In the visible light, the most absorbed by the green plants is red and orange light (wavelength 600 ~ 700nm) and blue violet (wavelength 400 ~ 500nm), the green light (500 ~ 600nm) only trace absorption.
Red light is the earliest used for crop cultivation test of light quality, is the normal growth of crops must be light quality, the number of biological needs in a variety of monochromatic light quality first, artificial light source of the most important light quality. The material produced under the red light makes the plant grow taller, while the blue light produces the material to promote the accumulation of protein and non-carbohydrate, to plant weight gain.
The contents of fresh weight, dry weight, stem length, leaf length and leaf width of plant were increased by 28%, 15% and 15% respectively, respectively, and the concentration of chlorophyll, carotenoid and chlorophyll decreased by 40%, 11% and 14% respectively. 14%, 44% and 15% respectively.
Red light through photosynthetic pigment to control the formation of light; red light through photosynthetic pigment absorption photosynthesis; red light to promote stem elongation, promote carbohydrate synthesis, is conducive to fruit and vegetable VC and sugar synthesis; but inhibition of nitrogen assimilation. But it is still a bit difficult to cultivate plants with red light alone.
Blu-ray is red for crop cultivation necessary supplemental light quality, is the normal growth of the necessary light quality crops, light biological consumption is second only to red. Blue light inhibits stem elongation, promotes chlorophyll synthesis, facilitates nitrogen assimilation and protein synthesis, and facilitates the synthesis of antioxidant substances. Blue light affects plant light, light morphogenesis, stomatal opening, and leaf photosynthesis.
LED red light to add LED blue light can improve the dry matter quality of wheat, sub-Xue and seed yield, increase the quality of lettuce dry matter. The blue light significantly inhibited the growth of stems of lettuce. Increasing the blue light in the white light can shorten the internode, reduce the leaf area, reduce the relative growth rate and improve the N / C efficiency.
Higher chlorophyll synthesis and chloroplast formation, as well as high chlorophyll a / b ratio and low chloroplast requires blue light. Excess blue light is not conducive to plant growth and development. Red and blue light combination of red light or blue light monochromatic light can promote the growth and development of vegetable seedlings, different plants need red and blue light combination ratio is not the same.
Green light and red and blue light can be adjusted to adapt to the growth and development of plants. Generally in the red and blue LED composite light, the plant slightly purple gray, making the disease and the symptoms are not easy to diagnose, you can add a small amount of green light to solve. Green light effects are usually opposed to red and blue light effects, such as green light can be reversed blue light to promote the opening of the pores and so on.
The photosynthetic quantum yield of the chloroplast above the near - light surface in the upper part of the strong white light was lower than that of the lower chloroplast. Because the green light is stronger than the red light, the blue light can penetrate the leaves, the lower chloroplast absorbs additional green light than the additional absorption of red and blue light can increase the leaf photosynthesis more. Low light intensity cultivated plants do not consider green light, low density low canopy thickness facility plants do not consider green light, high light intensity high density high canopy thickness when green light must be considered.
Yellow and orange light
Yellow, orange, green, and purple are important photosynthetic active radiation, but the plant demand is small. The addition of yellow light on the basis of red and blue light can significantly improve the growth of spinach seedlings. Huangguang has the best effect on improving the nutritive quality of lettuce with leaf, but the blue light is more conducive to significantly increase the mineral content of lettuce.
Adding yellow light and purple light can improve the photosynthetic capacity of cherry tomato seedlings, alleviate the red and blue light stress. Compared with white light, violet and blue light increased the activity of antioxidant enzymes, delayed the aging of plants, while red, green and yellow light inhibited the activity of antioxidant enzymes, accelerated the aging process of plants.
Far red light
Although the far-red light of 730nm is of little significance to photosynthesis, its strength and its ratio to 660nm red light have important effect on crop height and internode length. Moisture regulation, R / FR ratio to control plant morphology and plant height.
When the ratio is larger, the spacing of plants is smaller, the plants are dwarfed and the plants are elongated. The changes of the ratio also have different effects on axillary bud differentiation, chlorophyll content, stomatal index and leaf area. The selective absorption of red light and the selectivity of far red light make the plants located under the shade in a far infrared enrichment environment.
A band with a wavelength less than 380 nm is called ultraviolet light. According to the physical and biological characteristics of ultraviolet light, the wavelength of 320 ~ 380nm for the long-wave ultraviolet (UV-A), wavelength 280 ~ 320nm in the ultraviolet (UV-B) and wavelength of 100 ~ 280nm short-wave ultraviolet (UV-C). 95% of the UV species reaching the ground are UV-A. In the solar spectrum of photosynthetically active radiation, UV and far red light on plant growth and development has a regulatory function.
UV radiation reduces plant leaf area, inhibits hypocotyl elongation, reduces photosynthesis and productivity, makes plants susceptible to pathogen attack, but can induce flavonoid synthesis and defense mechanisms. Low UV-B radiation environment caused by plant leggy, but also hinder the synthesis of plant pigments, not easy to cover eggplant vegetables. An important feature of plant plants is the lack of UV-A and UV-B radiation in the sun, the complete absence of UV radiation can produce negative effects and affect plant growth and development, so it is necessary to regulate the level of UV radiation in plant plants , Need to pay attention to the production needs and plant resistance response based on the law.