Growth, Nutritional Quality and Health-Promoting Compounds in Chinese Kale Grown under Different Ratios of Red:Blue LED Lights

Chinese kale (Brassica alboglabra Bailey) is one of the healthiest vegetables which is rich in health-promoting phytochemicals, including carotenoids, vitamin C, amino acid, glucosinolates, anthocyanin, flavonoids and phenolic compounds. The effects of different LEDs (white LED, 8R1B (red:blue = 8:1), 6R3B (red:blue = 6:3)) on nutritional quality in flower stalks and leaves of Chinese kale were investigated in this study. 8R1B and 6R3B were more effective than white LED light for improvement of growth and quality of Chinese kale. Flower stalk contained a higher content of nutritional compounds than leaves in Chinese kale. 8R1B significantly promoted plant growth, accumulation of biomass and soluble sugar content in flower stalks. In contrast, 6R3B significantly reduced plant dry matter, but it promoted nutritional compounds accumulation in flower stalks, such as soluble proteins, total glucosinolate, total anthocyanin, flavonoid, antioxidant activity. In addition, 6R3B enable to increase the amount of sourness and umami tasty amino acids, as well as precursor amino acids of glucosinolate. Accumulation balance of biomass and nutritional compounds is related to the ratio of red to blue light. Generally, 6R3B was more conducive to the enrichment of health-promoting compounds, as well as umami in Chinese kale.