1. Agricultural application 1. Rapid propagation through tissue culture is the most potential application in production, including ornamental flowers, vegetables, fruit trees, field crops and other cash crops. Rapid propagation technology is not limited by seasons and other conditions, and its growth cycle is short, which can propagate plants that cannot or are difficult to reproduce. Rapid propagation can be carried out in the following ways: (1) a large number of axillary buds are produced through shoot tips, stem segments and bulb discs; ⑵ Adventitious buds are directly induced by roots, leaves and other organs; ⑶ Callus culture induced adventitious buds. In vitro rapid propagation is used for the following production or research: (1) the propagation of a small number of hybrids obtained in cross breeding and the preservation of inbred lines and sterile lines. (2) Propagation of a few virus-free seedlings obtained by virus-free culture. (3) Breeding and producing seedlings that are in urgent need or have fewer provenances. Due to the characteristics of short tissue culture cycle, high proliferation rate and year-round production, as well as the miniaturization of culture materials and test-tube seedlings, a large number of plants can be cultivated in a limited space and a large number of seedlings can be cultivated in a short time. 2. During the growth process, almost all the virus-free plants have virus diseases to varying degrees, and some varieties even have several virus diseases at the same time. In particular, many horticultural plants reproduce by asexual reproduction. If they suffer from viral diseases, they will be infected more and more, and even have extremely serious consequences. Since 1952 Morel found that virus-free seedlings could be obtained by micro-shoot tip culture, micro-shoot tip culture has become one of the important ways to solve the harm of virus diseases. If combined with heat treatment, the effect of virus-free culture can be improved. For woody plants, it is difficult for plants obtained by shoot tip culture to grow roots, so virus-free seedlings can be cultivated by shoot tip micro-grafting. Tissue culture of virus-free seedlings has been applied to the routine production of many crops. Such as potatoes, sweet potatoes, strawberries, apples, carnations, chrysanthemums and so on. In addition, virus-free seedling production centers have been established in many areas, and standardized systematic procedures for virus-free seedling cultivation, identification, propagation, preservation, utilization and research have been formed, thus achieving the purpose of maintaining excellent germplasm and economic characteristics of horticultural plants. 3. The application of plant tissue culture technology in breeding provides many means and methods for breeding, which makes the breeding work more effective under new conditions. (1) ploidy breeding shortens the breeding cycle and has obvious heterosis. (2) overcoming the incompatibility and sterility of distant hybridization (embryo culture) (3) preserving germplasm, such as: cultivating haploid plants with anthers; Somatic hybridization and gene transfer with protoplasts; Ovary, embryo and ovule are used to complete the in vitro development and fertilization of embryos and the preservation of germplasm resources. Embryo culture technology has been used for a long time. In the case of distant hybridization between species, hybrid embryos often stop developing due to physiological and metabolic reasons, so hybrid plants cannot be obtained. Therefore, embryo culture can ensure the smooth progress of distant hybridization. In the 1950s, it was more applied in practice. Such as peach, orange, kidney bean, pumpkin, lily, iris, etc. "Bailan" is a distant hybrid of Chinese cabbage × Chinese cabbage, which is obtained by hybrid embryo culture. Ovule and ovary culture can also be used to achieve success for species whose early embryos are too small to be cultured. In vitro fertilization can also be carried out by ovule and ovary culture to overcome the obstacles of stigma or style to fertilization, so that pollen tubes can directly enter the ovule for fertilization. Haploid plants have been obtained from anther and pollen culture in about 20 horticultural plants, such as apples, oranges, grapes, strawberries, asparagus, sweet peppers, cabbages and geraniums. Conventional breeding needs multiple generations of self-crossing to obtain pure line materials, while haploid breeding can quickly obtain homozygous diploids after chromosome doubling, which greatly shortens the generation and years of breeding. Mutants can be screened by tissue culture. The occurrence of mutation varies from place to place, and the inheritance of shoot tip is relatively stable, while the variation rate of root, stem, leaf, callus and cell culture is relatively large. Hormones in the culture medium can also induce variation, and variation varies with concentration. In addition, ultraviolet rays, X rays and gamma rays can be used to irradiate materials to induce mutations. In tissue culture, there are many polyploids and mixed ploidys, which provide materials for breeding and can be screened according to needs. It is more effective to screen mutants at the cell level by tissue culture and techniques similar to microbial screening. The development of protoplast culture and somatic hybridization technology shows a brand-new prospect for breeding. Many plants are regenerated by protoplast culture, and some plants have obtained somatic hybrids, which has important theoretical and practical value. With the deepening and improvement of this work, protoplast culture will have a far-reaching impact on breeding. 4. Factory Propagation In recent years, the factory production of tissue culture seedlings has flourished in the field of horticultural plant production as a new technology and production means. ⑴ Meaning: It refers to the method of inoculating explants on artificially prepared culture medium on the basis of plant tissue culture, and dedifferentiating and redifferentiating cells into new tissues and organs by controlling environmental conditions, thus cultivating a group of seedlings like mother plants. For example, the industrial production of tissue culture and seedling raising of African violets. ⑵ Features: rapid propagation, uniformity, no pests and diseases, short cycle, perennial production and stable characters. ⑶ Function: It is beneficial to the low propagation coefficient, the rapid propagation of heterozygote materials, the propagation of easily separated materials with good sexual reproduction, and the maintenance of excellent heritability of phenotypic plants selected from heterozygote recombinant inbred lines. The production of non-toxic tissue culture seedlings can also reduce the spread of diseases. It can reduce the influence of climatic conditions on seedling reproduction and alleviate the contradiction between supply and demand in light season. (4) Present situation: The rapid development of tissue culture technology of horticultural plants in some advanced countries in the world began in the 1960s. With the gradual deepening of the exploration of the growth and differentiation law, by the 1970s, the flower industry alone had established large-scale commercial production of test-tube seedlings in the production of more than 20 kinds of flower seedlings, such as orchids, lilies, gerbera, Erythrina, chrysanthemums, carnations and Petunia. By 1984, the total output value of the world flower and seedling industry has reached 2 billion US dollars, of which the total market value of American flower and seedling exceeds 600 million US dollars, and 60% of the seedlings of Japan Sanyou Seedling Company are propagated by tissue culture technology. 1985 has only one orchid, and there are more than 100 companies registered in the United States, with annual sales exceeding 1 100 million dollars. Due to the application of tissue culture technology, the promotion of new flower varieties has been accelerated. In the past, it took several years or even more than ten years to popularize a new variety by conventional methods, but now it can be popularized and applied worldwide as long as 1 ~ 2 years. The adoption of rapid propagation technology in China has also enabled the rapid popularization and application of fine varieties. For example, the application of Guangdong cut chrysanthemum "Huang Xiufeng" has made chrysanthemum bigger, stronger in growth, brighter in color and stronger in disease resistance, opened up a channel to enter the Hong Kong market, made the promotion of more than 30 foliage plants spread all over the country quickly, enriched people's lives, domesticated hundreds of wild species of Chrysopa in nature, cultivated a number of vertical greening materials for gardens, and promoted the development of the garden industry. 5] Constraints: There are also some difficulties in plant tissue culture. The first is the contradiction between reproduction efficiency and commodity demand. Some crops can't meet the needs of production because the propagation method has not been solved. Secondly, how to reduce the occurrence of mutation in the culture process. More importantly, the cost of factory production of tissue culture seedlings should be reduced. Only by reducing the cost can we put it into production and application better. In short, with the development of tissue culture technology and the wide application of various culture methods, this technology has shown great potential in genetic breeding and variety breeding, especially after the implementation of bioengineering and factory seedling raising, it will play an important role in the technological revolution as a new industry. The second is the application in genetics, molecular biology, cell biology, histology, embryology, genetic engineering, bioengineering and so on. Uncovering the secrets of life activities requires the cooperation of many kinds of science and technology, among which plant tissue culture technology is indispensable, which provides an effective and rapid method for genetics, molecular biology, cell biology and bioengineering. Because to reveal the mystery of life, we must first study the function of a single gene, how it is assembled in cells, how it is related to other genes, and how it is expressed and regulated. Isolate a single gene, sequence its DNA, and then mutate some of its bases. Then, we need to send the gene to the recipient cell and observe its expression to determine its function. In order to produce regenerated plants, it is necessary to cultivate recipient cells that receive genes in tissues. 3. Using tissue culture materials as plant bioreactors Chinese herbal medicine is a precious wealth of human beings, but many kinds of Chinese herbal medicine resources are scarce, the output is insufficient, and even on the verge of extinction. If it can be produced by tissue and cell culture in the laboratory, it can not only solve the existing difficulties, but also improve its medicinal value by screening cell lines with high yield of effective components. For example, the production of ginsenoside by culturing ginseng suspension cells has formed a scale in Japan and other countries. Protein, amino acids, antibiotics and vaccines can also be produced by using cultured plant cells and tissue cells as bioreactors. For example, the experiment of producing hepatitis B vaccine with raw vegetables is under way. 4. Research on other unknown sciences Modern science has developed very rapidly. Many unexpected things may happen now, and new inventions, discoveries and creations emerge one after another. What is considered impossible today may become a reality tomorrow. Plant tissue culture also has many untapped potentials. Maybe one day people will plant giant pumpkins in triangular bottles. In short, the current plant tissue culture is still in the development stage, far from reaching its peak, many mechanisms have not been clarified, and its potential is far from being brought into play. I believe that in the next few decades, organizational training will have greater development in China, and will play a greater role in agriculture, pharmaceutical industry, processing industry and so on, creating greater economic benefits.