Effects Of Proprotions Of Red And Blue Light On Physiological Characteristics And Quality In Leafy Greens

Lettuce (Lactuca sativa L), belongs to lettuce genus of compositae, annual or biennial herbaceous crops, is an important green leafy vegetables.In recent years it becomes one of the main types of facilities vegetables. Pakchoi (Brassica campestris ssp. chinensis Makino), also known as Chinese cabbage, is an annual herbaceous plant, leafy veggies, dark green color. In vegetable cultivation, the facility is easy to form low-light environments, especially in autumn and winter, light intensity weakened, sunshine time is short, with insulation covering equipment within the facility often makes insufficient light, so low light conditions become obstacles to the growth of vegetables, seriously affect the yield and quality of vegetables. Thus, good regulating greenhouse light environment is the primary condition for achieving high yield and quality of greenhouse crops. Light Emitting Diode (LED) is a solid-state semiconductor devices, which can directly convert electrical energy into light, artificial light compared with other conventional incandescent, fluorescent, high pressure sodium lamp, LED has a low voltage, energy-efficient, light narrow, small size, long life and other advantages, LED has been widely used in modern agriculture.In this paper, using lettuce and pakchoi as materials, LED as the lighting equipment, we studied the effects of different proportions of red and blue combination light on Pakchoi growth. The main results are as follows:l.The study investigated the effects of light qualities on seed germination and seedling growth of lettuce. Plants were grown under six different combinations of red and blue light (2R/1B?4R/1B?8R/1B?1R/2B?1R/4B?1R/8B). The results showed that different light qualities have different influences on seed germination and seedling growth of lettuce. (1) The combination of red (R) and blue (B) lights based on red promoted seed germination obviously, and the germination potential, germination index and vigor index under these treatments were significantly higher than those of control. (2) Compared with W-grown seedlings, the mixture of blue and red light promoted the morphogenesis, root activity, content of leaf pigment and chlorophyll fluorescence of lettuce seedlings. Furthermore, the promoting effects under the RB lights based on red were better than those of treatments based on blue. (3)The combination of 2R/1B and 4R/1B were better than the combination of 8B/1R on promoting seed germination and seedling growth in lettuce. These results indicated that light quality significantly affected the seed germination and seedling growth of lettuce, and the treatments of 2R/1B and 4R/1B showed more superiority than others.2. The red and blue composite light can improve the green chlorophyll content, net photosynthetic parameters and chlorophyll fluorescence parameters, and then promote the pakchoi growth and development. Among them, the combination of red (R) and blue (B) lights based on red is better than based on blue in promoting the fresh weight, dry weight, leaf area, chlorophyll content, stomatal parameters and chlorophyll fluorescence parameters of pakchoi. But the vegetables in the treatment based on blue have higher shoot ratio and root activity, photosynthetic systems for stronger protection. Under 4R/1B and 8R/1B processed pakchoi more vigorous shoot growth, fresh weight, dry weight, and larger, larger leaf expansion, commodity traits better; under 1R/4B processing, maximum root activity, root to shoot ratio is higher than control, robust vegetables seedlings.3. The pakchoi treated by combination of red and blue lights based on red has higher soluble sugar content, and the treatment of 8R/1B promoting effect is most obvious, with 74.67% higher than that of control; Based on blue is beneficial to the formation of soluble protein, vitaminC, carotenoid, flavonoid and total phenol.Different nutritional quality has different responses to light quality. Soluble protein content was the highest under the treatment of 1R/4B, with 19.48% higher than the control. The vitamin C and carotenoid content were highest in the treatment of 1R/8B,14.45% and 27.57% higher than that of the control, flavonoids and total phenolic content obtained the maximum at 1R/2B treatment with 19.12% and 11.20% higher than that of the control.4. Different proportions of red and blue complexes light have different regulatory role on the antioxidant enzymes and metabolic enzymes activity of pakchoi.The combination of red (R) and blue (B) lights based on blue have promoting effect on the activities of SOD, POD, CAT, APX. But the combination lights based on red have the opposite processing, the activities are lower than that of control.1R/8B treatment has the most significant effect, and comparing with the control, SOD, POD, CAT and APX under the treatment of 1R/8B increased by 32.56%,19.82%,32.38 and 14.07%. Red and blue composite light promoted the PAL activity, in which 8R/1B promoting effect is most obvious, higher than the control 51.72%; under 1R/2B and 2R/1B handling PPO was increased by 17.84% and 9.32%, and the other dealing with no significant difference compared with the control.5. Different peaks of red light complexed with blue light with different proportions can better promote the growth and quality formation of pakchoi. When the ratio of red and blue light is 4/1, the indicators of fresh weight, dry weight and chlorophyll content of plant are maximum.The root activity decreased with the increase of the proportion of red light. When the ratio of 660 nm red and blue is 8/1, soluble sugar content is the highest, while the ratio of 630 nm red with blue is 12/1. Except that the flavonoid content under A (8/1) treatment is less than B (8/1), the other combinations using 630nm red light is no less than that of 660nm. In the ratio of (4/1),there is no significant difference in two peaks in many indicators, so we can use 630 nm red light instead of 660 nm red light in this ratio.