The concept of plant chemosensitivity (Allelopathy) was first proposed by Molisch in 1937 and defined as the interaction of biochemicals between all types of plants (including microorganisms), which includes both harmful and beneficial aspects. Besides, Molisch failed to further clarify the specific content of plant chemosensitization research, and in the mid-1970s, Rice, based on Molisch's original definition and the results of nearly 40 years of research on plant chemosensitization, defined plant chemosensitization as: plants (including microorganisms) release chemicals into the environment and produce direct or indirect harmful effects on other plants. This definition clarifies for the first time the role of plant chemosensitivity. This definition clarified for the first time that the essence of plant chemosensitivity is that plants affect neighboring plants by releasing chemicals into the environment. Subsequently, research on plant chemosensitization has been very active and has yielded many results. The chemicals released by plants were found to be harmful to plants, but also beneficial in many cases. At the same time, in the agricultural and forestry production practice and research, it has been found one after another that the continuous cropping obstacles of many crops and the decline of plantation forests are due to the result of the toxicity of chemical substances released by crops or forest trees to themselves, thus revealing that plant chemosensitization can be carried out in interspecies as well as intraspecies. in the mid-1980s, Rice added the beneficial effect and self-toxicity to the definition of plant chemosensitization. Since then, Rice's definition of plant chemosensitization has been generally accepted. The media of plant chemosensitization are chemical substances, which are called "Allelochemicals". Allelochemicals, as mentioned by Kong Chuihua, are chemical substances produced by plants that affect the growth, behavior and population biology of other organisms, including not only inter-plant chemical substances, but also plant-animal chemical substances, which are not required to enter the environment, but can be carried out in the body as well. It has been found that many chemosensory substances act not only on plants but also on microorganisms, animals and especially insects. Plant chemosensors must have suitable pathways into the environment, and in natural conditions there are four main pathways. Root secretion Root secretion produced by metabolism can be primary metabolism and secondary metabolites. A large portion of the root secretions of secondary metabolites are chemosensory substances. For example, the black walnut tree (UIansnigra) can secrete the toxic walnut quinone (Juglone), which can inhibit the germination of other plant seeds when the concentration of walnut quinone is 20μg/ml. Volatile chemical substances produced by the stem and leaves of plants such as lemon eucalyptus (Eucalyptus citriodor Hook) leaves volatilized pinene and other chemosensory substances, can strongly inhibit the germination of radish (Raphanus sativus) seeds. Plant aboveground by rain, fog and dew drenched chemical substances such as eucalyptus (Eucalyptus) leaves washed down by the water of the chemosensory substances are mainly phenols, they have a significant inhibitory effect on the growth of flax (Linum spp.). Microorganisms decompose plant residues and release the chemical substances into the soil such as ferns (Pteridium aquilinum) plant chemosensory substances are released from the dead branches and leaves. Use of chemosensory control of weeds The mulching of fields with chemosensory plant residues is effective in controlling weeds. After mulching with plant residues, the mulching residues affect the germination of weed seeds by competing with weeds for light, nutrients, water, and chemosensory substances released by the residues. It has been reported that as of 2000 approximately 20% of the cropland in the United States was being returned to the soil using straw, which means that post-harvest straw will remain in the topsoil. It was found that post-harvest barley, oat, and wheat residues inhibited the growth of weeds the following year.Putnam et al. found that rye planted in vegetable fields and orchards in October and glyphosate used in the spring to kill the rye, rye mulch was effective in controlling the growth of weeds and confirmed that the chemosensitizing agent was a chemical substance called hydroxamic acids. Putnam et al. found that sorghum residue had a significant weed control ability, and Alsaadawi et al. found that sorghum root secretions significantly inhibited seed germination and seedling growth of quinoa in a sand cultivation test. Another test showed that 5% to 10% concentration of aqueous extract of rice stubble and straw mixture inhibited weed germination and seedling growth, and the different inhibitory effects might be due to different phenolic concentrations in different parts of the plant. The effects of aqueous extracts on weed stem elongation and dry matter mass were similar, but the inhibitory effect on root elongation was greater than that on dry matter mass, and the inhibitory effect on grass weeds was greater than that on broad grass weeds. Different plants with chemosensory effects produce different chemosensory substances, each with its own specific inhibitory targets. Sunflower can effectively inhibit the growth of weeds such as amaranth, cranberry, Li and petunia, and some varieties of oats can inhibit the top growth of mustard weeds, and the height of the inhibited weeds is only 1/3 of the control. 1983 Leather used sunflower and oats to rotate the results of the rotational crop proved that the rotational crop area of the density of weeds is significantly smaller than their respective monoculture area, indicating that each of the two crops play different weed control functions, relatively improve the weed control. weed control functions, relatively improving the effectiveness of weed control. The chemosensory effect released by winter wheat can inhibit the growth of white weeds, and the crop rotation of winter wheat and other crops can inhibit or control the damage of white weeds in the farmland with a lot of growth of white weeds. Some countries in the world (such as Japan, Korea, Thailand, Egypt, etc.) have researched the weed suppression through crop rotation, which can reduce the use of chemical herbicides and improve crop yield. Utilization of companion plants Some plants have selective chemosensitization, which can inhibit the growth of certain weeds without harming the growth of crops. Mexican marigolds have a strong toxic effect on weeds with starch in the roots, such as the roots of upright elderberry with browning and turning into empty shells in the shape of acid corrosion, and this phenomenon can be seen even in places farther away from the marigolds. Putting water plantain in the water field where water hyacinth is more harmful can quickly make water hyacinth show symptoms such as fading green, leaf rot, blackening of roots, and finally death. This kind of companion plant can and crop **** exist in a particular area, and play the role of weed control, it is necessary to carry out in-depth research. Extraction of chemosensory substances and synthesis of new herbicides By extracting, isolating and identifying chemosensory substances and simulating their structures, natural selective herbicides can be developed, which can reduce the use of chemical pesticides. As the natural herbicides synthesized by biological pathway have the characteristics of low toxicity and high efficiency, easy absorption and degradation, and specific target, they can reduce the pressure of agricultural production on the environment, lower the residual amount of chemical pesticides in crops, and contribute to the development of eco-agriculture and the realization of the strategy of sustainable development of agriculture. In this regard, there have been examples of successful synthesis of biopesticides, such as by Zhenguo to the desert plants produced by the chemosensory substances 1,8 - eucalyptus brain as a precursor, the development of a new type of successful systemic herbicide Cin-methlin (Cin-methlin), has been applied to rice, peanuts, soybeans, cotton and other crops; Fujii Yoshiharu, etc., according to the cotton root secretion of the one-legged gold mengtin synthesized by the one-legged golden phenol has been applied to the prevention and eradication of soybeans, peanuts, The synthesis of monocotyledonol by Yoshiharu Fujii et al. based on monocotyledonin, a root secretion of cotton, has been used to prevent the parasitic weed monocotyledonin in soybean, peanut, corn, and sugarcane. Transgenic breeding Breeding that combines a chemosensitive trait into a crop variety to enhance the competitive advantage of the crop to suppress certain major weeds. It is possible to introduce chemosensitive genes into cultivars using conventional hybridization techniques, or biotechnological means such as protoplast fusion, to produce crop varieties for specific regions that are resistant to certain weeds. After clarifying the genetic behavior and mechanism controlling crop chemosensitivity, biotechnology and genetic engineering can be used to introduce genes controlling chemosensitive traits into the genomes of productive and high-quality crop varieties, and to breed excellent crop varieties that can achieve both high yield, high quality and high efficiency, and can automatically suppress weeds under field conditions. At present, the breeding of weed-resistant crop varieties is still in its infancy, Dilday hypothesized that the genes controlling crop yield and some other excellent traits in the rice genome and the genes controlling chemosensitization are weakly interlinked, which creates conditions for the breeding of high-yield and high-quality rice varieties with enhanced chemosensitization. High chemosensory ability is reported to be present in the wild type of the crop, which has been lost due to emphasis on traits such as high yield in breeding. Plant resistance to insects and diseases can be integrated into crop varieties through hybridization with wild species. However, for chemosensory breeding currently only in rice, varieties with high chemosensory ability to suppress weeds have been obtained. In addition, Haan et al. crossed dwarf seed rape with nodulating cabbage to obtain a hybrid with weed suppression and the dwarfed Brassica lines germinated well in corn and soybean rows and suppressed weeds for 28-42 d without any effect on the crop. The discovery by Panchuk et al. of a hybrid of icterocarpus spp. and wheat that displays icterocarpus characteristics and high suppressive activity is certainly a good start. If new varieties of wheat, rice and some other major crops can be successfully developed for weed suppression in the future, not only the use of herbicides can be reduced, but also yields can be expected to be further increased. Prospects for the application of chemosensitivity in weed control The use of chemosensitivity to control weeds is a promising new avenue. Since this control measure takes advantage of the plant's own defense system or resilience in the ecosystem, does not introduce difficult-to-degrade chemicals into the system, and does not bring about environmental problems such as pesticide residues, the use of chemosensitization for controlling weeds in the field is a promising weed control measure for sustainable agriculture. The use of plant chemosensory substances to control pests is undoubtedly one of the development directions of plant protection. Chemosensory substances are the result of competition and natural selection of organisms in the ecosystem over a long period of time, and they are adapted to the ecosystem, so we should apply this ecological mechanism appropriately to avoid the harmful effects of chemosensory effects as much as possible, but utilize its positive effects as much as possible, so as to achieve the unity of the economic, social and ecological benefits, and to realize the sustainable development of agriculture. According to the estimation of the United States Department of Agriculture (USDA), the application of the new technology of chemosensitization will bring 2 billion dollars of economic benefits to the United States agriculture. Therefore, the application prospect of chemosensitization is quite considerable.In the world's second chemosensitization conference held in Canada in August 1999, there are a large number of paper reports involving chemosensitizers as insecticides, fungicides, herbicides and plant growth regulators in the development of agricultural application prospects, thus for more effective control of pests and diseases, protection of the ecological environment, and to improve the economic benefits, providing a brand-new development space. Isolation, extraction and identification of new chemosensory substances is an important direction of chemosensitization research. However, few of the identified chemosensory substances have application value. Therefore, in future research, we should focus on the combination of indoor research on chemosensitization and field application, identify new chemosensory substances and explore their potential for weed control, and develop non-polluting herbicides on this basis, which will have a great impact on the sustainable development of agriculture. In addition, the research on the production, release and mechanism of action of chemosensory substances is still a weak link and needs to be further explored. As our understanding of the selection mechanism, mechanism of action, and gene regulation of biosynthesis of chemosensory substances increases, it will be possible to successfully utilize existing germplasm resources to increase the production of these chemicals and to regulate the rate of release of chemosensory substances from growing or residual plants for seasonal weed control. This area of technology, although complex, shows new promise for integrated weed control. Chemical sensing is a research field involving multiple disciplines, so it is necessary to introduce multidisciplinary ideas and methods, and researchers from different disciplines*** participate and cooperate with each other to make this emerging cross-discipline mature, to better utilize its potential application value, and to propose reasonable measures with ecological safety, so as to provide new countermeasures for the sustained development of agriculture in China.