The mechanism of how crops respond to changes in light signals in the surrounding environment has always been one of the hotspots of international botany research. The plant shade avoidance response refers to the interaction of various forms of light signal receptors in cells, which causes stem elongation after sensing that the plant is shaded. Dense planting (shading) conditions can induce plant shade avoidance syndrome: stem and petiole height elongation, leaf upturning, reduced leaf area, premature leaf senescence, early flowering, reduced branching, reduced root development, increased susceptibility, Reduced stress resistance, etc., eventually lead to crop yield reduction.
Phytochromes (red and far-red photoreceptors) inhibit the avoidance response, and PIFs (phytochrome-interacting proteins) promote the avoidance response. Changes in the amount and quality of light can elicit plant evasion responses to shade avoidance. The lower R/PR ratio of direct or scattered solar yellow is about 1.15, but the ratio is reduced at dawn and dusk, and the value is 0.7 at dusk on sunny days. The presence of nearby plants is the biggest influencer on the quality of light that plants receive. Since photosynthetic pigments absorb most of the visible light, while green light is reflected or transmitted, and far-red light is also radiation that is rarely absorbed by plants, the light reflected and transmitted by green tissues is deficient in red light and rich in far-red light, R/FR ratio was significantly reduced. Franklin and Whitelam, 2007 found that the ratio of reflected light at 1 cm from the edge of the wheat seedling population was only 0.42, and it was as low as 0.1 within the population. Shade environment leads to plastic changes in the development of shade-tolerant plants, known as shade avoidance syndrome, which is one of the most basic developmental strategies in higher plants. The basic features of vaginal avoidance syndrome are stem and petiole elongation, increased apical dominance, and early flowering. High R/FR ratio suppresses vaginal avoidance syndrome. If the place where the plant grows is in shade conditions, it will have a shade avoidance response. In order to get more light, stem growth is accelerated, leaves are upturned, and flowering is advanced, thus affecting the plant type and yield of crops.
photomorphogenesis of plants
Photomorphogenesis refers to the process in which light acts on plants as an environmental signal to regulate plant growth, differentiation and development, also known as light-controlled development. Light-sensing receptors include phytochromes, cryptochromes, photochromes, and super-pigments. These photoreceptors capture and transduce light signals to trigger changes in plant growth and development. Compared with photosynthetic pigments, photoreceptors are very rare in plant cells, but they are sensitive to changes in the external light environment.
The low-energy reaction during photomorphogenesis requires several orders of magnitude lower energy than the energy at the compensation point of photosynthesis in photoplants. The effect of light signals on plants is controlled by the nature of the signal, namely the wavelength. As early as 1937, Flint found that certain wavelengths of light promote the germination of lettuce seeds, while some wavelengths of light inhibit germination. The most effective light quality to promote seed germination is in the red light region (600-700nm), of which the most effective is 660nm red light; while the light that inhibits seed germination is in the far-red light region (720-740nm), the most effective is 730nm far away. red light. When seeds are irradiated with red light and far-red light alternately, seed germination is promoted or inhibited depending on the wavelength of the last irradiated light, regardless of the number of alternations. Table 1-1 shows the effects of different wavelengths of light on the germination of lettuce seeds (quoted from Li Hesheng, 2002)
Typical state of plant photosynthesis（四）
avoidance reaction
The mechanism of how crops respond to changes in light signals in the surrounding environment has always been one of the hotspots of international botany research. The plant shade avoidance response refers to the interaction of various forms of light signal receptors in cells, which causes stem elongation after sensing that the plant is shaded. Dense planting (shading) conditions can induce plant shade avoidance syndrome: stem and petiole height elongation, leaf upturning, reduced leaf area, premature leaf senescence, early flowering, reduced branching, reduced root development, increased susceptibility, Reduced stress resistance, etc., eventually lead to crop yield reduction.
Phytochromes (red and far-red photoreceptors) inhibit the avoidance response, and PIFs (phytochrome-interacting proteins) promote the avoidance response. Changes in the amount and quality of light can elicit plant evasion responses to shade avoidance. The lower R/PR ratio of direct or scattered solar yellow is about 1.15, but the ratio is reduced at dawn and dusk, and the value is 0.7 at dusk on sunny days. The presence of nearby plants is the biggest influencer on the quality of light that plants receive. Since photosynthetic pigments absorb most of the visible light, while green light is reflected or transmitted, and far-red light is also radiation that is rarely absorbed by plants, the light reflected and transmitted by green tissues is deficient in red light and rich in far-red light, R/FR ratio was significantly reduced. Franklin and Whitelam, 2007 found that the ratio of reflected light at 1 cm from the edge of the wheat seedling population was only 0.42, and it was as low as 0.1 within the population. Shade environment leads to plastic changes in the development of shade-tolerant plants, known as shade avoidance syndrome, which is one of the most basic developmental strategies in higher plants. The basic features of vaginal avoidance syndrome are stem and petiole elongation, increased apical dominance, and early flowering. High R/FR ratio suppresses vaginal avoidance syndrome. If the place where the plant grows is in shade conditions, it will have a shade avoidance response. In order to get more light, stem growth is accelerated, leaves are upturned, and flowering is advanced, thus affecting the plant type and yield of crops.
photomorphogenesis of plants
Photomorphogenesis refers to the process in which light acts on plants as an environmental signal to regulate plant growth, differentiation and development, also known as light-controlled development. Light-sensing receptors include phytochromes, cryptochromes, photochromes, and super-pigments. These photoreceptors capture and transduce light signals to trigger changes in plant growth and development. Compared with photosynthetic pigments, photoreceptors are very rare in plant cells, but they are sensitive to changes in the external light environment.
The low-energy reaction during photomorphogenesis requires several orders of magnitude lower energy than the energy at the compensation point of photosynthesis in photoplants. The effect of light signals on plants is controlled by the nature of the signal, namely the wavelength. As early as 1937, Flint found that certain wavelengths of light promote the germination of lettuce seeds, while some wavelengths of light inhibit germination. The most effective light quality to promote seed germination is in the red light region (600-700nm), of which the most effective is 660nm red light; while the light that inhibits seed germination is in the far-red light region (720-740nm), the most effective is 730nm far away. red light. When seeds are irradiated with red light and far-red light alternately, seed germination is promoted or inhibited depending on the wavelength of the last irradiated light, regardless of the number of alternations. Table 1-1 shows the effects of different wavelengths of light on the germination of lettuce seeds (quoted from Li Hesheng, 2002)