Design and application of LED light to simulate the light environment of crop intercropping population (Figure)

Intercropping is a method of planting two or more crops in the field by using the principle of biodiversity. China has a large population, and the per capita arable land area is decreasing. The intercropping and cultivation is common. The annual area is over 28 million hm2, which plays a key role in improving land utilization rate, increasing grain planting area and yield. A large number of studies have shown that intercropping between different types of crops not only improves crop population structure, improves resource utilization, enhances population resistance, but also reduces the application of chemical fertilizers and pesticides, while ensuring national food security and improvement. The market competitiveness of agricultural products has significant economic, ecological and social benefits. For example, in India, Southeast Asia, Latin America and Africa, the intercropping of cereal crops with legumes plays a crucial role in solving food and clothing problems.

The complementary utilization of light by different crops and the degree of competition affect the morphogenesis and yield formation of each crop within the intercropping complex. High-stalk crops (such as corn, sugar cane, etc.) preferentially absorb natural light, on the one hand, the light intensity in the lower part of the group is weakened, thereby reducing the photosynthetic rate of dwarf crops (such as soybeans, potatoes, etc.), reducing the accumulation of photosynthetic products, and ultimately affecting yield and Quality; on the other hand, changing the spectral composition, the ratio of red light to far red light decreased caused by the stem fund project: National Natural Science Foundation of China (31071373); National Key Basic Research and Development Project (2011CB100402); special source of modern soybean industrial technology system and Physiological and biochemical research. Chengdu, Sichuan Agricultural University, 611130.Email: ※ corresponding author lwgsy126.com: Yang Yu (1958-), male, Han nationality, Sichuan Englishman, professors, researchers from the physiological soybean cultivation. College of Agriculture, Sichuan Agricultural University, Chengdu, 611130. The stalk is excessively elongated, slender, weak, and the lodging is intensified. Therefore, to study the morphogenesis, physiological and biochemical processes, specific gene expression, substance absorption and accumulation, and utilization of light energy of different crops or genotypes in a special light environment within a complex intercropping group, to clarify the shade tolerance mechanism of crops. Breeding crop varieties suitable for intercropping and improving cultivation techniques are of great significance and are becoming a research hotspot in the field of agronomy.

The traditional method of simulating the light environment in a crop group is mainly to add one or more layers of green filter paper and shading net under common fluorescent lamps, so that although the light intensity and spectral composition can be changed, it is impossible to interplant the actual light in the field according to different crops. Strong and spectral composition, accurate simulation, and uneven illumination, large power consumption, it is difficult to meet the needs of intercropping physiological and biochemical mechanisms and molecular mechanisms. Light emitting diodes (LEDs) have many advantages such as high luminous efficiency, pure light quality, energy saving, long life and long wavelength, and can provide specific wavelengths according to the light characteristics of plants. It is expected to become a new light source for plant indoor cultivation in the future.

Based on the above viewpoints, this paper applies red, blue and far red three-color LED lamps to assemble and form a light source panel with continuously adjustable light intensity in each band. Taking the corn-soybean intercropping model as an example, the light environment in the crop intercropping complex group is simulated. And the effects of uniformity of light, spectral composition and the effects of two kinds of light environments on the growth of soybean seedlings were studied, in order to deeply study the physiological and biochemical mechanisms and molecular mechanisms of different crop varieties in response to intercropping. basis.

The design of 1 LED light source is an important part of effective photosynthetic radiation in natural light. Its strength plays an important role in crop photosynthesis and material accumulation. The far red light of 730nm has little significance for photosynthesis, but its strength and its intensity with 660nm red The ratio between light plays an important role in the formation of crop height and internode length. Within the crop population, the chlorophyll in the upper leaves absorbs the most in the red region (660 nm) and the blue region (450 nm), and the far red light absorption at 730 nm is small. Therefore, in the intercropping production system, the natural light phase The ratio of red-blue light to far-red light in the light environment in which the lower crop is located is reduced, and the degree is related to the cultivation specifications, crop types, and growth period. Therefore, in this paper, the above three colors of LED lamps will be combined in a certain proportion to form a light source panel with uniform intensity and proportion and uniform illumination, thus simulating the light environment inside the intercropping composite group.

The selection, proportion and arrangement method of LED lamps have a flashing frequency of 500 Hz; blue light uses LED lamps with a wavelength of 450 nm, the maximum power is 1.2 W, and the flicker frequency is 500 Hz; since it is difficult to purchase 730 nm high-power LED lamps on the market, In this paper, three low-power LED chips with a power of 0.14 W and a flicker frequency of 500 Hz are packaged into a single bracket to form a far-red LED lamp with a power of 0.42W.

In order to effectively simulate the effective photosynthetic intensity and the spectral ratio of each band in the composite group of natural light and intercropping, and to create a uniform light environment, the ratio of the three kinds of LED lights of blue light, red light and far red light is 1:3:3. That is, each LED board with a length of 270 mm is composed of 6 blue lights, 18 red lights and 18 far red lights, and the arrangement and the distance between the lamps and the lamps are as shown.

The main structure of the LED light source is composed of 10 LED panels, 4 fans, heat sinks, power supply, controller, adjustable hooks and other components. In this paper, aluminum, which is hard, strong and has good thermal conductivity, is used as the main structural frame of the light source. The components (hooks) with stress concentration are made of steel, and the frame structure is as shown.

The upper part of the light box is partitioned into four independent air ducts by an aluminum partition, and one end of each air duct is provided with an axial flow fan, and the other end is an air inlet, which communicates with the external environment. In this way, the cooling airflow enters the air passage from the air inlet and is discharged upward from the fan exhaust port, thereby taking away the heat radiated from the LED light panel. At the same time, an aluminum heat sink for increasing the heat dissipation area is installed in the air duct, and also serves as a structural reinforcing rib to increase the strength of the entire box. 1. Heat sink 2. Light board 3. Fan to prevent the heat dissipation air duct from being blocked or the fan is damaged, resulting in poor heat dissipation, etc. After the accident occurs, the temperature of the light board is too high and the LED light is damaged. This design is installed on the light source board (air duct) A high temperature protection device is arranged on the bottom partition. When the temperature of the light board exceeds the set value (usually 80 ° C), the device will automatically cut off the power of the entire lamp to protect the LED lamp bead.

The temperature protection device is a physical action of 2 metal sheets triggered by temperature, without any electronic components and software involved, and its work has high reliability and durability.

2 Application effect test 2.1 Materials and methods 2.1.1 Corn and soybean intercropping intercropping field light environment measurement According to the conventional cultivation method of producing corn and soybeans in southwestern China, corn was sown in early April, with a density of 420,0045,000 per hectare, using wide and narrow rows. Interval cultivation, wide row spacing 150cm, narrow row spacing 50cm, hole spacing 4550cm, 2 seedlings per hole. When the corn grows to the big bell stage (ie from late May to early June), soy is sown in the corn wide line, and the wide line is measured with the Dutch-made Eventis plot (model: AvaField-1). Spectral map at a distance of 10 cm from the ground (75 cm from corn), 20 points with a spacing of 15 cm were measured, and the software automatically calculated the average value.

2.1.2 Application of LED light source to simulate the field light environment According to the above method, two independently controlled and identical LED light sources were fabricated and mounted on a plant tissue culture rack. According to the spectral measurement results of 2.1.1, three kinds of controllers were adjusted by the controller. The radiant intensity of a color LED light. One of the light sources is used to simulate a natural light environment; the other is used to simulate a shaded light environment within a crop composite population. At the same time, the flicker frequency of the two light source plates was set to 500 Hz on the controller, and the photoperiod was 13 h during the day and 11 h at night. Soybeans were planted in plastic culture rafts with height and diameter of 10 cm. The culture medium was vermiculite and Perlite (1:1). Water is immersed daily to maintain a substrate moisture content of around 75%, and 1/2Horland broth is poured once a week. Three plants per pot were cultured in two LED lighting environments. The ambient temperature of the culture chamber was 25 ° C and the air humidity was 70%. Each treatment was repeated 3 times with 8 pots per replicate. With the increase of soybean plant height, the height of the light source plate is adjusted, so that the distance between the LED lamp beads of the two light sources and the top of the soybean plant is always kept at 10 cm, thereby ensuring that the received light intensity and light quality are not in the whole growth process of the plant. change.

2.1.3 Relevant indicators Determination The spectral composition, radiation intensity and uniformity of the LED light source designed by the spectral measurement of the ground object.

When the soybeans cultured in the two light environments were grown to a single stage (the first compound leaf full exhibition), the plant height, stem diameter, leaf area, root and leaf fresh quality and dry quality were measured, and the anti-falling test was used. The bending resistance in the middle of the hypocotyl. SPSS13.0 statistical analysis software was used to analyze the difference significance by T test.

2.2 Test results 2.2.1 Corn and soybean intercropping intercropping in the field Light environment The actual light environment in which soybeans are embedded in the composite group is an important basis for the application of LED artificial light source to simulate the light environment. Field field measurements showed that the shading of corn reduced the photosynthetically active radiation intensity of inter-row soybeans to 25.96% of natural light; due to the difference in absorption rate of different bands in the spectrum, the blue light, red light and far The transmittance of red light is different, and the difference in radiation intensity and transmittance between blue light and red light is not significant. The radiation intensity of far red light is significantly lower than that of blue light and red light, but the light transmittance is higher than both. Therefore, the light environment of soybean is lower than the total light, and the ratio of far red light is reduced. Increase (Figure 1 natural light and corn line 2 kinds of radiation intensity comparison of each band Table1Contrastoflight (average of 20 points, unit pm-2.nm-1) light environment far red light (730nm) total photosynthetically active radiation (blue light + Red light) Natural light corn inter-line transmittance /% Note: Different uppercase letters in the same column indicate a very significant level of difference of 1% between treatments, the same below.

The effect of LED light source to simulate the field light environment is based on the actual light environment parameters of 2.2.1 corn soybeans in the field, and the blue, red and far red light intensity of A and B LED light sources are set, 10 cm away from the LED lamp beads. The spectrogram was determined by spectroscopic spectroscopy. The results show that the LED light source designed in this paper can simulate the natural light environment and intercropping in the field, and the representative groups of 450 nm (blue light), (red light) and 730 nm (far red light) in the crop composite group are representative. Crop photosynthesis and morphogenesis have important spectral components.

Plants used for the study of crop molecular and physiological mechanisms require uniform growth, so it is particularly important to create a relatively uniform light environment within a certain range. In order to investigate the uniformity of the wavelengths under the light source plate, 11 points with a spacing of 10.5 cm were taken on the two diagonal lines of the rectangular light source plate, and the radiation intensities of the three bands of 450, 660 and 730 nm were measured and repeated five times. As shown, in each band, except for the weaker radiant intensity at the two points on the side, the radiant intensity changes in the middle nine points are extremely small, indicating that the light in the three bands is distributed in the rectangular area of 50 cm×80 cm of the culture frame. Evenly.

Spectral composition of different points on the diagonal of the LED light source The growth of soybean under different LED artificial light sources can be seen from Table 2. Under the shaded light environment simulated by the three-color LED light, the plant height and leaf area of the soybean are Stem dry weight and other indicators increased significantly, while leaf dry mass, specific leaf quality, root dry weight, root-shoot ratio and leaf SPAD value decreased significantly, plant strain showed slender, photosynthetic capacity decreased, head (stem) heavy foot (root) Light, and the strength of the stem is reduced, easy to fall, which is a typical shade-free reaction of plants in a shaded environment.

It can be seen from the above growth characteristics of soybean in two simulated light environments that the LED lamp designed in this paper successfully simulates the light environment in the soybean-soybean intercropping process, in order to further study the intercropping of different crop varieties. The basis of the physiological and biochemical mechanism and molecular mechanism of interplanting stress response.

Table 2 Effect of LED light source simulation intercropping light environment on soybean growth LED light source plant height stem diameter per plant leaf area per 10 leaf dry mass / g than leaf weight simulation natural light simulation shading stress LED light source for every 10 stems per 10 strains Root-root crown-to-leaf SPAD stalk flexural mass/g (dry mass ratio) value force/N simulated natural light simulation shading stress 3 Conclusion Fluorescent lamps commonly used in indoor plant cultivation are cold light sources, and their spectral composition does not require plants. The yellow light and green light are many, and the red light and far red light of the key crops for plant growth and development are very small and cannot be used to simulate the actual light environment in the crop field. According to the demand characteristics of crops for light and the characteristics of intercropping field light environment, the blue, red and far red three-color high-power LED lamps are used for assembly. The special lamps for simulating the light environment in the crop field are pure. The light is evenly distributed, and the light intensity of each color light can be adjusted as needed. In practical application, according to the method and idea of simulating corn-soybean intercropping field light environment, the above lamps can be used to simulate intercropping of different crops and field light environment in different stages of crop growth, and cultivate crops indoors to carry out physiological and biochemical analysis.

Among all the light sources currently used, although LED is the most energy-efficient, in order to meet the light intensity requirements of crop growth, lighting equipment usually consists of tens to hundreds of LED lamp beads, and its total power is hundreds of watts. The highest photoelectric efficiency of LED devices is calculated at 20%, and 80% of the electrical energy is still converted into heat. Improper heat dissipation can seriously affect the service life of LED lamps. In this paper, the combination of heat sink, air duct and fan is adopted. The heat dissipation effect is good, and the high temperature protection device is used. The lamp bead is safe to use and has a long service life.

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