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          Application and prospect of LED in in vitro culture of plants

          A light-emitting diode (LED) is a new type of light source that converts electrical energy into visible light. In the 1980s, LED was first applied to plant facility cultivation experiments [1]. Since then, it has been gradually applied to the experiments of light-formation and photosynthesis of plants on the mechanism of light on plant mechanisms [2, 3], in plant life science research. The field is getting more and more attention. In vitro culture of plants refers to a technique for in vitro culture of plant organs, tissues, cells or protoplasts under sterile conditions to regenerate cells or whole plants [4], which has been developed for decades, including Many new technologies, such as cold cathode fluorescent lamps (CCLF) [5], sugar-free tissue culture techniques [6], and open tissue culture techniques [7-9] have been applied. At present, ordinary artificial light sources such as fluorescent lamps and high-pressure sodium lamps widely used in in vitro culture of plants have certain limitations, and LEDs have excellent characteristics that these light sources do not have, so people try to replace these ordinary artificial light sources with LEDs. Studies on potato [10], Phalaenopsis [11], and rapeseed [12] have shown that LED can be used as an ideal source for plant in vitro culture. In addition, many scholars at home and abroad have optimized and improved LEDs to further adapt LEDs to the light source characteristics of test tube plants [13 - 15]. With the development of photobiology technology, the application of LED in different plant in vitro culture has become a hot issue and has a good application prospect.

          1 LED application to the advantages of plant in vitro culture

          The LED was born in the 1960s, and its core is a P-N-structured wafer consisting of a P-layer formed by a P-type semiconductor and an N-layer formed by an N-type semiconductor and a heterostructure in the middle. The N region is enriched with a large number of free electrons. When current flows through the wire through the wire, electrons move from the N layer to the P layer, and the P - N junction recombines with the holes, and the energy is released in the form of radiated visible light.

          At present, fluorescent lamps and fluorescent lamps used for in vitro culture of plants generally have undesirable effects such as short service life, easy damage, impure light quality, easy heat generation, and low plant absorption rate. LED has the characteristics of low power consumption, small size, cold light source, good monochromaticity and long life [18-20]. Compared with ordinary artificial light sources, LED has many advantages in plant in vitro culture. (1) Low energy consumption. Under ordinary light source conditions, the electricity cost for plant in vitro culture usually accounts for 40% - 50% of the total cost [21], while the same light effect, LED light source consumes only about 1 / 8 of the ordinary light source, 1 of the fluorescent light /2 [22]. If LEDs are used in large quantities for plant in vitro culture, the energy and cost savings will not be overlooked. (2) Small size. The LED is small in size, convenient for routine repair and maintenance, and can be directly installed above the culture container, which increases the effective utilization space of the culture chamber. Multiple culture layers can be set up for three-dimensional culture to realize small intensive production of plant in vitro culture. (3) Cold light source characteristics. The LED is almost non-heating, which facilitates the temperature control of the culture chamber, reduces the cooling cost, further reduces the cost, and the light source does not cause condensation on the bottle wall when the light source is irradiated close to the plant, and the plant can be prevented from burning or even dying due to excessive temperature. (4) Good monochromaticity and high purity of light quality. Ordinary artificial light sources have a wide range of radiation spectrum, and the light effect of plants has certain requirements on the wavelength of the light source, so the utilization efficiency of plants is often low. The half-wave width of the LED light source is about ?± 20 nm. After selecting the light source according to different plant requirements, the spectral absorption peak of the LED is almost the same as the wavelength of the plant required [23, 24], and the biological performance is better. (5) Not easy to damage and long life. LED has a much longer service life than ordinary artificial light sources, and has good seismic resistance, is not easy to damage, reduces maintenance and replacement, saves costs, and reduces waste pollution. (6) Adjustability of light intensity and light quality. By changing the magnitude of the introduced current, the LED can directly adjust the light intensity and light quality, and facilitate the regulation of different illumination conditions in plant in vitro culture.

          2 LED application in plant in vitro culture

          Light is an important environmental factor affecting plant growth. The optical effects of plant growth and development are related to the light quality, light intensity and photoperiod of the light source. Different light qualities can affect plant organ differentiation and cell division [25]; different light intensity affects plant photosynthesis by affecting plant growth; while photoperiod affects plant flowering [26]. At present, there are many applications of LEDs in studying the effects of different light qualities and light intensity on test tube plants, and less use in studying photoperiod effects. 2.1 The effect of LED light quality on plant in vitro culture The traditional light source used by different light qualities on plant in vitro culture is often selected according to the human eye's adaptability to light. These lights are not monochromatic light with only a single wavelength. The spectral range is usually not commensurate with the demand of test tube plants. The absorption rate of test tube seedlings is low, and it is difficult to determine the wavelength that best matches the biological characteristics [27]. Therefore, filters and suction filters are often used in previous experiments. The monochromator and the like narrow the spectrum of the light source, but its operation is complicated, the light quantity is low, and the spectrum cannot be accurately quantified, which easily affects the accuracy and comparability of the experiment [28]. Since LED can better compensate for these shortcomings, the use of LED to study the effects of different light qualities on plant in vitro culture has become an important technology. 2.1.1 Effect on the proliferation of test-tube seedlings Yang Changjuan et al [29] used LED combined light source to study the effect of different light quality on the proliferation of test tube seedlings of Eustoma. The results showed that the ratio of LED red and blue light was 2:1, and the proliferation rate of test tube seedlings was the highest. Yan Xiuru et al [30], Zhang Huan et al [31] study on chrysanthemum tube seedlings showed that the composite light formed by different light quality LED combinations significantly improved the proliferation effect of test tube seedlings. These results all indicate that LED complex color light can promote the proliferation of test tube seedlings, which may be because different light qualities affect the differentiation and degree of plant organ differentiation, and compared with monochromatic light, complex color light contains different light quality components, and each other Complement each other to increase the rate of proliferation.

          2.1.2 Effect on the growth of test-tube seedlings Lian et al [32] showed that LED red-blue composite light is most beneficial to the growth of lily tube seedlings. Nhutet al [33] found that strawberry tube seedlings grew better when exposed to red and blue light of 7:3. These findings are consistent with the results obtained by Shin et al [34] in the photochemical ex vivo test of Dolly Phalaenopsis. In general, the combination of different quality LEDs in a test tube seedling is more conducive to the growth of test tube seedlings than the use of LED monochromatic light treatment, which may be related to the imbalance of light energy distribution that the monochromatic light causes the system to utilize. 2.1.3 Effects on the contents of in vitro plantlets When studying the effects of different light-emitting LEDs on the synthesis of in vitro plant material, Jao et al [35] found that the increase in chlorophyll content of calla seedlings in LED blue light was significant. Dai Yanjiao Etc. [36] also showed through experiments that LED monochromatic blue light is beneficial to the synthesis of soluble protein, starch and free amino acids in Phalaenopsis tube seedlings. However, the views of Yang Hongfei et al [37, 38] are significantly different from those of the former two. The experiment of culturing the test tube seedlings of the stalks with LEDs of different light quality ratios shows that the ratio of LED red and blue light 1:1 is beneficial to the starch. And the synthesis of soluble proteins. The formation of this difference may be related to the different test materials. On the other hand, LED blue light has a positive effect on the synthesis of various substances in test tube plants, and the specific effects on different inclusions are different. 2.1.4 Influence on the formation of test tube seedlings Wei Xing et al [39] showed that a single LED red light is easy to cause the leaves of the chrysanthemum tube seedlings to grow, and the LED blue light is short and strong. The same chrysanthemum as the research material, Guo Weiwei et al [40] study shows that LED red, blue light 9: 4, is conducive to gerbera test tube seedlings dwarf; red, blue light 3: 1, when the ordinary chrysanthemum test tube seedlings dwarf effect better. The above shows that the effect of different light quality LEDs on the morphology of test-tube seedlings is mainly reflected in the red light LED to promote plant growth and photomorphogenesis, while the blue LED inhibits plant elongation, which is related to Liu Jinfeng et al. [41], Cybularz-urban et al The test results of [42] are more consistent.

          2.1.5 Impact on callus Callus culture is an important part of plant in vitro culture. Many scholars have explored the role of different light quality on wound tissue [43, 44], and with LED In the application of plant in vitro culture, some scholars have used LED instead of ordinary light source for callus test. Luo Liyuan et al. [45] treatment of grape callus with different light-emitting LEDs showed that red LEDs promoted the growth of grape callus but inhibited the synthesis of resveratrol, while blue LEDs did not affect callus. Growing, but increased the content of resveratrol. After the fine-tuning of LED light quality, in the study of garlic callus, Ma Lin et al [46] also found that red LEDs promote callus differentiation, while blue LEDs inhibit callus differentiation. It can be seen that the choice of light quality plays a decisive role in the growth of callus.

          2.2 Effect of LED light intensity on in vitro culture of plants

          In general, when the environmental conditions are appropriate, if the light intensity is below the light saturation point of the plant, the photosynthesis of the plant is inhibited, and the light intensity is increased accordingly. The photosynthesis of the plant is strengthened. When the light saturation point is reached, the light intensity is continuously increased. Plant growth does not change significantly, but may have adverse effects. In the in vitro culture of plants, the use of LED light intensity controllability, many people have used LED for the study of the light intensity characteristics of test tube plants.

          In the experiment of the effect of different light intensity on the growth of test tube plants, Yang Yating et al. [47] found that the sweet potato tube seedlings grew optimally when the LED red-blue composite light intensity was 22.50 ??mol?·m -2?·s -1 , and other treatment groups. There are big differences. Yan Xinfang [48] also used LED new light source culture rack to carry out related experiments and showed that the combination of LED red and blue light intensity is 70 ??mol?·m -2?·s -1 , which is most beneficial to the growth of peony tube seedlings. Kurilcik et al [49] showed that the growth of grapes was best when the LED composite light intensity was 45 - 55 ??mol?·m -2?·s -1 . Comparing the three, it can be found that the optimal growth of plants is sensitive to light intensity and adaptability, and is related to the species itself.

          In the same kind of plants, Kurilicik et al [50] found that the LED composite light grew best under the light intensity of 40 ??mol?·m -2?·s -1 . Zhang et al. [51] showed that when the LED light intensity is 60 ??mol?·m -2?·s -1 , the condition of chrysanthemum tube seedlings is better, and the growth in all aspects is more consistent.

          Light intensity mainly affects the photosynthesis of test tube plants, and the strength of photosynthesis can also be measured indirectly through changes in plant vegetative organs. Nhut et al [52, 53] found that the suitable red-blue color combination of LEDs, when the light intensity is 60 ??mol?·m -2?·s -1 , the fresh weight of the rhizome of the plant tube seedlings reaches the maximum, while the light intensity is 60 ??mol. ?· m - 2 ?· s - 1 , banana tube plant roots fresh weight maximum. In the study of external factors affecting plant growth, the application of LEDs with separate light intensity can be used to study the effects of different illuminances on photosynthesis of isolated tube seedlings.

          2.3 Effect of LED photoperiod on plant in vitro culture

          At present, there are relatively few studies on the photoperiod effect of test tube plants. Jao et al [54] using LED red blue light (photoperiod 16 h / night 8 h) alternately irradiated potato tube seedlings showed that the effects of the two treatments on potato tube seedlings were different, and the dry weight of potato tube seedlings illuminated by LED red and blue light Significantly higher than the alternately treated tube seedlings. It was also confirmed that the coexistence of light with different spectra is a necessary condition for optimal growth of test tube plants.

          3 Problems and prospects

          3.1 Problems

          At present, there are still some problems in the application of LED in in vitro culture of plants. First, because of the high price, LEDs cannot be fully promoted. The core component of LED--the cost of the chip accounts for a large proportion of the total cost, while the high-end LED chips in China are mostly from abroad, resulting in high LED prices. The high cost limits the application of LED in the industrial production of plant in vitro culture, but LED is still an important application tool in scientific research [55]. Moreover, the defects of LED itself also limit its application in plant in vitro culture to some extent. LEDs have stringent requirements for the heat dissipation of their P-N junctions. The LED is a cold light source, and the heat resistance of the chip is limited. However, a small part of the electric energy still forms heat radiation during the working process. If the heat is concentrated in a small area, the aging of the chip is accelerated, which will aggravate the light decay [56, 57]. The service life is greatly reduced. In addition, the LED light source has the stability of light quality and the uniformity of chromaticity and brightness [58], which still needs further improvement.

          3.2 Prospects

          With the development of modern optoelectronic technology, LED production technology level and structural materials will inevitably be continuously improved and updated, thereby reducing its production cost and further optimizing performance, while overcoming the existing defects, making LED more suitable for the light source requirements of plant in vitro culture.

          When studying the effects of light quality and light intensity on the in vitro culture of plants, LEDs have monochromaticity, and it is possible to eliminate gratings or monochromators, and obtain accurate high-purity light sources to improve the results of photobiology experiments. Accuracy and science.

          The LED is small in size and low in power consumption, which is beneficial to its application in conventional plant in vitro culture. At this stage, there are few reports on the application of LEDs to conventional plant in vitro culture, and there are many deficiencies in commonly used light source devices. It is more urgent to replace these common light source devices with more efficient LEDs. A new culture chamber using an LED light source can directly mount the light-emitting element above the culture vessel and use the remaining space to set up more culture layers. As the problem of stability and uniformity of the LED source is overcome, the illumination received by the plants at different culture locations will also be consistent. The new culture room constructed by LED can realize the expansion of utilization space, increase the number of cultures, reduce the cost of electricity, promote the consistent growth of plants, increase the growth rate of plants, and save energy and environmental protection. The individual controllability of LED illumination will also be better applied in conventional plant in vitro culture. Different plant species, the light-receiving characteristics of different growth stages of the same plant, and the appropriate light source required to change the single shape of the test-tube seedlings, such as the induction of in vitro culture and the rooting of the seedlings, the best artificial light source selected Inconsistent, the uniform light source used in the conventional culture room does not provide optimal illumination conditions for plant growth, and this demand will become possible in the new LED culture room. The LED can regulate the radiation by controlling the current. Therefore, the LED can emit different light in different growth stages of different test tube culture zones, different treatment zones and test tube plants, so that the illumination is more targeted. Improve the effect of plant in vitro culture and the accuracy of the experiment. In vitro culture of plants is affected by many environmental factors. Therefore, it is necessary to simultaneously improve other growth conditions of plants, and the application of LEDs and culture chambers CO2 / O2

          Concentration is combined with control, humidity setting, nutrient composition of the medium, and adjustment of hormone levels to meet the needs of test tube plants and improve the use of LEDs. With the further serialization and standardization of modern in vitro culture technology, LED can be combined with new technologies such as CCLF, sugar-free tissue culture technology and open tissue culture technology to further develop plant in vitro culture through multiple adjustments. In short, with the advancement of the LED industry and the improvement of in vitro culture techniques, the large-scale application of LEDs to plant in vitro culture will become a trend.

          Edit: Nizi

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          亚洲 欧美 图片 自拍 视频
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