What are the main effects of LED light on Plants Growth?

effects of LED light on Plants Growth -

What are the main effects of LED light on Plants Growth?

Red Light
In the visible light, the most absorbed by green plants are red orange light (wavelength 600 ~ 700nm) and blue violet light (wavelength 400 ~ 500nm), and only a small amount of green light (500 ~ 600nm).
Red light is the first light quality used in crop cultivation experiment, and it is the necessary light quality for normal crop growth. The amount of biological demand ranks first among all kinds of monochromatic light quality, and the most important light quality in artificial light source. The substances generated under red light make plants grow tall, while the substances generated under blue light promote the accumulation of protein and non carbohydrates and increase plant weight.
The concentration of anthocyanin, carotenoid and chlorophyll decreased by 40%, 11% and 14% respectively, while the fresh weight, dry weight, stem length, leaf length and leaf width increased by 28%, 15%, 14%, 44% and 15% respectively.
Red light regulates light morphogenesis through phytochrome; Red light drives photosynthesis through the absorption of photosynthetic pigments; Red light promotes stem elongation and carbohydrate synthesis, which is conducive to the synthesis of VC and sugar in fruits and vegetables; But inhibit nitrogen assimilation. But red light alone is still a little difficult to cultivate plants well.
Blue Light
Blue light is the necessary supplementary light quality of red light for crop cultivation and normal crop growth. The biological amount of light intensity is second only to red light. Blue light inhibits stem elongation, promotes chlorophyll synthesis, is conducive to nitrogen assimilation and protein synthesis, and is conducive to the synthesis of antioxidant substances. Blue light affects phototropism, photomorphogenesis, stomatal opening and leaf photosynthesis.
LED red light supplemented with LED blue light can improve the dry matter quality, fractional Xue number and seed yield of wheat, and increase the dry matter quality of lettuce. Blue light significantly inhibited the stem growth of lettuce. Increasing blue light in white light can shorten internode, reduce leaf area, reduce relative growth rate and improve N / C efficiency.
Higher plants need blue light for chlorophyll synthesis, chloroplast formation, high chlorophyll a / B ratio and low chloroplast. Excessive blue light is not conducive to plant growth and development. The combination spectrum of red and blue light can promote the growth and development of vegetable seedlings better than red light or blue monochromatic light. The combination ratio of red and blue light required by different plants is different.
Green light
Green light and red and blue light can adjust and adapt to the growth and development of plants harmoniously. Generally, under the red and blue LED compound light, the plants are slightly purple gray, making it difficult to diagnose diseases and disorders, which can be solved by supplementing a small amount of green light. Green light effect is usually opposite to red and blue light effect. For example, green light can reverse the stomatal opening promoted by blue light.
Under strong white light, the photosynthetic quantum yield of the upper chloroplast on the near light surface is lower than that of the lower chloroplast. Because under strong white light, green light can penetrate leaves more than red and blue light, the absorption of additional green light by the lower chloroplast can greatly increase leaf photosynthesis than the absorption of additional red and blue light. Green light may not be considered for low light intensity cultivated plants, green light may not be considered for low density and low canopy thickness facility plants, and green light must be considered for high light intensity, high density and high canopy thickness.
Yellow and orange light
Yellow light, orange light, green light and purple light are important photosynthetic effective radiation, but the demand of plants is small. Adding yellow light on the basis of red and blue light can significantly improve the growth of Spinach Seedlings. Yellow light had the best effect on improving the nutritional quality of leaf lettuce, but blue light was more conducive to significantly improve the content of mineral elements in lettuce; The addition of yellow and purple light could improve the photosynthetic capacity of cherry tomato seedlings and alleviate the weak light stress of red and blue. Compared with white light, purple light and blue light increased the activity of antioxidant enzymes and delayed the aging of plants, while red light, green light and yellow light inhibited the activity of antioxidant enzymes and accelerated the aging process of plants.
Far red light
Although 730nm far red light has little significance for photosynthesis, its intensity and its ratio to 660nm red light play an important role in the morphogenesis of crop plant height and internode length. Plant morphology and height were controlled by light quality regulation and R / FR ratio; When the ratio increases, the plant stem node spacing decreases, the plant dwarfs, and the breeding plants tend to elongate. The change of ratio also has different effects on axillary bud differentiation, chlorophyll content, stomatal index and leaf area. Plants' selective absorption of red light and selective transmission of far red light make plants under shade in a far-infrared enriched light environment.
Ultraviolet (UV)
The wavelength band less than 380nm is called ultraviolet light. According to the physical and biological characteristics of ultraviolet, the wavelength of 320 ~ 380nm is long wave ultraviolet (UV-A), medium wave ultraviolet (UV-B) with wavelength of 280 ~ 320nm and short wave ultraviolet (UV-C) with wavelength of 100 ~ 280nm. 95% of the UV species reaching the ground are UV-A. In the solar spectrum, photosynthetic effective radiation, UV and far red light can regulate plant growth and development.
UV radiation reduces plant leaf area, inhibits hypocotyl elongation, reduces photosynthesis and productivity, and makes plants vulnerable to pathogens, but it can induce flavonoid synthesis and defense mechanism. Under the environment of low UV-B radiation, the plant grows excessively, which also hinders the synthesis of plant pigment, so it is not easy to cover eggplant and fruit vegetables. An important feature of plant factories is the lack of UV-A and UV-B radiation in sunlight. The complete lack of UV radiation will bring negative production effects and affect plant growth and development. Therefore, it is very necessary to regulate the UV radiation level in plant factories, which should be based on production demand and plant tolerance response law.

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