In the solar spectrum, the optical radiation in the 300-800mm band is called Physio-logically active radiation, and the 400-700mm optical radiation is called the Plant Photosynthetically Active Radiation (PAR). The former includes near-ultraviolet and far-red light, while infrared radiation is not physiologically effective radiation. 380～780nm is visible light, part of ultraviolet light and far-red light are not visible light.
The part of non-photosynthetically active radiation in physiologically effective radiation is near ultraviolet radiation (Near ultraviolet radiation, wavelength 280~400mm) and far-red radiation (wavelength 700~800mm), which directly affect the photomorphogenesis and formation of plants. Production of secondary metabolites. Near infrared and infrared radiation with a wavelength above 800mm have no effect on the physiological processes of photosynthesis of plants, but after being absorbed by plants, they will be converted into heat energy, which has a heating effect on plants. Photosynthetic active radiation accounts for the earth’s oceans. The proportion of solar radiation on the plane is 45% to 50%.
In facility horticulture lighting, the light intensity is represented by the number of light quanta (mol). The photochemical reaction of plants does not depend on the energy of light quanta, but depends on the number of light quanta. Therefore, although the energy of red light is less than that of blue light, its relative photosynthetic efficiency is high. In facility gardening, photosynthetically effective light quantum flux (PPF) and photosynthetically effective light quantum flux density (PPFD) are commonly used as units to measure light intensity.
In visual lighting, the commonly used luminous flux represents the integral of the product of the light energy of each wavelength in the visible light range and the light visual efficiency, in units of lumens (lm). The ratio of luminous flux to power consumption is an index to evaluate the luminous efficiency of lamps (lm/W). Illuminance is the quotient of the luminous flux divided by the illuminated area, and the unit is lx.
In fact, the illuminance of 1lm of light on an area of 1m2 is 1k. The conversion factor for converting the unit of illuminance into PPF depends on factors such as the type of light source (spectral distribution), and the type of wavelength. Long-term studies have shown that the light energy absorbed by plant photosynthesis in the visible light spectrum (380~760nm) accounts for 60%~65% of its physiological radiation light energy. , Orange light (accounting for about 55% of physiological radiation) and blue and violet light (accounting for about 8% of physiological radiation) with a wavelength of 400~510nm (wavelength peak is 450m) are the absorption peak areas.
Therefore, the development of plant artificial light sources with these two wavebands (especially wave crests) as the main body will greatly improve its light energy utilization efficiency. In recent years, with the continuous progress of LED technology, it is possible to achieve this goal. LEDs can emit monochromatic light (such as blue light with a peak of 450 nm, red light with a peak of 660 nm, etc.) that are required for plant growth, and the spectral domain width is only ±20m, and the combination of red and blue LEDs can also form photosynthesis with plants The function and morphology are basically consistent with the spectrum, the light energy utilization efficiency reaches 80% to 90%, and the energy saving effect is extremely significant.
Plant light quality biology-the basis of LED plant lighting theory
In the solar spectrum, the optical radiation in the 300-800mm band is called Physio-logically active radiation, and the 400-700mm optical radiation is called the Plant Photosynthetically Active Radiation (PAR). The former includes near-ultraviolet and far-red light, while infrared radiation is not physiologically effective radiation. 380～780nm is visible light, part of ultraviolet light and far-red light are not visible light.
The part of non-photosynthetically active radiation in physiologically effective radiation is near ultraviolet radiation (Near ultraviolet radiation, wavelength 280~400mm) and far-red radiation (wavelength 700~800mm), which directly affect the photomorphogenesis and formation of plants. Production of secondary metabolites. Near infrared and infrared radiation with a wavelength above 800mm have no effect on the physiological processes of photosynthesis of plants, but after being absorbed by plants, they will be converted into heat energy, which has a heating effect on plants. Photosynthetic active radiation accounts for the earth’s oceans. The proportion of solar radiation on the plane is 45% to 50%.
In facility horticulture lighting, the light intensity is represented by the number of light quanta (mol). The photochemical reaction of plants does not depend on the energy of light quanta, but depends on the number of light quanta. Therefore, although the energy of red light is less than that of blue light, its relative photosynthetic efficiency is high. In facility gardening, photosynthetically effective light quantum flux (PPF) and photosynthetically effective light quantum flux density (PPFD) are commonly used as units to measure light intensity.
In visual lighting, the commonly used luminous flux represents the integral of the product of the light energy of each wavelength in the visible light range and the light visual efficiency, in units of lumens (lm). The ratio of luminous flux to power consumption is an index to evaluate the luminous efficiency of lamps (lm/W). Illuminance is the quotient of the luminous flux divided by the illuminated area, and the unit is lx.
In fact, the illuminance of 1lm of light on an area of 1m2 is 1k. The conversion factor for converting the unit of illuminance into PPF depends on factors such as the type of light source (spectral distribution), and the type of wavelength. Long-term studies have shown that the light energy absorbed by plant photosynthesis in the visible light spectrum (380~760nm) accounts for 60%~65% of its physiological radiation light energy. , Orange light (accounting for about 55% of physiological radiation) and blue and violet light (accounting for about 8% of physiological radiation) with a wavelength of 400~510nm (wavelength peak is 450m) are the absorption peak areas.
Therefore, the development of plant artificial light sources with these two wavebands (especially wave crests) as the main body will greatly improve its light energy utilization efficiency. In recent years, with the continuous progress of LED technology, it is possible to achieve this goal. LEDs can emit monochromatic light (such as blue light with a peak of 450 nm, red light with a peak of 660 nm, etc.) that are required for plant growth, and the spectral domain width is only ±20m, and the combination of red and blue LEDs can also form photosynthesis with plants The function and morphology are basically consistent with the spectrum, the light energy utilization efficiency reaches 80% to 90%, and the energy saving effect is extremely significant.