The proteins, sugars, organic acids and vitamins contained in fruits and vegetables are nutrients beneficial to human health. Light quality can affect the content of VC in plants by regulating the activity of VC synthesis and decomposing enzymes, and regulate the protein metabolism and carbohydrate accumulation in horticultural plants. Red light promotes the accumulation of carbohydrates, and blue light treatment is beneficial to protein formation. The combination of red and blue light has a significantly higher effect on the nutritional quality of plants than monochromatic light. Supplementing LED red or blue light can reduce the nitrate content in lettuce, supplementing blue or green light can promote the accumulation of soluble sugar in lettuce, and supplementing infrared light is beneficial to the accumulation of VC in lettuce. The supplementation of blue light can promote the increase of VC content and soluble protein content in tomato; the combined light treatment of red light and red and blue can promote the sugar and acid content in tomato fruit, and the ratio of sugar to acid is the highest under the combination of red and blue light treatment; Red and blue combined light can promote the increase of VC content in cucumber fruit.
The phenolic substances, flavonoids, anthocyanins and other substances contained in fruits and vegetables not only have an important influence on the color, flavor and commercial value of fruits and vegetables, but also have natural antioxidant activity, which can effectively inhibit or eliminate free radicals in human body. The use of LED blue light fill light can significantly increase the anthocyanin content of eggplant by 73.6%, while using LED red light, red and blue combined light can increase flavonoids and total phenol content; blue light can promote tomato red in tomato fruit The accumulation of flavonoids and anthocyanins, red and blue combined light promotes the formation of anthocyanins to a certain extent, but inhibits the synthesis of flavonoids; compared with white light treatment, red light treatment can significantly improve the flowers in the upper part of lettuce Blue pigment content, but the blue-treated lettuce has the lowest anthocyanin content in the shoots; The total phenolic content of green leaf, purple leaf and red leaf lettuce has larger values under white light, red and blue combined light and blue light treatment, but the lowest value under red light treatment; supplement LED light or orange light can increase lettuce leaves The content of phenolic compounds, while supplementing green light can increase the content of anthocyanins. Therefore, the use of LED fill light is an effective way to regulate the nutritional quality of facilities fruits and vegetables.