Urbonaviciute et al. (2007) studied the effects of 92% LED red light (640nm) + 8% near-ultraviolet light, 86% LED red light + 14% LED blue light, 90% LED red light + 10% cyan light on lettuce with fluorescent lamps as a control. Growth and effects of nitrate content.
The sugar content of 86% LED red light + 14% LED blue light treatment was significantly higher than the other two combinations, and also significantly higher than the control, but the sugar content of the other two combinations was significantly lower than the control. The nitrate content in all three treatments was 15%-20% lower than the control. Red light plays a key role in stimulating nitroreductase, and the combination of red and blue light enhances nitrogen absorption and assimilation in plants.
Nitrate can be reduced by more than 20% through light quality optimization, but there is no significant difference in nitrate content among the three combinations, indicating that red light may play the main role in reducing nitrate.
It can be seen from Table 1-1 that the AsA content of the tested leaf lettuce varieties treated with LED red light was significantly lower than that of the control, and LED blue light and LED red and blue light had no effect on the AsA content. Compared with the control, LED red light treatment significantly reduced the nitrate content of the tested leaf lettuce varieties, but LED blue light had no effect on the nitrate content in lettuce. Compared with the control, the test varieties treated with LED red light reduced the calcium content in the leaves, but the difference was not significant. The calcium content in the leaves of leaf lettuce reached the maximum value under the LED blue light treatment, which was significantly higher than that of the control, while there was no difference between the red and blue light LED treatment of the calcium content in the leaves of the tested varieties and the control. Different LED light quality had no significant effect on the total magnesium and total potassium content of leaves (Zheng Xiaolei et al., 2011).
Samuoliene et al. (2011) studied the effect of LED supplementary light on three lettuce varieties grown in a greenhouse under a high pressure sodium lamp (16-h). 3d before harvest, 638nm 300umol/m2·s LED red light was used for 16h. This pre-harvest treatment significantly reduced the nitrate content in red and green leaf lettuce by 56.2% and 20.0%, respectively, but increased Light green leaf lettuce varieties had 6 times as much nitrate.
LED supplemental light treatment increased the total phenolic content (52.7% and 14.5%) and free radical removal capacity (2.7% and 16.4%) in red and light green lettuce, but decreased in green lettuce. Only the AsA content in red lettuce was significantly increased (63.3%) after treatment. The authors believe that red light affects the expression of antioxidant capacity of lettuce, revealing the effect of light quality on the physiological and metabolic processes of plants. However, the effect of red light supplementing light varies from variety to variety, and the sensitivity of each variety to light environment is affected by the presence of antioxidants in lettuce leaves. is determined by the accumulation level in .
Effect of LED Grow Light Quality on Nitrate Content（二）
Urbonaviciute et al. (2007) studied the effects of 92% LED red light (640nm) + 8% near-ultraviolet light, 86% LED red light + 14% LED blue light, 90% LED red light + 10% cyan light on lettuce with fluorescent lamps as a control. Growth and effects of nitrate content.
The sugar content of 86% LED red light + 14% LED blue light treatment was significantly higher than the other two combinations, and also significantly higher than the control, but the sugar content of the other two combinations was significantly lower than the control. The nitrate content in all three treatments was 15%-20% lower than the control. Red light plays a key role in stimulating nitroreductase, and the combination of red and blue light enhances nitrogen absorption and assimilation in plants.
Nitrate can be reduced by more than 20% through light quality optimization, but there is no significant difference in nitrate content among the three combinations, indicating that red light may play the main role in reducing nitrate.
It can be seen from Table 1-1 that the AsA content of the tested leaf lettuce varieties treated with LED red light was significantly lower than that of the control, and LED blue light and LED red and blue light had no effect on the AsA content. Compared with the control, LED red light treatment significantly reduced the nitrate content of the tested leaf lettuce varieties, but LED blue light had no effect on the nitrate content in lettuce. Compared with the control, the test varieties treated with LED red light reduced the calcium content in the leaves, but the difference was not significant. The calcium content in the leaves of leaf lettuce reached the maximum value under the LED blue light treatment, which was significantly higher than that of the control, while there was no difference between the red and blue light LED treatment of the calcium content in the leaves of the tested varieties and the control. Different LED light quality had no significant effect on the total magnesium and total potassium content of leaves (Zheng Xiaolei et al., 2011).
Samuoliene et al. (2011) studied the effect of LED supplementary light on three lettuce varieties grown in a greenhouse under a high pressure sodium lamp (16-h). 3d before harvest, 638nm 300umol/m2·s LED red light was used for 16h. This pre-harvest treatment significantly reduced the nitrate content in red and green leaf lettuce by 56.2% and 20.0%, respectively, but increased Light green leaf lettuce varieties had 6 times as much nitrate.
LED supplemental light treatment increased the total phenolic content (52.7% and 14.5%) and free radical removal capacity (2.7% and 16.4%) in red and light green lettuce, but decreased in green lettuce. Only the AsA content in red lettuce was significantly increased (63.3%) after treatment. The authors believe that red light affects the expression of antioxidant capacity of lettuce, revealing the effect of light quality on the physiological and metabolic processes of plants. However, the effect of red light supplementing light varies from variety to variety, and the sensitivity of each variety to light environment is affected by the presence of antioxidants in lettuce leaves. is determined by the accumulation level in .