1. LED plant growth lights emit 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 green light (500-600nm) is only slightly absorbed.
Red light is the light quality that was first used in crop cultivation experiments. It is a 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 in artificial light sources.
The substances generated under the red light make the plants grow taller, while the substances generated under the blue light of the LED plant growth lamp promote the accumulation of protein and non-carbohydrates and increase the weight of the plants.
Red light regulates photomorphogenesis through phytochrome; red light drives photosynthesis through photosynthetic pigment absorption; red light promotes stem elongation, promotes carbohydrate synthesis, and is beneficial to the synthesis of VC and sugar in fruits and vegetables; but inhibits nitrogen assimilation.
2. LED plant growth lights emit blue light
Blue light is the necessary supplementary light quality for red light to be used in crop cultivation, and it is necessary for the normal growth of crops. The light intensity biological consumption is second only to red light.
Blue light inhibits stem elongation, promotes chlorophyll synthesis, is beneficial to nitrogen assimilation and protein synthesis, and is beneficial to the synthesis of antioxidant substances. Blue light affects plant phototropism, photomorphogenesis, stomatal opening, and leaf photosynthesis.
The LED red light complements the blue light of the LED plant growth lamp, which can improve the dry matter quantity, separation number and seed yield of wheat, and increase the dry matter quantity of lettuce. Blue light significantly inhibited the growth of leaf lettuce stems.
Adding blue light to white light can shorten internodes, reduce leaf area, reduce relative growth rate and improve N/C efficiency. Higher plants need blue light for chlorophyll synthesis and chloroplast formation, as well as those with high chlorophyll a/b ratio and low chloroplast.
The combined spectrum of red and blue light can promote the growth and development of vegetable seedlings more than red light or blue light monochromatic light, and the combination ratio of red and blue light required by different plants is different.
3. LED plant growth lights emit green light
Green light and red and blue light can harmoniously adjust and adapt to the growth and development of plants. Generally, under the composite light of red and blue LEDs, 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 is not considered for low-intensity cultivated plants, and green light for plant growth lights is not considered for low-density and low-canopy-thickness facility plants. Green light must be considered for high-intensity, high-density, and high-canopy thickness.
4. LED plant growth lights emit yellow and orange light
Yellow light, orange light, green light, and purple light are all important photosynthetically active radiation, but the plant needs less. Adding yellow light to 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. Adding yellow light and purple light of LED plant growth lights can improve the photosynthetic capacity of cherry tomato seedlings and alleviate the stress of red and blue weak light.
5. LED plant growth lamp emits far red light
Although the 730nm far-red light is of little significance to photosynthesis, its intensity and its ratio to 660nm red light play an important role in the establishment of plant height, internode length and other morphology of crops.
The selective absorption of red light and the selective transmission of far-red light by plants make the plants under the shade in a far-infrared-rich light environment.
6. LED plant growth lamp emits ultraviolet light (UV)
The band with a wavelength less than 380nm is called ultraviolet light, and 95% of the UV species that reach the ground are UV-A. In the solar spectrum, photosynthetic active radiation, UV and far-red light have the function of regulating plant growth and development.
Ultraviolet radiation reduces plant leaf area, inhibits hypocotyl elongation, reduces photosynthesis and productivity, and makes plants vulnerable to pathogens, but can induce flavonoid synthesis and defense mechanisms.
The complete lack of UV radiation will bring negative effects on production and affect plant growth and development. Therefore, it is very necessary to regulate the UV radiation level of plant growth lamps in plant factories. It is necessary to pay attention to production requirements and plant tolerance response rules.