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What is a full spectrum LED grow light?

Break down of the effects of LED’s main spectral wavelength on plants

The full spectrum LED grow light  is a LED lighting source developed by simulating the solar spectrum that is conducive to plant growth. The visible light in the spectrum has a reasonable distribution ratio from the blue part of 380NM to the red part of 780NM, and the light wave curve imitates the shape of the sun’s spectrum. The light color is like about 10 o’clock in the morning. Bright daylight color, strong color rendering, small color temperature drift, high luminous efficiency and large luminous flux.

But for all those full spectrum LED grow lights on the market, actually different manufacturers make their own full spectrum with different ratio of each color within the spectrum. So in order to choose the most suitable full spectrum LED grow light  for your plants, it is better to understand how each color within the full spectrum affect the plant growth. And combining with your growing purpose, then it is more easy to choose the right full spectrum LED grow lights for your specific growing.

Red light

Among visible light, red-orange light (wavelength 600-700nm) and blue-violet light (wavelength 400-500nm) are most absorbed by green plants, and only a small amount of green light (500-600nm) is absorbed.

Red light is the first light quality used in crop cultivation experiments. It is necessary light quality for the normal growth of crops. The number of biological requirements ranks first among all kinds of monochromatic light quality, and the most important light quality among artificial light sources. Substances produced under red light make plants grow taller, while substances produced under blue light promote the accumulation of protein and non-carbohydrates and increase plant weight.

The far-infrared supplementation reduces the concentration of anthocyanin, carotenoid and chlorophyll by 40%, 11% and 14% respectively, and increases the fresh weight, dry weight, stem length, leaf length and leaf width of the plant by 28%, 15%, respectively. 14%, 44% and 15%.

Red light regulates photomorphogenesis through photosensitizing pigments; red light drives photosynthesis through the absorption of photosynthetic pigments; red light promotes stem elongation and promotes carbohydrate synthesis, which is beneficial to the synthesis of VC and sugars in fruits and vegetables; but inhibits nitrogen assimilation. But it is still a bit difficult for Hongguang alone to cultivate plants well.

Blue light

Blue light is the necessary supplementary light quality for red light for crop cultivation, and it is necessary light quality for normal crop growth. The amount of light intensity is second only to red light. Blue light inhibits stem elongation, promotes chlorophyll synthesis, facilitates nitrogen assimilation and protein synthesis, and facilitates the synthesis of antioxidant substances. Blue light affects the phototropism, photomorphogenesis, stomata opening, and leaf photosynthesis of plants.

The LED red light supplementing the LED blue light can improve the dry matter quality, fraction and seed yield of wheat, and increase the dry matter quality of lettuce. Blue light significantly inhibited the growth of loose leaf lettuce stems. Increasing blue light in white light can shorten internodes, reduce leaf area, reduce relative growth rate and increase N/C efficiency.

Higher plants require blue light for chlorophyll synthesis and chloroplast formation, as well as high chlorophyll a/b ratio and low chloroplast. Excessive blue light is not conducive to plant growth and development. The combination of red and blue light can promote the growth and development of vegetable seedlings more than red or blue monochromatic light. Different plants require different combinations of red and blue light.

Green light

Green light and red and blue light can harmoniously adjust and adapt to the growth and development of plants. Generally, under the combined light of red and blue LEDs, plants are slightly purple-gray, making it difficult to diagnose diseases and disorders, and can be solved by supplementing a small amount of green light. The green light effect is usually opposed to the red and blue light effects. For example, green light can reverse the stoma opening promoted by blue light.

Under strong white light, the photosynthetic quantum yield of the upper chloroplast on the low-light surface is lower than that of the lower chloroplast. Because green light can penetrate leaves better than red and blue light under strong white light, the lower chloroplast absorbing additional green light can increase leaf photosynthesis to a greater extent than absorbing additional red and blue light. Green light is not considered for cultivated plants with low light intensity, green light is not considered for plants with low density and low canopy thickness, green light must be considered for high light intensity, high density and high canopy thickness.

Yellow light and orange light

Yellow light, orange light, green light, and violet light are all important photosynthetically active radiation, but the demand for plants is small. Adding yellow light on the basis of red and blue light can significantly improve the growth of spinach seedlings. Yellow light has the best effect on improving the nutritional quality of leaf lettuce, but blue light is more conducive to significantly increase the content of mineral elements in lettuce; adding yellow light and violet light can improve the photosynthetic capacity of cherry tomato seedlings and alleviate red and blue weak light stress. Compared with white light, purple light and blue light increase the activity of antioxidant enzymes and delay the senescence of plants, while red light, green light and yellow light inhibit the activity of antioxidant enzymes and accelerate the senescence process of plants.

Far red light

Although the far-red light of 730nm is of little significance to photosynthesis, its intensity and its ratio to the red light of 660nm play an important role in the morphology of crops such as plant height and internode length. By adjusting the light quality, the R/FR ratio controls the plant morphology and plant height; when the ratio becomes larger, the distance between the plant stem nodes becomes smaller, the plant is dwarfed, and the propagation plant tends to elongate. The change of the ratio also affects the axillary bud differentiation and chlorophyll content , Stomatal index and leaf area have different degrees of influence. The selective absorption of red light by plants and the selective transmission of far-red light make plants under shading in a light environment enriched in far-infrared.

Ultraviolet light (UV)

The band with a wavelength less than 380nm is called ultraviolet light. According to the physical and biological characteristics of ultraviolet rays, the wavelengths of 320-380nm are long-wave ultraviolet (UV-A), medium-wave ultraviolet (UV-B) with wavelengths of 280-320nm and short-wave ultraviolet (UV-C) with wavelengths of 100-280nm. 95% of the UV species that reach the ground are UV-A. In the sunlight spectrum, photosynthetically active radiation, UV and far-red light have regulatory functions on plant growth and development.

Ultraviolet radiation reduces plant leaf area, inhibits hypocotyl elongation, reduces photosynthesis and productivity, makes plants vulnerable to pathogens, but can induce flavonoid synthesis and defense mechanisms. Under the environment of low UV-B radiation, the plants will grow elongated and will hinder the synthesis of plant pigments, making it difficult to cover solanaceous vegetables. An important feature of plant factories is the lack of UV-A and UV-B radiation in sunlight. Complete lack of UV radiation will bring about negative production effects and affect plant growth and development. Therefore, it is necessary to regulate the level of UV radiation in plant factories. , Need to pay attention to the production demand and plant tolerance response law as the basis.

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