Quality and accumulation level of functional substances are one of the important indicators of facility vegetable production. For vegetables, the main nutritional quality indicators include primary metabolites (sugar, protein, minerals, vitamins, cellulose, etc.) and secondary metabolites (anthocyanins, phenolics, yellows, lycopene, etc.) . These indicators are controlled by lighting conditions, and are nutritional quality indicators that can be regulated by lighting conditions, and are promising in the application of LED light sources.
Hu et al. (2014) showed that eating 200g of fruits (equivalent to two apples) per day can reduce the risk of stroke by 32%; eating 200g of vegetables per day can reduce the risk of stroke by 11%. Both the appearance quality and nutritional quality of vegetables are very important. Zheng Xiaolei et al. (2011) studied the effects of different light qualities (white fluorescent lamps, red LEDs, blue LEDs, red/blue LEDs) on the growth and burning of leaf lettuce under plant factory conditions. Efficient production provides a certain theoretical basis.
The results showed that: red/blue LEDs could significantly increase the fresh weight, leaf number and leaf area of leaf lettuce, and reduce the nitrate content of leaf lettuce, but did not reduce the edge burn disease index; red LEDs could promote stem elongation, significantly Decreased edge burn disease index and nitrate content were not conducive to dry matter, vitamin C accumulation and leaf area increase; blue LED inhibited the growth of leaf lettuce and increased nitrate content, but significantly reduced edge burn disease index. It shows that the red LED is beneficial to the growth of leaf lettuce in the plant factory and reduces the occurrence of burning edge.
Under the irradiation of red light, the internodes are longer and the stems are thinner; under the irradiation of blue light, the internodes are shorter and the stems are thicker, and the elongation growth is inhibited to a certain extent (Jao and Fang, 2003). The blue LED significantly inhibited leaf lettuce stem growth. Red light can promote stem elongation (Li and Kubota, 2009); while under blue LED treatment, the stem length is 16% shorter than the control, indicating that blue light inhibits stem elongation, and the results are consistent with previous studies .
Because blue light increases the activity of doxyacetic acid oxidase and reduces the level of auxin, which in turn inhibits the elongation and growth of plants. Compared with fluorescent lamps, red and blue LED lights can increase the vitamin C content of leaf lettuce, and red LED can significantly reduce the vitamin C content of leaf lettuce. Chen Qiang et al. (2009) found the same results in tomato.
The effect of light quality on the content of vitamin C is related to the activity of its synthesis and decomposition enzymes. Galactone dehydrogenase (GalLDH) directly catalyzes the synthesis of vitamin C from galactone; ascorbate oxidase and ascorbate peroxidase (AAP) are the key enzymes in the oxidation of vitamin C in plants (An Huaming et al., 2005). , the above three enzymes are sensitive to light. The different response mechanisms of the above three enzymes to different light qualities need to be further studied.
Vitamin C is an important nutritional component and an important indicator for evaluating the quality of leaf lettuce. Leafy vegetables are easily enriched in nitrate, which is converted into nitrite during use, which is harmful to human health. Red LED treatment can reduce the nitrate content of leaf lettuce, while blue LED treatment can increase the nitrate content of leaf lettuce (Zheng Xiaolei et al., 2011; Deng Jiangming et al., 2000).
Light environment regulation target and quality physiology of artificial light vegetable production
Quality and accumulation level of functional substances are one of the important indicators of facility vegetable production. For vegetables, the main nutritional quality indicators include primary metabolites (sugar, protein, minerals, vitamins, cellulose, etc.) and secondary metabolites (anthocyanins, phenolics, yellows, lycopene, etc.) . These indicators are controlled by lighting conditions, and are nutritional quality indicators that can be regulated by lighting conditions, and are promising in the application of LED light sources.
Hu et al. (2014) showed that eating 200g of fruits (equivalent to two apples) per day can reduce the risk of stroke by 32%; eating 200g of vegetables per day can reduce the risk of stroke by 11%. Both the appearance quality and nutritional quality of vegetables are very important.
Zheng Xiaolei et al. (2011) studied the effects of different light qualities (white fluorescent lamps, red LEDs, blue LEDs, red/blue LEDs) on the growth and burning of leaf lettuce under plant factory conditions. Efficient production provides a certain theoretical basis.
The results showed that: red/blue LEDs could significantly increase the fresh weight, leaf number and leaf area of leaf lettuce, and reduce the nitrate content of leaf lettuce, but did not reduce the edge burn disease index; red LEDs could promote stem elongation, significantly Decreased edge burn disease index and nitrate content were not conducive to dry matter, vitamin C accumulation and leaf area increase; blue LED inhibited the growth of leaf lettuce and increased nitrate content, but significantly reduced edge burn disease index. It shows that the red LED is beneficial to the growth of leaf lettuce in the plant factory and reduces the occurrence of burning edge.
Under the irradiation of red light, the internodes are longer and the stems are thinner; under the irradiation of blue light, the internodes are shorter and the stems are thicker, and the elongation growth is inhibited to a certain extent (Jao and Fang, 2003). The blue LED significantly inhibited leaf lettuce stem growth. Red light can promote stem elongation (Li and Kubota, 2009); while under blue LED treatment, the stem length is 16% shorter than the control, indicating that blue light inhibits stem elongation, and the results are consistent with previous studies .
Because blue light increases the activity of doxyacetic acid oxidase and reduces the level of auxin, which in turn inhibits the elongation and growth of plants. Compared with fluorescent lamps, red and blue LED lights can increase the vitamin C content of leaf lettuce, and red LED can significantly reduce the vitamin C content of leaf lettuce. Chen Qiang et al. (2009) found the same results in tomato.
The effect of light quality on the content of vitamin C is related to the activity of its synthesis and decomposition enzymes. Galactone dehydrogenase (GalLDH) directly catalyzes the synthesis of vitamin C from galactone; ascorbate oxidase and ascorbate peroxidase (AAP) are the key enzymes in the oxidation of vitamin C in plants (An Huaming et al., 2005). , the above three enzymes are sensitive to light. The different response mechanisms of the above three enzymes to different light qualities need to be further studied.
Vitamin C is an important nutritional component and an important indicator for evaluating the quality of leaf lettuce. Leafy vegetables are easily enriched in nitrate, which is converted into nitrite during use, which is harmful to human health. Red LED treatment can reduce the nitrate content of leaf lettuce, while blue LED treatment can increase the nitrate content of leaf lettuce (Zheng Xiaolei et al., 2011; Deng Jiangming et al., 2000).