The evaluation of the effect of light quality on plant photosynthesis is widely derived from the light quantum yield (YPF) curve, which shows that the photosynthesis of 600~660 mm red orange light is 20%~30% higher than that of 400~460 nm blue green and blue light. When analyzing light quality based on YPF curve, HPS has the same or higher effect as better LED lamps, because it has high light quantum output near 600nm, and low output in blue, blue-green and green light regions.
This quantum yield spectrum curve is formed on the basis of short-term measurement data under the condition of single leaf and low light intensity (Nelson and Bugbee, 2014). However, the YPF curve was drawn by short-term measurement of a single leaf under low light conditions. Chlorophyll and pigment of green leaves have weak ability to absorb green light (Terashima et al., 2009), but Terashima et al. (2009) pointed out that the photosynthesis efficiency of sunflower leaves driven by green light mixed with strong white light is higher than red light. Therefore, green light is often considered to be ineffective for plant growth, but it may be effective for plant growth under strong light conditions. High intensity green LED can effectively improve plant growth, especially short wavelength green light is more effective for plant growth (Johkan et al., 2012).
full spectrum
In the past 30 years, many long-term studies on the whole plant under high light intensity conditions have shown that the effect of light quality on plant growth rate is far less than light intensity (Cope et al., 2014; Johkan et al., 2012). Light quality, especially blue light, can change the cell expansion rate and leaf expansion rate of several plants (Dougher and Bug bee, 2004), plant height and plant morphology (Cope and Bugbee, 2013; Dougher and Bug bee, 2001; Yorio et al., 2001). But the direct effect of blue light on photosynthesis is very small. The effect of light quality on the dry and fresh weight of the whole plant generally occurs in the absence or low natural light, which is caused by the changes in leaf expansion and radiation capture at the early growth stage (Cope et al., 2014).
Based on the quantum moles of photosynthetic light per joule, the light colors with the highest electrical efficiency of LED light are blue light, red light and cold white light, so LED lamps generally combine to generate these colors. LED light quality of other colors can be used to improve the light quality of specific wavelengths, and some aspects of plant growth can be controlled with the help of monochromatic light properties (Ya2012; Morrow and Tibbitts, 2008). The lack of UV radiation in LED lamps significantly reduces lamp efficiency due to UV-LED. The sunlight contains 9% UV of PPF, and the standard electric light source contains 0.3%~8% UV radiation. The lack of UV causes some plant maladjustment symptoms under sunlight conditions (intunmercence, Morrow and Tibbitts, 1988). LED lamps are used for photosynthetic light supplement. The lack of far red light radiation (710~740nm) shortens the flowering time of several photoperiodic plants (GraigRungle, 2013). Green light (530-580nm) is absent or absent in LED lamps, which can penetrate the canopy and more effectively transmit to the lower leaves (Kim et al., 2004). That is to say, the wavelength of each incident light quantum is equal to that of a single leaf under low light intensity (150 μ Mol/m2) has an impact on photosynthesis.
Analysis on the Advantages of Semiconductor Light Compensation in Greenhouse（三）
The evaluation of the effect of light quality on plant photosynthesis is widely derived from the light quantum yield (YPF) curve, which shows that the photosynthesis of 600~660 mm red orange light is 20%~30% higher than that of 400~460 nm blue green and blue light. When analyzing light quality based on YPF curve, HPS has the same or higher effect as better LED lamps, because it has high light quantum output near 600nm, and low output in blue, blue-green and green light regions.
This quantum yield spectrum curve is formed on the basis of short-term measurement data under the condition of single leaf and low light intensity (Nelson and Bugbee, 2014). However, the YPF curve was drawn by short-term measurement of a single leaf under low light conditions. Chlorophyll and pigment of green leaves have weak ability to absorb green light (Terashima et al., 2009), but Terashima et al. (2009) pointed out that the photosynthesis efficiency of sunflower leaves driven by green light mixed with strong white light is higher than red light. Therefore, green light is often considered to be ineffective for plant growth, but it may be effective for plant growth under strong light conditions. High intensity green LED can effectively improve plant growth, especially short wavelength green light is more effective for plant growth (Johkan et al., 2012).
In the past 30 years, many long-term studies on the whole plant under high light intensity conditions have shown that the effect of light quality on plant growth rate is far less than light intensity (Cope et al., 2014; Johkan et al., 2012). Light quality, especially blue light, can change the cell expansion rate and leaf expansion rate of several plants (Dougher and Bug bee, 2004), plant height and plant morphology (Cope and Bugbee, 2013; Dougher and Bug bee, 2001; Yorio et al., 2001). But the direct effect of blue light on photosynthesis is very small. The effect of light quality on the dry and fresh weight of the whole plant generally occurs in the absence or low natural light, which is caused by the changes in leaf expansion and radiation capture at the early growth stage (Cope et al., 2014).
Based on the quantum moles of photosynthetic light per joule, the light colors with the highest electrical efficiency of LED light are blue light, red light and cold white light, so LED lamps generally combine to generate these colors. LED light quality of other colors can be used to improve the light quality of specific wavelengths, and some aspects of plant growth can be controlled with the help of monochromatic light properties (Ya2012; Morrow and Tibbitts, 2008). The lack of UV radiation in LED lamps significantly reduces lamp efficiency due to UV-LED. The sunlight contains 9% UV of PPF, and the standard electric light source contains 0.3%~8% UV radiation. The lack of UV causes some plant maladjustment symptoms under sunlight conditions (intunmercence, Morrow and Tibbitts, 1988). LED lamps are used for photosynthetic light supplement. The lack of far red light radiation (710~740nm) shortens the flowering time of several photoperiodic plants (GraigRungle, 2013). Green light (530-580nm) is absent or absent in LED lamps, which can penetrate the canopy and more effectively transmit to the lower leaves (Kim et al., 2004). That is to say, the wavelength of each incident light quantum is equal to that of a single leaf under low light intensity (150 μ Mol/m2) has an impact on photosynthesis.