Ultraviolet rays refer to light with a wavelength of less than 400m, accounting for 7% of solar radiation. High-intensity ultraviolet light less than 300mm is harmful to plants, and ultraviolet light less than 280m can kill plants. 320～340nm has little effect on plant cryptochrome. Sunlight is a continuous spectrum with wavelengths ranging from 100nm X-rays to 100m radio waves.
99% of the energy in solar radiation is concentrated in the 280-500nm range. The spectral band with a wavelength greater than 760m is called infrared light, and the earth’s surface heat basically comes from solar infrared light radiant energy. Different spectra in sunlight contribute differently to plant photosynthesis, and only the light in the range of 400-700 m is the photosynthetic active radiation of plants, which participates in the photoreaction process of plant carbohydrate synthesis.
According to the perception ability of human eyes, the solar spectrum is usually divided into visible light and invisible light. The wavelength of visible light is 380-760nm, which is subdivided into red light (625～760), orange light (595～626), and yellow light. Light (575-595), green light (470-575), blue light (435-470) and purple light (380-450). Invisible light includes infrared light and ultraviolet light. Among them, the wavelength band of less than 380nm is called ultraviolet light. According to the physical and biological characteristics of ultraviolet light, it is divided into 3 bands: long-wave ultraviolet (UV-A) with a wavelength of 320～380nm, medium-wave ultraviolet (UV-B) with a wavelength of 280～320m and a wavelength of 100～280mm Short-wave ultraviolet (UV-C).
In the total solar radiation, visible light accounts for about 50%, infrared light accounts for 48% to 49%, and the rest ultraviolet light accounts for 1% to 2%. Studies have shown that photosynthetically active radiation, UV and far-red light in the sunlight spectrum have regulatory functions on plant growth and development, and have application value and regulatory necessity in agricultural production.
The UV and photosynthetically active radiation in the plastic greenhouse is greatly reduced due to the shielding effect of the greenhouse film, while the intensity of UV and photosynthetically active radiation in the glass greenhouse is reduced by as much as 66% and 45%, and the maximum loss rate occurs at 12:00, and the loss rate It increases with the increase in the intensity of sunlight. Therefore, under facility conditions, the light intensity obtained by plants increases with the increase of sunlight intensity, and the inflection point is 12:00.
Ultraviolet radiation reduces plant leaf area, inhibits hypocotyl elongation, reduces photosynthesis and productivity, and makes plants vulnerable to pathogens. However, it can induce xanthoid synthesis and defense mechanisms and promote anthocyanidin synthesis. UV-B exposure resulted in dwarf plant phenotypes, small thick leaves, short petioles, increased axillary branches and root-to-shoot ratio.
Research on 16 rice cultivars from 7 countries grown in the greenhouse shows that 4 cultivars have increased the total biomass quantity caused by the addition of UV-B; 12 cultivars have decreased; those cultivars that are sensitive to UVB The leaf area and fraction were significantly reduced; 6 cultivars had increased chlorophyll content (2 of them reached a significant level); 5 cultivars had significantly reduced leaf photosynthetic rate, and 1 cultivated species had significantly increased chlorophyll content ( Its total biomass has also increased significantly) (Teramura et al., 1991).
The ratio of UV-B/PAR is an important determinant of the response of plants to UV-B. For example, UVB and PAR together affect the morphology and oil yield of peppermint, and the production of high-quality oil requires a high level of unfiltered natural light (Behn et al., 2010).
The blade absorbs 90% of incident UV-B. The leaves contain water-soluble phenolic pigment flavonoids, which strongly absorb UV-B but not PAR. Therefore, in many kinds of plant leaves, there is very little UV-B that can be transmitted to the place where the photosynthetic apparatus can be destroyed. The net photosynthetic rate of pea grown in the greenhouse was significantly reduced after exposure to UV-B (280-315nm) for 4 to 5 hours, while the mesophyll resistance and dark respiration of the leaves to the diffusion of CO2 were significantly increased. The dry weight of the plant was 9d after UV-B exposure Significantly lower than control plants (Brandle et al., 1977). UV-B can reduce the concentration of ascorbic acid and B-carotene, but can effectively promote anthocyanin synthesis. UV-B exposure resulted in dwarf plant phenotypes, small and thick leaves with short petioles, increased axillary branches, and changes in root-to-shoot ratio. UV-B adaptation also affects the relationship between plants and herbivores. Therefore, UV-B is a regulatory factor that controls plants and their relationship with biotic and abiotic environments.
The ratio of UV-B/PAR is an important determinant of the response of plants to UV-B. For example, UV-B and PAR affect the morphology and oil yield of peppermint (Mentha x piperita). Therefore, the production of high-quality oil requires a high level of unfiltered natural light (Behn et al., 2010). Under field conditions, supplemental ultraviolet radiation (UV-B, 300m, 3.0 or 5.1kJ/m2) reduced the yield of soybean cultivar Essex by 20%, but there was no significant change in seed protein and lipid content (Teramura et al., 1990). The investigation results of 16 rice cultivation from 7 different regions in China, India, Philippines, Nepal, Thailand, Vietnam and Sri Lanka that were grown in the greenhouse showed that the addition of UV-B led to an increase in total biomass quality in 4 (of which, Only 1 cultivar from Sri Lanka reached a significant level, and 12 cultivars decreased (6 of which reached a significant level); the leaf area and fraction of cultivars that are sensitive to UV-B were significantly reduced; chlorophyll content There are 6 cultivars that have increased (including 2 that reach a significant level); 5 cultivars have significantly reduced leaf photosynthetic rate, and 1 cultivar has significantly increased (its total biological quality has also increased significantly) ( Teramura et al., 1991).
Although laboratory studies on the effects of UV-B are effective in confirming transcription factors and other molecular and physiological factors, due to the use of higher UV-B levels, there is no accompanying UV-A and often very low levels. Background PAR, laboratory research results usually cannot be mechanically extrapolated to the actual natural environment. Field studies usually use UV lamps to increase or use filters to reduce UV-B levels.
Ultraviolet (UV) Plant Photobiology
Ultraviolet rays refer to light with a wavelength of less than 400m, accounting for 7% of solar radiation. High-intensity ultraviolet light less than 300mm is harmful to plants, and ultraviolet light less than 280m can kill plants. 320～340nm has little effect on plant cryptochrome. Sunlight is a continuous spectrum with wavelengths ranging from 100nm X-rays to 100m radio waves.
99% of the energy in solar radiation is concentrated in the 280-500nm range. The spectral band with a wavelength greater than 760m is called infrared light, and the earth’s surface heat basically comes from solar infrared light radiant energy. Different spectra in sunlight contribute differently to plant photosynthesis, and only the light in the range of 400-700 m is the photosynthetic active radiation of plants, which participates in the photoreaction process of plant carbohydrate synthesis.
According to the perception ability of human eyes, the solar spectrum is usually divided into visible light and invisible light. The wavelength of visible light is 380-760nm, which is subdivided into red light (625～760), orange light (595～626), and yellow light. Light (575-595), green light (470-575), blue light (435-470) and purple light (380-450). Invisible light includes infrared light and ultraviolet light. Among them, the wavelength band of less than 380nm is called ultraviolet light. According to the physical and biological characteristics of ultraviolet light, it is divided into 3 bands: long-wave ultraviolet (UV-A) with a wavelength of 320～380nm, medium-wave ultraviolet (UV-B) with a wavelength of 280～320m and a wavelength of 100～280mm Short-wave ultraviolet (UV-C).
In the total solar radiation, visible light accounts for about 50%, infrared light accounts for 48% to 49%, and the rest ultraviolet light accounts for 1% to 2%. Studies have shown that photosynthetically active radiation, UV and far-red light in the sunlight spectrum have regulatory functions on plant growth and development, and have application value and regulatory necessity in agricultural production.
The UV and photosynthetically active radiation in the plastic greenhouse is greatly reduced due to the shielding effect of the greenhouse film, while the intensity of UV and photosynthetically active radiation in the glass greenhouse is reduced by as much as 66% and 45%, and the maximum loss rate occurs at 12:00, and the loss rate It increases with the increase in the intensity of sunlight. Therefore, under facility conditions, the light intensity obtained by plants increases with the increase of sunlight intensity, and the inflection point is 12:00.
Ultraviolet radiation reduces plant leaf area, inhibits hypocotyl elongation, reduces photosynthesis and productivity, and makes plants vulnerable to pathogens. However, it can induce xanthoid synthesis and defense mechanisms and promote anthocyanidin synthesis. UV-B exposure resulted in dwarf plant phenotypes, small thick leaves, short petioles, increased axillary branches and root-to-shoot ratio.
Research on 16 rice cultivars from 7 countries grown in the greenhouse shows that 4 cultivars have increased the total biomass quantity caused by the addition of UV-B; 12 cultivars have decreased; those cultivars that are sensitive to UVB The leaf area and fraction were significantly reduced; 6 cultivars had increased chlorophyll content (2 of them reached a significant level); 5 cultivars had significantly reduced leaf photosynthetic rate, and 1 cultivated species had significantly increased chlorophyll content ( Its total biomass has also increased significantly) (Teramura et al., 1991).
The ratio of UV-B/PAR is an important determinant of the response of plants to UV-B. For example, UVB and PAR together affect the morphology and oil yield of peppermint, and the production of high-quality oil requires a high level of unfiltered natural light (Behn et al., 2010).
The blade absorbs 90% of incident UV-B. The leaves contain water-soluble phenolic pigment flavonoids, which strongly absorb UV-B but not PAR. Therefore, in many kinds of plant leaves, there is very little UV-B that can be transmitted to the place where the photosynthetic apparatus can be destroyed. The net photosynthetic rate of pea grown in the greenhouse was significantly reduced after exposure to UV-B (280-315nm) for 4 to 5 hours, while the mesophyll resistance and dark respiration of the leaves to the diffusion of CO2 were significantly increased. The dry weight of the plant was 9d after UV-B exposure Significantly lower than control plants (Brandle et al., 1977). UV-B can reduce the concentration of ascorbic acid and B-carotene, but can effectively promote anthocyanin synthesis. UV-B exposure resulted in dwarf plant phenotypes, small and thick leaves with short petioles, increased axillary branches, and changes in root-to-shoot ratio. UV-B adaptation also affects the relationship between plants and herbivores. Therefore, UV-B is a regulatory factor that controls plants and their relationship with biotic and abiotic environments.
The ratio of UV-B/PAR is an important determinant of the response of plants to UV-B. For example, UV-B and PAR affect the morphology and oil yield of peppermint (Mentha x piperita). Therefore, the production of high-quality oil requires a high level of unfiltered natural light (Behn et al., 2010). Under field conditions, supplemental ultraviolet radiation (UV-B, 300m, 3.0 or 5.1kJ/m2) reduced the yield of soybean cultivar Essex by 20%, but there was no significant change in seed protein and lipid content (Teramura et al., 1990). The investigation results of 16 rice cultivation from 7 different regions in China, India, Philippines, Nepal, Thailand, Vietnam and Sri Lanka that were grown in the greenhouse showed that the addition of UV-B led to an increase in total biomass quality in 4 (of which, Only 1 cultivar from Sri Lanka reached a significant level, and 12 cultivars decreased (6 of which reached a significant level); the leaf area and fraction of cultivars that are sensitive to UV-B were significantly reduced; chlorophyll content There are 6 cultivars that have increased (including 2 that reach a significant level); 5 cultivars have significantly reduced leaf photosynthetic rate, and 1 cultivar has significantly increased (its total biological quality has also increased significantly) ( Teramura et al., 1991).
Although laboratory studies on the effects of UV-B are effective in confirming transcription factors and other molecular and physiological factors, due to the use of higher UV-B levels, there is no accompanying UV-A and often very low levels. Background PAR, laboratory research results usually cannot be mechanically extrapolated to the actual natural environment. Field studies usually use UV lamps to increase or use filters to reduce UV-B levels.
UV has application value in facility horticulture, and UV-LED has begun to be applied in practice. It has value in regulating the color of plants and regulating the synthesis and accumulation of secondary metabolites. However, the application of UV in facility gardening should follow the principle of short-term, small amount, and multiple times to avoid plant damage.