Effects of light intensity and spectral composition on the growth and metabolism of spinach (SPINACIA OLERACEA L.)

Abstract

Spinach rich in proteins, minerals (Fe, K) and antioxidants (vitamin C) is often cultivated in greenhouses under artificial light. In this study, the effects of light intensity and spectral composition provided by light emitting diodes (LEDs) was studied on the yield quality and quantity of spinach. Plants were grown under 3 different light intensities (100/200/300 mol m-2 s-1) and 3 spectral compositions (white/white completed with blue or far-red) for 4 weeks. Then plant weight, leaf number and area, photosynthetic activity and pigment composition of leaves were determined. The leaf quality was characterized by measurements of protein, starch, soluble sugar and ascorbate contents of leaves. Moreover, minerals (K, Fe and NO3 ̅) were also determined. While the biomass production was mainly determined by the light intensity, the yield quality is influenced significantly by the spectral composition. When the white light was supplemented with blue, high protein and ascorbate content was achieved. When far-red was added to white light, elevated sugar and Fe accumulation was observed in the leaves, while the K content decreased. In order to reach the hight quality and quantity of food production, not only the light fluence, but also the spectral composition should be regulated.

Effect of the Intensity and Spectral Quality of LED Light on Growth and Quality of Spinach Indoors

“…Ref. [11] observed similar results for ascorbate and soluble sugars in spinach. Regarding light quality, 2 R/B-treated spinach, which presented a lower FR percentage and was the only one with UV, had a higher accumulation of citrate and succinate and total carbohydrates, with no differences with the 5 R/B treatment.…”

“…Nevertheless, some challenges regarding energy efficiency, economic profitability, automation, and consumer acceptance still exist. If these challenges can be overcome, indoor vertical farming has great potential as a guaranteed source of high-quality food, providing a practical and resilient solution to present-day food system challenges [11].…”

“…In recent years, light-emitting diode (LED) technology has been developed to be more efficient and effective, having a remarkable potential as a supplemental source of light for promoting plant growth [12]. Light intensity and light quality or spectrum, through photosynthesis and the operation of photoreceptors, have broad regulatory effects on morphogenesis and many physiological and metabolic processes, which finally determine the main characteristics of plants [11].…”