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

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-2s -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.