Effect of supplemental blue light intensity on the growth and quality of Chinese kale

The influence of blue light on the growth and quality of vegetables is controversial, since both positive and negative effects have been observed on different varieties of vegetables and most research has been conducted with a combination of light spectrums. In this work, we investigated the effects of supplemental blue light intensity on growth, nutritional quality, and health-promoting compounds of Chinese kale (Brassica alboglabra Bailey) using only blue (460 nm) light-emitting diodes 10 days before harvest in a greenhouse under ambient light conditions. Four blue-light treatments were conducted (0, 50, 100, and 150 μmol m−2 s−1, named T0, T50, T100, and T150, respectively) with 12 h (6:00–18:00) of light treatment per day. The growth of Chinese kale plants was improved by supplemental blue light. The fresh and dry weights of Chinese kale plants were significantly higher under T50 and T100 than those in the other treatments. The content of chlorophyll b and total chlorophyll increased significantly under T50, and the content of carotenoids increased significantly under T150. The contents of soluble sugars and free amino acids were significantly increased under the blue light treatments. The nitrate content decreased with increasing blue light intensity, while the anthocyanin content increased. The contents of vitamin C in T50 and total phenolic compounds in T150 were significantly higher than in T0. The flavonoid contents were significant higher in T50 and T150, and significantly lower in T100. Our results show that blue light can influence the growth and quality of Chinese kale and 50 μmol m−2 s−1 of supplemental blue light might be the most feasible light intensity for Chinese kale production.