The influence of light quality of artificial grow light on photosynthesis and light morphogenesis
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 visible light that human eyes can see. This is the photosynthesis energy and environmental signal, which affects the growth and development and yield quality of plants through photosynthesis and photomorphogenesis.
First, photosynthesis is the basis 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, and shade response. Only part of the light in the sun’s full-color spectrum is absorbed by plants to produce photosynthesis. The morphology of the leaves of plants and the physiological responses of plants will affect photosynthesis.
Second, photomorphogenesis refers to the process by which light acts on plants as environmental signals to regulate plant growth, differentiation and development. The light-receiving receptors are low in plant cells, but they are very sensitive to changes in the external light environment. According to cultivation research, grow light with the 600~700nm red wavelength promotes the germination of lettuce seeds, while grow light with the 720~740nm far red wavelength inhibits the germination of lettuce seeds.
2-What does “light fertilizer” mean?
Plants use a variety of different wavelengths for photosynthesis, which means that plants are selective to the spectrum. The photosynthesis of plants absorbs about 60% of the light energy in the visible light spectrum (380~760nm), of which the wavelength is 610~720nm The red-orange light (the wave peak is 660nm) and the blue-violet light of 400~510nm (the wave peak is 450nm) are the absorption peak areas, and these two wavelength bands become the “light fertilizer” of plants.
LED grow light can emit monochromatic light required for plant growth, and the combination of monochromatic light can form the spectrum required for plant photosynthesis and morphogenesis. LED plant grow light source can improve the light energy utilization rate of plants.
3-What is a photosynthetic organs and how is it affected?
Broadly speaking, the light and mechanism refers to the mechanism that can carry out partial or complete reactions of photosynthesis, ranging from chloroplasts and thylakoids, to mesophyll cells, leaf organs, and even the entire plant body. The narrow sense is chloroplast.
First, the photosynthetic machinery is affected by light adversity. Too strong or weak light will cause light stress in plants, inhibit photosynthesis, and reduce photosynthetic efficiency. Weak light leads to yellowing, and plants produce active oxygen free radicals under strong light, resulting in photoinhibition.
Second, the photosynthetic machinery is affected by temperature. Periodic changes in temperature affect plant photosynthetic carbon fixation, reduction, sucrose synthesis, transportation and distribution of photosynthetic products, and electron transfer.
Third, photosynthetic institutions are affected by nutrient supply. Nitrogen nutrition is the basis of plant life. The correlation coefficient between leaf photosynthetic capacity and nitrogen content is 0.9 on average. The photosynthetic rate of light saturation increases 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 machinery.
Fourth, the photosynthetic apparatus is affected by carbon dioxide. Carbon dioxide is the main raw material for photosynthesis. The increase of carbon dioxide concentration in the air below the saturation point can increase the photosynthetic rate of plants, 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 apparatus is affected by humidity and wind speed. Over-proportioned low stomatal conductance or excessively high air relative humidity will reduce the stomatal conductance of plant leaves, increase the resistance of carbon dioxide to enter the leaves, and reduce the transpiration rate. Especially under the condition of low water and fertilizer supply, it is easy to cause insufficient water nutrition in plants and reduce the increase The effect of carbon dioxide. The wind speed will affect the uniform distribution of carbon dioxide in the plant canopy and the community, and affect the effect of increasing carbon dioxide. With sufficient water supply, high-concentration carbon dioxide increases the stomatal conductance of soybean leaves and reduces water evaporation.