Construction and application of LED light formula
The growth and development of plants are significantly affected by light quality and its different composition ratios. The light formula mainly includes several elements such as light quality ratio, light intensity, and light time. Since different plants have different light requirements, and also have different light requirements at different growth and development stages, it is necessary to optimize the combination of light quality, light intensity and supplementary light time for the cultivated crops.
Light quality ratio
Compared with white light and single red and blue light, LED red and blue combined light showed comprehensive advantages on the growth and development of cucumber and cabbage seedlings. When the ratio of red and blue light is 8:2, the stem diameter, plant height, plant dryness, fresh weight, and seedling index of the plant are significantly improved, and it is also conducive to the formation of chloroplast matrix and granule lamellae and the output of assimilated products. Under the red and blue light ratio of 8:1, the cucumber seedlings had the largest plant height, stem diameter, leaf area, strong seedling index, shoot and whole plant fresh weight, and the leaves of the seedlings had higher POD and APX activities; while the red Under the blue light ratio of 6:3, cucumber seedling root activity, leaf soluble protein, soluble sugar content and net photosynthetic rate were the highest, and the SOD activity was relatively high. The use of red, green and blue light quality combination on red bean sprouts is beneficial to the accumulation of dry matter, adding green light can promote the dry matter accumulation of red bean sprouts, and the increase is most obvious when the ratio of red, green and blue light is 6:2:1. The hypocotyl elongation effect of red bean sprouts was the best under the red and blue light ratio of 8:1 treatment, and the red bean sprouts hypocotyl elongation inhibition effect was obvious but the soluble protein content was the highest under the red and blue light ratio of 6:3 treatment. When the red and blue light ratio of 8:1 is used on the loofah seedlings, the seedling index of the loofah seedlings is the largest and the content of soluble sugar is the highest. When the light quality of the red and blue light ratio is 6:3, the chlorophyll a of the loofah seedlings content, chlorophyll a/b ratio, and soluble protein content are the highest. When using the light quality with red and blue light ratio of 3:1 on celery, it can effectively promote the increase of celery plant height, petiole length, leaf number, dry matter weight, VC content, soluble protein content and soluble sugar content; in tomato cultivation, Increasing the ratio of LED blue light promotes the formation of lycopene, free amino acids and flavonoids, and increasing the ratio of red light promotes the formation of titratable acids; when the ratio of red and blue light is 8:1 to lettuce leaves, it is beneficial to its flavonoids. Carotene accumulation, and effectively reduce its nitrate content and increase VC content.
light intensity
Plants grown in low light are more susceptible to photoinhibition than those grown in high light. The net photosynthetic rate of tomato seedlings showed a trend of first increasing and then decreasing with the increase of light intensity [50, 150, 200, 300, 450, 550 mol/(m2 √)]. ) reached the maximum; the plant height, leaf area, water content and VC content of lettuce increased significantly under the treatment of 150 mol/(m2 ) light intensity, and under the treatment of 200 mol/(m2 ) light intensity, the The fresh weight, total weight and free amino acid content of the lettuce were all significantly increased, while the leaf area, water content, chlorophyll a, chlorophyll a+b and carotenoids of lettuce were all significantly increased under the light intensity treatment of 300 mol/(m2). Compared with the dark, with the increase of LED supplementary light intensity [3, 9, 15 mol/(m2)], the content of chlorophyll a, chlorophyll b, and chlorophyll a+b of black bean sprouts increased significantly, The content of VC is the highest when the light intensity is 3 mol/(m2), and the content of soluble protein, soluble sugar and sucrose is the highest when the light intensity is 9 mol/(m2). ×103 lx, (4~4.5) lx×103 lx, (6~6.5) lx×103 lx], the seedling time of pepper seedlings shortened, the content of soluble sugar increased, but the contents of chlorophyll a and carotenoids gradually decreased.
Lighting time
Appropriately extending the light time can alleviate the weak light stress caused by insufficient light intensity to a certain extent, help the accumulation of photosynthetic products of horticultural crops, and achieve the effect of increasing yield and improving quality. The content of VC in sprouts showed a trend of increasing gradually with the prolongation of light time (0, 4, 8, 12, 16, 20h/day), while the content of free amino acids, SOD and CAT activities all showed a trend of decrease; with the light time ( 12, 15, 18h), the fresh weight of Chinese cabbage plants increased significantly; the VC content of Chinese cabbage leaves and stems was the highest at 15 and 12 hours; the soluble protein content of Chinese cabbage leaves gradually decreased, but the 15h treatment the highest; the soluble sugar content of cabbage leaves gradually increased, while the stalks were the highest at 12h. In the case of red and blue light ratio of 1:2, compared with 12h light treatment, 20h light treatment reduced the relative content of total phenols and flavonoids in green leaf lettuce, but in the case of red and blue light ratio of 2:1, 20h light treatment significantly increased the relative content of total phenols and flavonoids in green leaf lettuce.
From the above, it can be seen that different light formulas have different effects on photosynthesis, photomorphogenesis, and carbon and nitrogen metabolism in different crop species. How to obtain the best light formula, light source configuration and formulate intelligent control strategies requires plant species as the starting point. , and should be properly adjusted according to the commodity demand of horticultural crops, production goals, and production factor conditions, so as to achieve the goal of intelligent control of light environment and high-quality and high-yield horticultural crops under energy-saving conditions.