The effect of LED plant light quality on plant seed germination and root growth
The effect of LED light quality on the growth of crop roots. In herb plants, light can pass through the internal light environment and be regulated by photoreceptors from the ground to the roots and regulate their growth and development. Although the root system does not directly receive the light bar, it responds differently to different light qualities. LED blue light is beneficial to the growth and development of plant roots. Blue light can increase the root vigor, total absorption area and active absorption area of seedlings. Irradiating the cultivated rice seedlings with LED blue light, it is found that the accumulated protein content in the root system of the rice seedlings is high, the non-protein nitrogen content is low, the ratio of protein to nitrogen to total nitrogen is high, and the total nitrogen content is also high, indicating that the LED blue light can increase the root nitrides of the rice seedlings. The synthesis and production of protein accumulate in the root system. At present, seedling raising based on the LED blue light effect of crop roots has been applied by reproducers.
The effect of LED plant light quality on leaf growth, leaves are the main organs of plants for photosynthesis, and the change of LED light quality directly affects leaf growth. According to reports, the leaf area of birch seedlings grown under blue light is twice that of seedlings under red light, and the area of leaf epidermal cells, palisade tissue, sponge tissue and functional chloroplasts are larger than those under white and red light. The rice seedling experiment has the same result. Compared with white light, blue light can obviously promote the growth of rice seedling leaves, increase the angle between the leaf and the sheath, and make the leaves flat; while the effect of red light is opposite, it inhibits the increase of leaves. Wide growth. However, some people think that the compound light is more conducive to the growth and development of the leaves. The leaf area of lettuce under the combined light of red, blue, and green is the largest, followed by white light, and finally red and blue light. Studies have also shown that increasing the proportion of LED red light in the compound light has a certain promotion effect on the increase of tobacco leaf area, but the leaf weight of the leaf is reduced, and the leaf becomes very thin.
The influence of the light quality of LED plants on the regulation of stomatal organs. Stomata are the channels for water and oxygen to enter and exit, and are the gateway to plant photosynthesis. Stomatal movement is regulated by many external environmental factors and internal factors, of which light is an important regulating factor. It has been found in both monocot and dicot plants that LED blue light can promote the opening of stomata, and green light can reverse this effect. They believe that the reversible reaction of blue and green light leading to the opening and closing of air puncture may be derived from zeaxanthin Two kinds of isomerization, namely the physiologically active body that mainly absorbs green light and the inactive body that absorbs blue light. The principle that LED blue light promotes the constant opening of stomata, that is, the blue light activates the plasma membrane ATPase to continuously pump out protons to form a transmembrane electrochemical gradient, that is, the power of K+ through the K+ channel, thereby promoting the absorption of K+ by the guard cell, resulting in intracellular osmotic potential When descending, the guard cell swells by absorbing water and the stomata open. Under blue light, the malic acid in the guard cells increased to 173% of the original within 30 minutes, and the sugar content increased to 215% after 2 hours. The starch hydrolysate maltose and maltotriose also continued to increase; while under red light, the guard The organic acids and maltose of the cells increased very little, while the sucrose rose to 208% of the original within 2 hours.
The effect of LED plant light quality on the growth of crop stems, different wavelengths of light can regulate the growth of stems by affecting the level of endogenous hormones in the plant. Violet light can increase the activity of indole acetic acid oxidase and reduce the level of auxin (IAA), thereby inhibiting plant growth. At the molecular structure level, red light can promote cell elongation, while blue light has the opposite effect. In general, the long-wavelength LED red light promotes the elongation of the stem, while the short-wavelength light (blue light) inhibits the elongation of the stem.
The effect of LED plant lights on the germination of plant seeds. When the seeds absorb water, their germination is often affected by light. The germination of light-demanding seeds is jointly regulated by PhyA and PhyB. The promoting effect of LED red light on seed germination is mainly regulated by PhyB, and the main function of phyb is to sense changes in the ratio of r/fr. Whether the seed can fully germinate and grow is mainly determined by the R/FR ratio of the light it receives subsequently. A lower R/FR ratio inhibits the germination of the seed. Cucumber seeds can germinate under the blue light of LED, but the continuous irradiation of red light inhibits the germination of cucumber seeds. Under the light quality that can promote germination, the peroxidase activity in the seeds increases with time, and becomes stable after the cotyledon opens: under the LED light quality that inhibits germination, the peroxidase activity in the seeds is always Keep it low.
