Treating plants with chitin and its derivatives before plant susceptibility can produce a sensitizing effect, and the treated plants can show a higher preventive effect than normal plants when they are infected by pests and diseases. It can be toxic to certain fungi, bacteria, viruses and pests, and induce plants to activate their defense systems.
Chitooligosaccharides cannot directly inactivate viruses, but have obvious inhibitory effects on the replication and long-distance movement of viruses in plants. By inhibiting the transmission of viruses and viroids between plants, the host ’s allergic reaction to infection is increased to achieve control. The effect of plant viral diseases. Used before the virus occurs, it can prevent the occurrence of viral diseases, can induce plant resistance to virus proliferation and long-distance movement in the body, and its induction activity does not depend on the host R gene. Used after a virus outbreak, it can inhibit the spread of the virus to the new leaves . It has a broad spectrum of fungal effects and has varying degrees of preventive effects on almost all fungal diseases, including powdery mildew, downy mildew, black nevus, and bacterial wilt, etc., mixed with targeted fungicides, such as enoyl Morpholine, flusilazole, pyraclostrobin, thiofuramide, elicin, tebuconazole, cyanfenapyr, etc., can achieve both internal and external considerations to achieve the effect of reducing drugs and increasing efficiency.
Chitin, as the main component of the cell wall of fungal pathogens, can stimulate plants to produce an immune response. There are multiple pattern recognition receptors on the cell membrane of plants. By identifying some common and conserved molecular motifs on pathogens (that is, pathogen-related molecular patterns), innate immune responses are triggered. The innate immunity of plants is the immune system of plants An important part of. Chitooligosaccharides can bind to receptors on plant cells to stimulate the production of resistance signal molecules. After signal transduction, they can stimulate the expression of resistance genes and produce resistance substances, so as to achieve the purpose of preventing and controlling diseases.
Generally, the degree of polymerization of chitooligosaccharides is from 2 to 10, and the distribution of acetyl groups on the chitosan molecular chain is random, and its number and position have a great influence on the activity of chitooligosaccharides. Chitosan oligosaccharides vary greatly in the degree of deacetylation in the deacetylation process, that is, under the same conditions, the higher the degree of deacetylation, the more free radical content, the higher the chitosan bacteriostatic activity.
In the process of agricultural production, the rapid changes in the external environment will cause huge irreversible damage to plants. Low-temperature freezing damage often occurs in the greenhouses in the north and open field crops in early spring. When the weather is abnormal, freezing damage or cold damage will also occur in the citrus and grapes in the south. The absorptive capacity of the plant is reduced, and the photosynthetic efficiency is low, which directly affects crop yield and quality. For example, low temperature environment can easily reduce the fluidity and peroxidation of plant cell membranes, causing damage to plant cells. Chitooligosaccharides can increase the content of cold-resistant substances such as soluble proteins and soluble sugars, reduce the level of peroxidation of membrane lipids and increase the permeability of membranes Degree, maintain a higher photosynthetic intensity of the crop, and effectively resist the damage of low temperature to the crop. The Miura Baicao Zhang Jianbo test showed that chitosan oligosaccharide has a significant effect in inducing cold resistance of plants, and the effect is significant when used 1 to 7 days in advance. In addition, through the spinach test under high temperature environment, Zhang Jianbo found that the spinach leaves sprayed with 500 times of Baijing (3% aminooligosaccharin) were damaged much less than the control, indicating that the chitosan oligosaccharides were resistant to heat, The effect of heat resistance is obvious, and the heat resistance of chitooligosaccharides is of great significance for the use of chitooligosaccharides in high temperature seasons.
After the chitosan oligosaccharide is absorbed by the plant, it induces the plant to produce indoleacetic acid and other auxins and gibberellin, which stimulates the root development of the plant. In the pepper, rice, and potato seeds, it is mixed with 300-500 times liquid 100% , It can stimulate the early germination of crops, and the capillary roots are many and long at the seedling stage of the crops. In the middle and late stages, the potatoes have strong absorption root systems, make better use of fertilizers and water, and become the basis of drought resistance and yield increase. Treating cotton seed coating with 0.05 ~ 0.2% concentration for 30min can stimulate seed germination, increase germination rate and increase the number of bolls per plant.
Chitooligosaccharides have antibacterial effects in plant cells and tissues, induce plant production of chitinase, and can increase enzyme activity, promote protein synthesis, regulate plant gene closure and opening, and induce auxin indoleacetic acid (IAA) synthesis . It stimulates a variety of plant growth and development genes, synthesizes biologically active substances that are beneficial to plant growth, activates plant cells, and promotes rapid plant growth and development.After treatment of plant seeds with chitooligosaccharides, it promotes neat and consistent emergence, thick main stems, promotes early sealing of ridges, promotes the early growth of plants, shortens the time of vegetative growth, and can bloom 2 to 3 days in advance, laying a foundation for increasing yield The harvest period can also be 3 to 5 days ahead of the blank control. The experiment found that the treatment of cucumber seeds and seedlings with low concentration of chitosan (optimum concentration 0.1 mg · L-1) can promote the growth of cucumber seedlings. Compared with the control group, all growth indexes are significantly increased.
Chitooligosaccharides can induce and increase the activity of P450 enzymes in plant cells and degrade chemical pesticide residues in plants. For tea, Chinese medicinal materials, fruits and vegetables, tobacco and other crops of cypermethrin, cypermethrin, pyridaben, biphenyl The degradation effect of pyrethrin is remarkable, reaching 100%.
When mixed with fungicides, the amount of fungicides can be greatly reduced, and the maximum amount of chemical pesticides can be reduced by 90%. The effect of preventing crop diseases and increasing yield is obvious. In addition, chitosan and its derivatives can be encapsulated with Trichoderma, Beauveria bassiana, Bacillus thuringiensis and other biological bacteria to make a preparation, which is not only conducive to the storage and transportation of these microbial preparations (as a carbon and nitrogen source of microorganisms) Can also promote their use effect.
The loss of fruits and vegetables after picking is mainly caused by fungal infections, physiological diseases and physical injuries. The preservation of fruits and vegetables is based on controlling the activities of microorganisms to slow down their normal life activities, and to maintain the natural storage and disease resistance of fruits and vegetables, that is, to inhibit the respiration of fruits and vegetables, prevent ethylene production or reduce ethylene concentration.
Use chitosan and its derivatives as the main aqueous solution or emulsion, spray or soak on the surface of fruits and vegetables. After drying, it can form a colorless transparent film, reduce the transpiration of fruits and vegetables, and maintain a good texture for fruits and vegetables. Solutions with different concentrations have different viscosities, and the degree of density of the fresh-keeping film formed is also different, which has a significant effect on the length of fresh-keeping time. Generally, a concentration of 1% ~ 2% is ideal.
(1) Seed treatment
100ppm seed soaking for 12 ~ 24 hours (depending on temperature), or 500ppm seed dressing or spraying;
(2) Foliar spray
50 ~ 100 ppm (manual or mechanical sprayer); suitable for flight prevention, the concentration needs to be increased;
(3) Underground punching
The dosage per mu is 15 ~ 25 grams of chitosan oligosaccharide drug;