1 - what is the meaning of light to plants?
Light is one of the most important environmental factors for plant growth and development. The wavelength of 43% ~ 52.5% of sunlight reaching the ground is 400 ~ 700nm, which is the visible light that can be seen by human eyes. This is the photosynthetic energy and environmental signal, which affects the growth, development, yield and quality of plants through photosynthesis and light morphogenesis.
First, photosynthesis is the basis for the formation of plant biomass and yield. 95% of plant dry matter comes from carbohydrates produced by photosynthesis. Plants have complex responses to light conditions, including light response, light inhibition, light adaptation, shade avoidance and so on. In the panchromatic spectrum of the sun, only some wavelengths of light are absorbed by plants to produce photosynthesis. Plant leaf morphology, plant physiological response, etc. will affect photosynthesis.
Second, light morphogenesis refers to the process in which light acts on plants as an environmental signal to regulate plant growth, differentiation and development. The content of light receptors in plant cells is small, but they are very sensitive to the changes of external light environment. For example, 600 ~ 700nm red light field promotes lettuce seed germination, while 720 ~ 740nm far red light field inhibits lettuce seed germination.
2. What does "light and fertilizer" mean?
Plants use different wavelengths for photosynthesis, that is, plants are selective to the spectrum. The light energy absorbed by plants in the visible spectrum (380 ~ 760nm) is about 60%, in which the red orange light with the wavelength of 610 ~ 720nm (the peak is 660nm) and the blue violet light with the wavelength of 400 ~ 510nm (the peak is 450nm) are the absorption peak areas. These two bands become the "light fertilizer" of plants 。
LED can emit monochromatic light required for plant growth. The combination of monochromatic light can form the spectrum required for plant photosynthesis and morphogenesis. Led plant growth light source can improve the light energy utilization of plants.
3 - what is the photosynthetic mechanism and what is its influence?
In a broad sense, light and mechanism is the mechanism that can carry out some or all reactions of photosynthesis, ranging from chloroplasts and thylakoids to mesophyll cells, leaf organs, and even the whole plant. In a narrow sense, it is chloroplast.
First, photosynthetic mechanism is affected by light stress. Too strong and too weak light will lead to plant light stress, inhibit photosynthesis and reduce photosynthetic efficiency. Under strong light, plants produce reactive oxygen species and photoinhibition.
Second, the photosynthetic mechanism is affected by temperature. The periodic change of temperature affects the fixation and reduction of photosynthetic carbon, sucrose synthesis, transportation and distribution of photosynthetic products and electron transfer.
Third, photosynthetic mechanism is affected by nutrient supply. Nitrogen nutrition is the basis of plant life. The average correlation coefficient between leaf photosynthetic capacity and nitrogen content was 0.9. The photosynthetic rate of light saturation increased linearly with the increase of leaf nitrogen content. Therefore, maintaining the supply of nitrogen nutrition and other elements related to chlorophyll synthesis and metabolism is very important to ensure the activity of photosynthetic mechanism.
Fourth, photosynthetic mechanism is affected by carbon dioxide. Carbon dioxide is the main raw material of photosynthesis. The increase of carbon dioxide concentration in the air under the saturation point can improve plant photosynthetic rate, reduce transpiration, inhibit plant respiration and significantly improve plant water use efficiency. Maintaining an appropriate carbon dioxide concentration is essential to promote carbon dioxide.
Fifth, the photosynthetic mechanism is affected by humidity, wind speed and so on. Excessive low stomatal conductance or high air relative humidity will reduce the stomatal conductance of plant leaves, increase the resistance of carbon dioxide entering the leaves and reduce the transpiration rate. Especially under the condition of low water and fertilizer supply, it is easy to lead to insufficient water and nutrition of plants and reduce the effect of increasing carbon dioxide. Wind speed will affect the uniform distribution of carbon dioxide in plant canopy and community, and affect the effect of increasing carbon dioxide application. Under the condition of sufficient water supply, high concentration carbon dioxide increased the stomatal conductance of soybean leaves and reduced water evaporation.
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