and oxalate [2,3,4]. Blue light is effective in the stimulation of photomorphogenesis and adaptive phenomena such as the regulation of stoma opening/closing, as well as biomass accumulation and chlorophyll and anthocyanin biosynthesis [5,6,7,8,9]
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