Light is a key environmental element for plant growth and agricultural production. Photosynthesis is the main source of inorganic-organic transformation of materials on the earth. The wavelength in the range of 300mm to 800mm can be absorbed by green plant chlorophyll or photoreceptors. Around the world, before the 1970s, because there were only electric light sources emitting continuous spectrum, people’s understanding of the effective light quality of plant photosynthesis and the photosynthetic efficiency of light quality was at a standstill, and there was a lack of research methods to understand the needs of plant spectrum. Whether it is selective or not, it is generally believed that plants can only complete their life history under continuous spectrum artificial light or sunlight.
Among the many studies, the landmark report is about the research results of continuous-spectrum cultivation of higher plants with LED red and blue combined light that can replace fluorescent lamps, etc. These results have laid the foundation for artificial light cultivation with IED red and blue quality as the core. Goins et al. (1997) showed that wheat can complete its life cycle under red LED light source, but the biomass and seed yield are obviously insufficient compared with fluorescent lamps. When supplemented with 10% blue light, the biomass and seed yield of wheat are significantly increased. , The effect is similar to that of a fluorescent lamp. Goins et al. 1998) used Arabidopsis as the test material and obtained similar results. Red and blue combined light can replace continuous spectrum for artificial light plant cultivation. This conclusion has universal application value for horticultural crop cultivation. Therefore, the demand for plant spectrum is selective, discontinuous and alternative, providing biological theoretical support for artificial light cultivation in facility horticulture. The significance is to simplify artificial cultivation from continuous spectrum to red and blue composite light quality, which provides a basis for the research and development of LED light sources and lamps for facility gardening, simplifies lamp design, and reduces manufacturing costs (Liu Wenke and Yang Qichang, 2014).
The use of LED red and blue combined light to replace sunlight and traditional continuous-spectrum light sources for technological breakthroughs in artificial light plant production provides a theoretical basis for the plant cultivation of LED artificial light plants. At present, a consensus has been reached on the light quality requirements and efficiency of plants, that is, the types of necessary light quality for plants are discontinuous and selective. Red light and blue light are necessary for the normal growth and development and life history of plants, and other visible light qualities. Species and far-red light are beneficial light qualities. However, in order to achieve the special goals of plant growth and yield quality, it is sometimes necessary to add some special light quality components to the red and blue combined light base, which can be called beneficial light quality, including other visible light quality besides red and blue, UV and far Red light and so on.
For facility crops, light quality requirements and distribution characteristics have temporal and spatial differences, as well as plant species and varieties. The essential requirement of light quality for plant growth and development is phased. In the germination stage (usually spring), IR and heat are needed; in the vegetative growth stage (summer), more blue light is needed, focusing on the formation of light morphology; in autumn, more is needed. Red light promotes photosynthesis and the accumulation, storage and utilization of carbohydrates.
During photosynthesis of plants, radiant energy is distributed according to wavelength or frequency. In plant physiology, “light quality” is often used to represent the characteristics of the radiation spectrum. Light radiation response (plants) refers to the response of plants to incident radiation, which can be divided into two types: photosynthetic response and light morphological response. Photosynthetic response refers to the response to incident radiation determined by the vegetative growth and productivity of the plant. Photosynthetic response refers to the response to incident radiation determined by the vegetative growth and productivity of the plant. Light morphological response refers to the response of plants and morphology to incident radiation, which is controlled by phytochrome and its light-fixed state, including plant germination, pigment synthesis and morphological development. Photosynthetically active radiation (PAR) refers to the radiant energy in the specific wavelength range that is absorbed by the plant and used for photosynthesis when irradiated on the plant.
Studies have shown that plants can absorb and utilize a variety of light qualities in the continuous spectrum of sunlight, but have a specific spectral response curve. Generally, there are absorption peaks in the red and blue regions, with peaks at 660m and 460mm, respectively. Therefore, red and blue light are of great significance to photosynthesis and photomorphogenesis of plants. The spectral response curve of plants is slightly different due to different plant species, and it is very different from the human eye spectral luminous efficiency curve, and its peak value exists at 555m. Therefore, sunlight is not the best spectrum for plant growth, but sunlight is free and renewable. Modern facility agriculture plant growth supplement light or full artificial light planting plants need to consume a lot of lighting electricity, too much light radiation or light radiation that cannot be used by plants will cause energy waste, thereby reducing the efficiency of the lighting system.
There are two major ways to improve the efficiency of the plant growth supplement light lighting system. First, determine the spectral response curve of plant species and species, the ratio of red and blue demand, and the total amount of light required and the photoperiod; second, provide artificial lighting systems in accordance with the needs of the plant’s light environment. As a nutrient in the process of plant growth, light must not only ensure the healthy growth of plants, but also save lighting energy consumption to the greatest extent and improve the efficiency of the lighting system. In fact, the energy of the light quantum of visible light is inversely proportional to the wavelength. For example, 1mol of 700nm red light quantum energy is 171kJ, and 1mol of 400mm violet light quantum energy is 293kJ, so the visible light energy range is 170~300kJ. It has significantly different physiological effects from light of different light quality (wavelength range), including different effects on the morphology and structure of plants, photosynthesis, and organ growth and development. The dry matter production of plants is the total result of these effects, and the size of plant dry weight is the most important and convincing indicator reflecting the sign of light quality effect.
The light quality requirements of plants-the research and development direction of light parameters of grow lights
Light is a key environmental element for plant growth and agricultural production. Photosynthesis is the main source of inorganic-organic transformation of materials on the earth. The wavelength in the range of 300mm to 800mm can be absorbed by green plant chlorophyll or photoreceptors. Around the world, before the 1970s, because there were only electric light sources emitting continuous spectrum, people’s understanding of the effective light quality of plant photosynthesis and the photosynthetic efficiency of light quality was at a standstill, and there was a lack of research methods to understand the needs of plant spectrum. Whether it is selective or not, it is generally believed that plants can only complete their life history under continuous spectrum artificial light or sunlight.
Since the 1960s, the invention of red LEDs has provided tools for the study of plant light biology. The discovery of blue light in the 1990s promoted the study of light quality biology. Studies have confirmed that the importance of different light qualities in the photosynthetically active radiation spectrum to plant photosynthesis and morphogenesis is not the same. Among them, red light and blue light are the most important to plant photosynthesis, and the relative quantum efficiency of plant photosynthesis is relatively high. This difference in light quality efficiency provides a preliminary scientific basis for determining artificial light cultivation plants with red light and blue light quality as the core.
Among the many studies, the landmark report is about the research results of continuous-spectrum cultivation of higher plants with LED red and blue combined light that can replace fluorescent lamps, etc. These results have laid the foundation for artificial light cultivation with IED red and blue quality as the core. Goins et al. (1997) showed that wheat can complete its life cycle under red LED light source, but the biomass and seed yield are obviously insufficient compared with fluorescent lamps. When supplemented with 10% blue light, the biomass and seed yield of wheat are significantly increased. , The effect is similar to that of a fluorescent lamp. Goins et al. 1998) used Arabidopsis as the test material and obtained similar results. Red and blue combined light can replace continuous spectrum for artificial light plant cultivation. This conclusion has universal application value for horticultural crop cultivation. Therefore, the demand for plant spectrum is selective, discontinuous and alternative, providing biological theoretical support for artificial light cultivation in facility horticulture. The significance is to simplify artificial cultivation from continuous spectrum to red and blue composite light quality, which provides a basis for the research and development of LED light sources and lamps for facility gardening, simplifies lamp design, and reduces manufacturing costs (Liu Wenke and Yang Qichang, 2014).
The use of LED red and blue combined light to replace sunlight and traditional continuous-spectrum light sources for technological breakthroughs in artificial light plant production provides a theoretical basis for the plant cultivation of LED artificial light plants. At present, a consensus has been reached on the light quality requirements and efficiency of plants, that is, the types of necessary light quality for plants are discontinuous and selective. Red light and blue light are necessary for the normal growth and development and life history of plants, and other visible light qualities. Species and far-red light are beneficial light qualities. However, in order to achieve the special goals of plant growth and yield quality, it is sometimes necessary to add some special light quality components to the red and blue combined light base, which can be called beneficial light quality, including other visible light quality besides red and blue, UV and far Red light and so on.
For facility crops, light quality requirements and distribution characteristics have temporal and spatial differences, as well as plant species and varieties. The essential requirement of light quality for plant growth and development is phased. In the germination stage (usually spring), IR and heat are needed; in the vegetative growth stage (summer), more blue light is needed, focusing on the formation of light morphology; in autumn, more is needed. Red light promotes photosynthesis and the accumulation, storage and utilization of carbohydrates.
During photosynthesis of plants, radiant energy is distributed according to wavelength or frequency. In plant physiology, “light quality” is often used to represent the characteristics of the radiation spectrum. Light radiation response (plants) refers to the response of plants to incident radiation, which can be divided into two types: photosynthetic response and light morphological response. Photosynthetic response refers to the response to incident radiation determined by the vegetative growth and productivity of the plant. Photosynthetic response refers to the response to incident radiation determined by the vegetative growth and productivity of the plant. Light morphological response refers to the response of plants and morphology to incident radiation, which is controlled by phytochrome and its light-fixed state, including plant germination, pigment synthesis and morphological development. Photosynthetically active radiation (PAR) refers to the radiant energy in the specific wavelength range that is absorbed by the plant and used for photosynthesis when irradiated on the plant.
Studies have shown that plants can absorb and utilize a variety of light qualities in the continuous spectrum of sunlight, but have a specific spectral response curve. Generally, there are absorption peaks in the red and blue regions, with peaks at 660m and 460mm, respectively. Therefore, red and blue light are of great significance to photosynthesis and photomorphogenesis of plants. The spectral response curve of plants is slightly different due to different plant species, and it is very different from the human eye spectral luminous efficiency curve, and its peak value exists at 555m. Therefore, sunlight is not the best spectrum for plant growth, but sunlight is free and renewable. Modern facility agriculture plant growth supplement light or full artificial light planting plants need to consume a lot of lighting electricity, too much light radiation or light radiation that cannot be used by plants will cause energy waste, thereby reducing the efficiency of the lighting system.
There are two major ways to improve the efficiency of the plant growth supplement light lighting system. First, determine the spectral response curve of plant species and species, the ratio of red and blue demand, and the total amount of light required and the photoperiod; second, provide artificial lighting systems in accordance with the needs of the plant’s light environment. As a nutrient in the process of plant growth, light must not only ensure the healthy growth of plants, but also save lighting energy consumption to the greatest extent and improve the efficiency of the lighting system. In fact, the energy of the light quantum of visible light is inversely proportional to the wavelength. For example, 1mol of 700nm red light quantum energy is 171kJ, and 1mol of 400mm violet light quantum energy is 293kJ, so the visible light energy range is 170~300kJ. It has significantly different physiological effects from light of different light quality (wavelength range), including different effects on the morphology and structure of plants, photosynthesis, and organ growth and development. The dry matter production of plants is the total result of these effects, and the size of plant dry weight is the most important and convincing indicator reflecting the sign of light quality effect.