A drought-resistant and saline-alkali-tolerant corn seed coating agent and its preparation method

Abstract

The present invention relates to the technical field of seed coating agents, and particularly relates to a drought-resistant and saline-alkali-tolerant corn seed coating agent and a preparation method thereof, comprising the following raw materials: nano-polyacrylamide, polyvinyl alcohol, Mo@ZIF-8, modified MgAl-LDH, gibberellin, proline, citric acid, sodium carboxymethyl cellulose, and Bacillus subtilis. In the present invention, Mo@ZIF-8 and modified MgAl-LDH synergistically enhance the drought resistance and saline-alkali tolerance of corn seeds. Mo@ZIF-8 adsorbs Na + to prevent it from entering the seed epidermal cells, alleviating saline-alkali stress. Modified MgAl-LDH forms a hydration layer with water molecules to effectively retain water. The surface-grafted polydopamine helps to achieve dynamic water regulation, enhancing the drought resistance of corn seeds. The catalytic activity of Mo@ZIF-8 is enhanced through the photothermal effect, promoting the oxidation of Cl ‑ to release Cl2. The gradually released imidazole molecules from Mo@ZIF-8 reduce the alkalinity of the rhizosphere environment, improve the seed germination environment, optimize the rhizosphere microbial environment, and promote crop root growth.

Description

Technical Field

[0001] The present invention relates to the technical field of seed coating agents, and specifically relates to a drought-resistant and saline-alkali-tolerant corn seed coating agent and a preparation method thereof. Background Art

[0002] Corn is one of the most important food crops globally, and its yield directly affects agricultural economy and food security. However, global climate change and unreasonable farming methods have led to the gradual degradation of arable land, and drought and saline-alkali stress have become the main environmental factors affecting corn yield. In a drought environment, the soil moisture is severely insufficient, and the water absorption of seeds is limited, resulting in a reduced germination rate and difficulty in seedling emergence. In addition, saline-alkali stress also hinders seed germination through osmotic stress and ion toxicity, and even causes plant death. Seed coating agents are preparations with film-forming properties used for pre-sowing treatment of seeds. Traditional seed coating agents are mainly used to improve the sowing adaptability of seeds and prevent and control diseases, and usually contain ingredients such as pesticides, fungicides, thickeners, and trace elements. There are still deficiencies in enhancing the drought resistance and saline-alkali tolerance of seeds. Traditional seed coating agents cannot effectively adsorb and retain soil moisture, have poor water retention performance, are difficult to maintain the water environment required for seed germination under drought conditions, and cannot effectively alleviate salt damage. Seed germination and seedling growth are still inhibited. In addition, traditional seed coating agents have a single function, mainly focusing on disease prevention and control, and do not fully consider enhancing the adaptability of seeds to adversity. In recent years, the application of nanotechnology in the agricultural field has become increasingly widespread. Due to their ultra-high specific surface area, slow-release ability, and multifunctionality, nanomaterials can effectively improve the stress resistance of seeds, not only improving the seed germination environment, promoting early growth, but also enhancing the survival rate of plants under adversity, providing a more reliable guarantee for corn planting. Therefore, developing a nano seed coating agent that can enhance the drought resistance and saline-alkali tolerance of seeds and simultaneously has a growth-promoting function is of great significance for high and stable yield of corn. Summary of the Invention

[0003] (1) Technical Problems to be Solved

[0004] The purpose of the present invention is to provide a drought-resistant and saline-alkali-tolerant corn seed coating agent and a preparation method thereof. By optimizing the formula of the corn seed coating agent and combining modern nanotechnology, the drought resistance of corn seeds is significantly improved, the water absorption and germination of seeds in a drought environment are ensured, the saline-alkali tolerance of seeds is enhanced, the inhibition of seed germination by saline-alkali stress is reduced, the seed germination rate is increased, seedling growth is promoted, stress resistance is enhanced, and effective guarantee is provided for the stable growth and high yield of corn in a drought and saline-alkali stress environment.

[0005] (2) Technical Solutions

[0006] To achieve the above object, on the one hand, the present invention provides a drought-resistant and saline-alkali-tolerant corn seed coating agent, which comprises the following raw materials in parts by weight: 10-20 parts of nano-polyacrylamide, 5-10 parts of polyvinyl alcohol, 15-25 parts of modified magnesium-aluminum layered double hydroxide (modified MgAl-LDH), 0.2-1 part of gibberellin, 0.1-0.5 part of proline, 1-3 parts of citric acid, 10-20 parts of sodium carboxymethylcellulose, 6-10 parts of Bacillus subtilis, and 50-60 parts of purified water;

[0007] The drought-resistant and saline-alkali-tolerant corn seed coating agent further comprises:

[0008] Mo@ZIF-8;

[0009] The weight ratio of Mo@ZIF-8 to modified MgAl-LDH is 5:(15-25);

[0010] The nano size of the Mo@ZIF-8 is 85-125 nm, and the specific surface area is 1300-1400 m 2 / g.

[0011] Furthermore, the preparation method of the Mo@ZIF-8 comprises:

[0012] S11. Dissolve zinc nitrate in methanol under nitrogen protection and stirring to obtain a zinc nitrate solution. Then dissolve 2-methylimidazole and ammonium molybdate in methanol and stir for 1-2 h, and then slowly add the zinc nitrate solution while raising the temperature to 35-45 °C. Continue to stir and react for 24-26 h, and control the pH value to 10.5-11 with ammonia water. Let it stand for 15-18 h to obtain a first mixed solution;

[0013] S12. Centrifuge the first mixed solution at a high speed at a rotation speed of 8000-10000 rpm for 10-15 min. Wash the separated solid alternately with methanol and purified water 3 times and then perform vacuum drying. The drying temperature is 135-145 °C, and after drying for 6-8 h, obtain Mo@ZIF-8 and grind it into a powder for standby.

[0014] Furthermore, the molar ratio of zinc nitrate, 2-methylimidazole, and ammonium molybdate is 1:(8-10):(0.02-0.04).

[0015] Furthermore, the preparation method of the modified MgAl-LDH comprises:

[0016] S21. Dissolve magnesium nitrate and aluminum nitrate in purified water under stirring, control the molar ratio of Mg 2+ and Al 3+ to be 3:1, and prepare a 0.2 mol / L metal ion mixed solution;

[0017] S22. Slowly add 1 mol / L sodium hydroxide solution to the metal ion mixed solution under nitrogen protection and stirring until the pH value rises to 9.5-10.5, and raise the temperature to 65-75°C, continue stirring and reacting for 4-6 hours, and then stand for 12-15 hours to obtain a second mixed solution;

[0018] S23. The second mixed solution was separated by vacuum filtration, and the separated precipitate was washed three times with purified water and then vacuum dried at a drying temperature of 55 to 65 ° C. After drying for 12 to 15 hours, MgAl-LDH was obtained and ground into a powder for later use;

[0019] S24. Dissolve dopamine hydrochloride in phosphate buffered saline under nitrogen protection and stirring, slowly add MgAl-LDH powder after stirring for 0.5-1h, raise the temperature to 35-45°C, and control the pH value to 8.5-9 with 0.1 mol / L sodium hydroxide solution, continue stirring for 14-16h to obtain a third mixed solution;

[0020] S25. The third mixed solution is subjected to high-speed centrifugation at a speed of 8000-10000 rpm for 10-15 min. The separated solid is washed three times with purified water and then vacuum dried at a drying temperature of 65-75° C. After drying for 12-15 h, the modified MgAl-LDH is obtained and ground into powder for later use.

[0021] Furthermore, the nanometer size of the modified MgAl-LDH is 100-120 nm, and the specific surface area is 120-150 m 2 / g.

[0022] Furthermore, the mass ratio of the MgAl-LDH to dopamine hydrochloride is 1:(0.1-0.3).

[0023] On the other hand, based on the same inventive concept, the present invention also provides a method for preparing a drought-resistant and salt-alkali-tolerant corn seed coating agent, which is applied to the drought-resistant and salt-alkali-tolerant corn seed coating agent, comprising the following steps:

[0024] S31. Add polyvinyl alcohol to purified water in a container and stir well, while heating to 75~85°C, stirring for 1~2h and then cooling to 30~40°C, then adding sodium carboxymethyl cellulose and stirring for 1~2h, controlling the stirring speed to 300~400 rpm, cooling to room temperature, and stirring at room temperature for 0.5~1h to obtain a fourth mixed solution;

[0025] S32. While stirring, successively add nano-polyacrylamide, Mo@ZIF-8 and modified MgAl-LDH into the fourth mixed solution and stir well. The stirring speed is 400 - 600 rpm, the stirring temperature is 45 - 55 °C. After stirring for 0.5 - 1 h, perform ultrasonic treatment. The ultrasonic frequency is 40 - 50 kHz. After ultrasonic treatment for 0.5 - 1 h, obtain the fifth mixed solution;

[0026] S33. While stirring, continue to add proline and citric acid into the fifth mixed solution and stir for 0.5 - 1 h. At the same time, use phosphate buffered saline to control the pH value to be 6.5 - 7.5. Subsequently, continue to add gibberellin and continue to stir for 0.5 - 1 h to obtain the sixth mixed solution;

[0027] S34. While stirring at a low speed, slowly add Bacillus subtilis liquid into the sixth mixed solution, control the stirring speed at 200 - 250 rpm, and continue to stir at room temperature for 10 - 20 min, then filter through a 0.22 μm filter membrane to obtain the drought-resistant and salt-tolerant corn seed coating agent.

[0028] Furthermore, the usage method of the drought-resistant and salt-tolerant corn seed coating agent is as follows: Take corn seeds, coat them according to the ratio of 1 kg of corn seeds : 20 - 30 mL of seed coating agent, use a drum-type seed coating machine, and uniformly coat at a rotation speed of 50 - 100 rpm. Subsequently, place the coated seeds in a ventilated environment and air-dry until the surface is dry and does not stick to the hand.

[0029] The action mechanisms of the above raw material components are as follows:

[0030] Nanoscale polyacrylamide is a high molecular polymer with super water absorption and water retention capabilities. It can absorb hundreds of times its own mass of water through a nanoscale three-dimensional network structure, form a hydrogel film on the seed surface, reduce the water evaporation rate, maintain a moist environment around the seed, ensure the water absorption requirements of the seed under drought conditions, increase the emergence rate, and can also adsorb and slowly release water-soluble nutrients, maintain the nutrient supply required for seed germination and early seedling growth, and increase the germination rate of corn seeds. Polyvinyl alcohol is a water-soluble polymer material with good film-forming and adhesion properties. It can form a hydrophilic film on the seed surface, protect the seed from the influence of the external adverse environment, extend the action time of active substances, and at the same time enhance the binding force between the seed coating agent and the seed, ensure that other active ingredients are firmly coated, and prevent shedding. Gibberellin is a plant growth regulator that can promote cell division, elongation, and seed germination, while enhancing salt tolerance, improving root growth, increasing water and nutrient absorption, alleviating the inhibitory effect of saline-alkali stress on seedlings, and improving seedling growth. Proline is a natural amino acid with osmotic regulation and antioxidant functions. It can improve the tolerance of plant cells to adverse environments such as drought and salinity. It can balance the osmotic pressure inside and outside the cell, reduce water loss, protect the cell membrane structure, maintain cell activity, protect seeds and seedlings from osmotic stress damage, and at the same time scavenge reactive oxygen species generated by saline-alkali stress, reduce oxidative damage, and enhance plant stress resistance. Citric acid is a natural organic acid that can chelate salt ions such as , in the soil, reduce their toxicity to seeds and seedlings, alleviate saline-alkali stress, and at the same time play a role in improving the root environment of crops. It can adjust the soil pH value, promote the reproduction of rhizosphere microorganisms, release trace elements, enhance the early nutrient supply of seeds, and enhance the absorption capacity of corn seeds for nutrients and water. Sodium carboxymethyl cellulose is a natural polymer binder with dual functions of water absorption, moisture retention and slow release. It can enhance the adhesion between the seed coating agent and the seed, prevent the loss of active ingredients, and at the same time adsorb moisture in the environment, maintain the moisture around the seed, help the seed germinate, and can also slowly release active substances and extend the action time of the seed coating agent. Bacillus subtilis is a probiotic microorganism that can secrete bioactive substances such as organic acids and extracellular polymers, improve the soil environment, inhibit harmful bacterial populations, enhance the disease resistance of seeds and seedlings, and increase the field seedling emergence rate.

[0031] In the drought-resistant and saline-alkali-tolerant corn seed coating agent, Mo@ZIF-8 and modified MgAl-LDH synergistically enhance the drought resistance and saline-alkali tolerance of corn seeds. Mo@ZIF-8 is a metal-organic framework material prepared by loading molybdenum nanoparticles on the surface of ZIF-8. It has a highly ordered nanoscale pore structure, and its pore size (about 3.4 Å) is suitable for selectively screening small ions. In the soil environment, Mo@ZIF-8 has a strong adsorption capacity for Na + while for With lower selectivity, Mo@ZIF-8 preferentially adsorbs Na + , thus reducing from entering the epidermal cells of corn seeds, alleviating saline-alkali stress, and simultaneously maintaining concentration, making the / ratio increase. A high / ratio helps maintain cell osmotic pressure, prevent water loss, reduce dehydration caused by salt stress, and also helps maintain enzyme activity, maintain protein synthesis and energy metabolism within the cell, and promote seed growth. Magnesium-aluminum layered double hydroxide (MgAl-LDH) is a layered nanomaterial with ion-exchange and slow-release properties, consisting of positively charged Mg 2+ and Al 3+ lamellae, as well as exchangeable anions such as OH - , NO 3 - , PO 4 3- sandwiched between the layers. Modified MgAl-LDH obtained by grafting polydopamine on its surface can effectively alleviate saline-alkali stress and promote water retention. In an arid environment, the -OH between the layers of modified MgAl-LDH forms a stable hydration layer with water molecules through physical adsorption and chemical bonding, effectively retaining water and maintaining a locally humid environment around corn seeds. The polydopamine grafted on the surface of modified MgAl-LDH helps achieve dynamic water regulation. During the day when the light is strong, polydopamine absorbs solar energy and converts it into local heat energy, raising the temperature around the seeds, prompting the release of bound water between the layers of modified MgAl-LDH, effectively supplementing the water required for the growth of corn seeds; when the temperature drops at night, polydopamine reduces the photothermal effect, and the -OH between the layers of modified MgAl-LDH can re-adsorb water in the air, forming a dynamic water recovery system, enhancing the water retention capacity of the environment around the seeds, thereby enhancing the drought resistance of corn seeds and promoting seed germination and root extension. At the same time, polydopamine enhances the catalytic activity of Mo nanoparticles in Mo@ZIF-8 through the photothermal effect, promoting the oxidation of Cl - to Cl 2 release, enhancing the conversion efficiency of Cl - , and effectively reducing the toxicity of Cl - to corn seeds in a saline-alkali environment. At the same time, modified MgAl-LDH can also slowly release nutrients such as Mg 2+ , Al 3+ , NO 3 - , PO 4 3- required for crop growth, and through ion exchange, it competes with in the soil for adsorption, effectively inhibiting accumulation, reduce its toxicity to the cell membrane and metabolic enzyme activity of corn seeds, and enhance the saline-alkali tolerance of corn seeds. In addition, the pH value of saline-alkali soil is usually relatively high, above 8.5, which makes Mg 2+ 、Al 3+ 、NO 3 - 、PO 4 3- and other nutrients form insoluble compounds under alkaline conditions, reducing the availability of nutrients, affecting cell physiological metabolism, inhibiting root development, and also affecting the rhizosphere microbial community, reducing the activity of plant growth-promoting rhizobacteria, thus affecting crop health. However, in the high pH environment of saline-alkali soil, the framework structure of Mo@ZIF-8 will gradually dissociate and slowly release Mo 6+ 、Zn 2+ and imidazole molecules. Mo 6+ is a cofactor of nitrate reductase, which can improve the nitrogen utilization rate of corn seeds, help crop seedlings maintain nitrogen metabolism homeostasis in saline-alkali environments, supply crops to synthesize amino acids, and enhance crop stress resistance; Zn 2+ is an essential element for chlorophyll synthesis, which can ensure that corn seeds can still efficiently synthesize organic matter in adverse environments, and enhance the growth power of corn in adversity; and imidazole molecules are amphoteric molecules, which will absorb under high pH conditions, reduce the alkalinity of the rhizosphere environment, improve the seed germination environment, and at the same time improve nutrient absorption, optimize the rhizosphere microbial environment, and promote crop root growth. In short, Mo@ZIF-8 and modified MgAl-LDH synergistically improve the drought resistance and saline-alkali tolerance of corn seeds, increase the seed germination rate, promote seedling growth, enhance stress resistance, and provide effective guarantees for the stable growth and high yield of corn in drought and saline-alkali stress environments.

[0032] (3)Beneficial effects

[0033] Compared with the prior art, the beneficial effects of the present invention are:

[0034] 1. Mo@ZIF-8 and modified MgAl-LDH synergistically improve the drought resistance and saline-alkali tolerance of corn seeds. Mo@ZIF-8 preferentially adsorbs , reduce from entering the epidermal cells of corn seeds, relieve saline-alkali stress, maintain concentration, so that the / ratio increases, maintain cell osmotic pressure, maintain intracellular protein synthesis and energy metabolism, and promote seed growth;

[0035] 2. The -OH groups between the layers of modified MgAl-LDH form a stable hydration layer with water molecules through physical adsorption and chemical bonding, effectively retaining moisture and maintaining a locally humid environment around the corn seeds. The polydopamine grafted on its surface helps achieve dynamic moisture regulation and enhance the drought resistance of corn seeds;

[0036] 3. The polydopamine on the surface of modified MgAl-LDH enhances the catalytic activity of Mo nanoparticles in Mo@ZIF-8 through the photothermal effect, promoting the oxidation of Cl - to Cl 2 release, enhancing the conversion efficiency of Cl - and effectively reducing the toxicity of Cl - to corn seeds in saline-alkali environments;

[0037] 4. Modified MgAl-LDH slowly releases nutrients such as Mg 2+ , Al 3+ , NO 3 - , PO 4 3- required for crop growth. Through ion exchange, it competitively adsorbs with in the soil to inhibit its accumulation and enhance the saline-alkali tolerance of corn seeds;

[0038] 5. Mo@ZIF-8 gradually and slowly releases Mo 6+ , Zn 2+ and imidazole molecules in saline-alkali soil. Mo 6+ helps crop seedlings maintain nitrogen metabolism homeostasis, Zn 2+ enhances the growth power of corn, and imidazole molecules reduce the alkalinity of the rhizosphere environment, improve the seed germination environment, optimize the rhizosphere microbial environment, and promote crop root growth. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 FIG. 1 is the SEM image of Mo@ZIF-8 in Example 1 of the present invention;

[0040] Figure 2 FIG. 2 is the SEM image of modified MgAl-LDH in Example 1 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0041] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0042] The test equipment and preparations for the following examples are as follows: electronic balance (Sartorius, Germany), electrothermal constant temperature water bath (Kedao, Jiangsu), magnetic stirrer (Meiyingpu, Shanghai), high-speed centrifuge (Jidi, Guangzhou), vacuum drying oven (Jiecheng, Shanghai), ultrasonic instrument (Yixin, Shanghai), scanning electron microscope (Zeiss, Germany), specific surface area analyzer (Beijing Beishide Instrument Technology), seed coating machine (Sanli Grain, Shijiazhuang), handheld chlorophyll SPAD meter (Kruide, Qingdao), leaf area measuring instrument (Laiyin, Shandong); chemical drugs and reagents were purchased from Sigma-Aldrich.

[0043] Example 1: This example discloses a drought-resistant and salt-tolerant corn seed coating agent, which includes the following raw materials in parts by weight: 15 parts of nano-polyacrylamide, 7.5 parts of polyvinyl alcohol, 20 parts of modified MgAl-LDH, 0.6 parts of gibberellin, 0.3 parts of proline, 2 parts of citric acid, 15 parts of sodium carboxymethylcellulose, 8 parts of Bacillus subtilis, and 55 parts of purified water. The drought-resistant and salt-tolerant corn seed coating agent also includes Mo@ZIF-8, and the weight ratio of Mo@ZIF-8 to modified MgAl-LDH is 5:20. The nano-size of Mo@ZIF-8 is 90 nm, and the specific surface area is 1380 m 2 / g.

[0044] In the drought-resistant and salt-tolerant corn seed coating agent, Mo@ZIF-8 and modified MgAl-LDH synergistically improve the drought resistance and salt tolerance of corn seeds. Mo@ZIF-8 is a metal-organic framework material, which is prepared by loading molybdenum nanoparticles on the surface of ZIF-8. Figure 1 Figure + For the SEM image of Mo@ZIF-8, it can be seen that Mo@ZIF-8 has a highly ordered nano-scale pore structure, and its pore size is about 3.4 Å, which is suitable for selective screening of small ions. Therefore, in the soil environment, Mo@ZIF-8 can effectively screen and preferentially adsorb Na , thereby reducing from entering the epidermal cells of corn seeds and alleviating salt stress, while having lower selectivity for larger-radius . The strong adsorption of Mo@ZIF-8 on can effectively reduce the free concentration in the soil, enabling corn seeds to preferentially absorb , thereby maintaining a high / ratio within the cell. A high ratio is crucial for the osmotic regulation of cells. A high / The ratio helps maintain cell osmotic pressure, prevent water loss, reduce dehydration caused by salt stress, and also helps maintain enzyme activity, sustain protein synthesis and energy metabolism within the cell, enhance cell vitality, and promote seed growth. MgAl-LDH is a layered nanomaterial with ion-exchange and slow-release properties, consisting of positively charged Mg 2+ and Al 3+ lamellae, as well as exchangeable anions such as OH - , NO 3 - , PO 4 3- sandwiched between the layers. By grafting polydopamine onto its surface, modified MgAl-LDH can effectively alleviate saline-alkali stress and promote water retention. Figure 2 Figure Figure 2 shows the SEM image of modified MgAl-LDH. It can be seen that modified MgAl-LDH has an obvious layered structure. In a dry environment, the large number of nanoscale pores existing between the layers of modified MgAl-LDH have a strong capillary adsorption capacity for water molecules, can absorb moisture in the air, and the -OH between the layers of modified MgAl-LDH forms hydrogen bonds with water molecules, enhancing the ability to fix water molecules. That is, modified MgAl-LDH and water molecules form a stable hydration layer through physical adsorption and chemical bonding, effectively retaining water. This dual effect can effectively maintain a locally high-humidity environment around maize seeds. The grafting of polydopamine on the surface of modified MgAl-LDH helps achieve dynamic water regulation. Polydopamine is a chemical substance with excellent photothermal conversion and biocompatibility. When the sunlight is strong during the day, polydopamine absorbs solar energy and converts it into local heat energy, raising the temperature around the seeds, prompting the release of bound water between the layers of modified MgAl-LDH, effectively supplementing the water required for the growth of maize seeds. When the temperature drops at night, polydopamine reduces the photothermal effect, and the -OH between the layers of modified MgAl-LDH can re-adsorb moisture in the air and restore its hydrated state, forming a dynamic water recovery system, enhancing the water retention capacity of the environment around the seeds, thereby enhancing the drought resistance of maize seeds, ensuring that maize seeds can effectively absorb water under drought conditions, reducing water loss, improving water use efficiency, and promoting seed germination and root extension. At the same time, polydopamine enhances the oxidation catalytic activity of Mo nanoparticles in Mo@ZIF-8 through the photothermal effect, prompting the oxidation of Cl - in the soil and rhizosphere environment to volatile Cl 2 and releasing it, enhancing the conversion efficiency of Cl - , and effectively reducing the toxicity of Cl - to maize seeds in the saline-alkali environment. At the same time, modified MgAl-LDH can also slowly release Mg 2+ , Al 3+ , NO 3 - , PO4 3- nutrients required for crop growth such as, and through ion exchange with those in the soil carry out competitive adsorption to prevent from entering the epidermal cells of corn seeds, reducing accumulation on the cell membrane, alleviating its toxicity to the cell membrane and metabolic enzyme activity of corn seeds, and enhancing the saline-alkali resistance of corn seeds. In addition, the pH value of saline-alkali soil is usually relatively high, above 8.5, which makes Mg 2+ 、Al 3+ 、NO 3 - 、PO 4 3- and other nutrients easily form insoluble compounds under alkaline conditions, resulting in crops being unable to effectively absorb these essential nutrients for growth, reducing nutrient availability, affecting cell physiological metabolism, inhibiting root development, and also affecting the rhizosphere microbial community and reducing the activity of plant growth-promoting rhizobacteria in the rhizosphere, thereby affecting crop health. However, in the high pH environment of saline-alkali soil, the organic framework structure of Mo@ZIF-8 will gradually dissociate and slowly release Mo 6+ 、Zn 2+ and imidazole molecules. Mo 6+ is an important cofactor of nitrate reductase, which can improve the nitrogen utilization rate of corn seeds, help crop seedlings maintain nitrogen metabolism homeostasis in saline-alkali environments, supply crops to synthesize amino acids and proteins, help seedlings quickly adapt to adverse environments, and enhance stress resistance; Zn 2+ is an essential element for chlorophyll synthesis, which can ensure that corn seeds can still efficiently synthesize organic matter in adverse environments, enhancing the growth power of corn in adversity; and imidazole molecules are amphoteric molecules, which will absorb under high pH conditions, reduce the alkalinity of the rhizosphere environment, improve the seed germination environment, prevent nutrient solidification, enhance the biological availability of Mg 2+ 、Al 3+ 、NO 3 - 、PO 4 3- and other nutrients, optimize the rhizosphere microbial environment, and promote crop root growth. In summary, Mo@ZIF-8 and modified MgAl-LDH synergistically enhance the drought resistance and saline-alkali tolerance of corn seeds, improve the seed germination rate, promote seedling growth, enhance stress resistance, and provide effective guarantees for the stable growth and high yield of corn under drought and saline-alkali stress environments.

[0045] The preparation method of the Mo@ZIF-8 described above includes:

[0046] S11. Dissolve zinc nitrate in methanol under nitrogen protection and stirring to obtain a zinc nitrate solution. Then dissolve 2-methylimidazole and ammonium molybdate in methanol and stir for 1.5 h, and then slowly add the zinc nitrate solution while raising the temperature to 40 °C. Continue stirring and reacting for 25 h, and control the pH value to 10.8 with ammonia water. Let it stand for 16 h to obtain the first mixed solution;

[0047] S12. Centrifuge the first mixed solution at a high speed at 9000 rpm for 12 min. Wash the separated solid alternately with methanol and purified water for 3 times, and then perform vacuum drying at a drying temperature of 140 °C for 7 h to obtain Mo@ZIF-8 and grind it into a powder for standby.

[0048] The molar ratio of the zinc nitrate, 2-methylimidazole and ammonium molybdate is 1:9:0.03.

[0049] The preparation method of the modified MgAl-LDH includes:

[0050] S21. Dissolve magnesium nitrate and aluminum nitrate in purified water under stirring, control the molar ratio of Mg 2+ and Al 3+ to be 3:1, and prepare a 0.2 mol / L metal ion mixed solution;

[0051] S22. Slowly drop 1 mol / L sodium hydroxide solution into the metal ion mixed solution under nitrogen protection and stirring until the pH value rises to 10, while raising the temperature to 70 °C. Continue stirring and reacting for 5 h, and then let it stand for 14 h to obtain the second mixed solution;

[0052] S23. Filter the second mixed solution by vacuum filtration. Wash the separated precipitate with purified water for 3 times and then perform vacuum drying at a drying temperature of 60 °C for 14 h to obtain MgAl-LDH and grind it into a powder for standby;

[0053] S24. Dissolve dopamine hydrochloride in phosphate buffered saline under nitrogen protection and stirring. Stir for 0.8 h and then slowly add the MgAl-LDH powder while raising the temperature to 40 °C, and control the pH value to 8.8 with 0.1 mol / L sodium hydroxide solution. Continue stirring for 15 h to obtain the third mixed solution;

[0054] S25. Centrifuge the third mixed solution at a high speed at 9000 rpm for 12 min. Wash the separated solid with purified water for 3 times and then perform vacuum drying at a drying temperature of 70 °C for 14 h to obtain the modified MgAl-LDH and grind it into a powder for standby.

[0055] The nano-size of the modified MgAl-LDH is 105 nm, and the specific surface area is 145 m 2 / g.

[0056] The mass ratio of the MgAl-LDH to dopamine hydrochloride is 1:0.2.

[0057] A preparation method of a drought-resistant and saline-alkali-tolerant corn seed coating agent, which is applied to the drought-resistant and saline-alkali-tolerant corn seed coating agent, comprises the following steps:

[0058] S31. Add polyvinyl alcohol to purified water in a container and stir well, while heating to 75-85 °C. After stirring for 1-2 h, cool to 30-40 °C, then add sodium carboxymethylcellulose and continue to stir for 1-2 h. Control the stirring speed at 300-400 rpm. After cooling to room temperature, continue to stir at room temperature for 0.5-1 h to obtain a fourth mixed solution;

[0059] S32. Add nano-polyacrylamide, Mo@ZIF-8 and modified MgAl-LDH to the fourth mixed solution in sequence under stirring and stir evenly. The stirring speed is 500 rpm, the stirring temperature is 50 °C, and after stirring for 0.8 h, perform ultrasonic treatment. The ultrasonic frequency is 45 kHz. After ultrasonic treatment for 0.8 h, obtain a fifth mixed solution;

[0060] S33. Continue to add proline and citric acid to the fifth mixed solution under stirring and stir for 0.8 h. At the same time, control the pH value to 7.0 with phosphate buffer saline, then continue to add gibberellin and continue to stir for 0.8 h to obtain a sixth mixed solution;

[0061] S34. Slowly add Bacillus subtilis liquid to the sixth mixed solution under low-speed stirring. Control the stirring speed at 225 rpm. After continuing to stir at room temperature for 15 min, filter through a 0.22 μm filter membrane to obtain the drought-resistant and saline-alkali-tolerant corn seed coating agent.

[0062] Example 2: This example discloses a drought-resistant and saline-alkali-tolerant corn seed coating agent, which comprises the following raw materials in parts by weight: 15 parts of nano-polyacrylamide, 7.5 parts of polyvinyl alcohol, 20 parts of modified MgAl-LDH, 0.6 part of gibberellin, 0.3 part of proline, 2 parts of citric acid, 15 parts of sodium carboxymethylcellulose, 8 parts of Bacillus subtilis, 55 parts of purified water. The drought-resistant and saline-alkali-tolerant corn seed coating agent further comprises Mo@ZIF-8. The weight ratio of Mo@ZIF-8 to modified MgAl-LDH is 5:20. The nano-size of Mo@ZIF-8 is 115 nm, and the specific surface area is 1335 m 2 / g.

[0063] The preparation method of the Mo@ZIF-8 comprises:

[0064] S11. Dissolve zinc nitrate in methanol under nitrogen protection and stirring to obtain a zinc nitrate solution. Then dissolve 2-methylimidazole and ammonium molybdate in methanol and stir for 1 h, and then slowly add the zinc nitrate solution while heating to 35 °C. Continue stirring and reacting for 24 h, and control the pH value to 10.5 with ammonia water. Let it stand for 15 h to obtain a first mixed solution;

[0065] S12. Centrifuge the first mixed solution at a high speed at 8000 rpm for 10 min. Wash the separated solid alternately with methanol and purified water for 3 times, and then perform vacuum drying at a drying temperature of 135 °C for 6 h to obtain Mo@ZIF-8 and grind it into a powder for standby.

[0066] The molar ratio of the zinc nitrate, 2-methylimidazole and ammonium molybdate is 1:8:0.02.

[0067] The preparation method of the modified MgAl-LDH includes:

[0068] S21. Dissolve magnesium nitrate and aluminum nitrate in purified water under stirring, control the molar ratio of Mg 2+ and Al 3+ to be 3:1, and prepare a 0.2 mol / L metal ion mixed solution;

[0069] S22. Slowly add 1 mol / L sodium hydroxide solution to the metal ion mixed solution under nitrogen protection and stirring until the pH value rises to 9.5, while heating to 65 °C. Continue stirring and reacting for 4 h, and then let it stand for 12 h to obtain a second mixed solution;

[0070] S23. Filter the second mixed solution by vacuum filtration. Wash the separated precipitate with purified water for 3 times and then perform vacuum drying at a drying temperature of 55 °C for 12 h to obtain MgAl-LDH and grind it into a powder for standby;

[0071] S24. Dissolve dopamine hydrochloride in phosphate buffered saline under nitrogen protection and stirring, stir for 0.5 h, then slowly add the MgAl-LDH powder while heating to 35 °C, and control the pH value to 8.5 with 0.1 mol / L sodium hydroxide solution. Continue stirring for 14 h to obtain a third mixed solution;

[0072] S25. Centrifuge the third mixed solution at a high speed at 8000 rpm for 10 min. Wash the separated solid with purified water for 3 times and then perform vacuum drying at a drying temperature of 65 °C for 12 h to obtain the modified MgAl-LDH and grind it into a powder for standby.

[0073] The nano-size of the modified MgAl-LDH is 110 nm, and the specific surface area is 135 m 2 / g.

[0074] The mass ratio of the MgAl-LDH to dopamine hydrochloride is 1:0.1.

[0075] A preparation method of a drought-resistant and saline-alkali-tolerant corn seed coating agent is applied to the drought-resistant and saline-alkali-tolerant corn seed coating agent, and includes the following steps:

[0076] S31. Add polyvinyl alcohol to purified water in a container and stir well, while heating to 75 - 85 °C. After stirring for 1 - 2 h, cool to 30 - 40 °C, then add sodium carboxymethylcellulose and continue stirring for 1 - 2 h. Control the stirring speed at 300 - 400 rpm. After cooling to room temperature, continue stirring at room temperature for 0.5 - 1 h to obtain a fourth mixed solution;

[0077] S32. Sequentially add nano-polyacrylamide, Mo@ZIF-8 and modified MgAl-LDH to the fourth mixed solution under stirring and stir evenly. The stirring speed is 400 rpm, the stirring temperature is 45 °C. After stirring for 0.5 h, perform ultrasonic treatment. The ultrasonic frequency is 40 kHz. After ultrasonic treatment for 0.5 h, obtain a fifth mixed solution;

[0078] S33. Continue to add proline and citric acid to the fifth mixed solution under stirring and stir for 0.5 h. At the same time, control the pH value to 6.5 with phosphate buffer saline. Then continue to add gibberellin and continue stirring for 0.5 h to obtain a sixth mixed solution;

[0079] S34. Slowly add Bacillus subtilis liquid to the sixth mixed solution under low-speed stirring. Control the stirring speed at 200 rpm. After continuing to stir at room temperature for 10 min, filter through a 0.22 μm filter membrane to obtain the drought-resistant and saline-alkali-tolerant corn seed coating agent.

[0080] Example 3: This example discloses a drought-resistant and saline-alkali-tolerant corn seed coating agent, which includes the following raw materials in parts by weight: 15 parts of nano-polyacrylamide, 7.5 parts of polyvinyl alcohol, 20 parts of modified MgAl-LDH, 0.6 part of gibberellin, 0.3 part of proline, 2 parts of citric acid, 15 parts of sodium carboxymethylcellulose, 8 parts of Bacillus subtilis, 55 parts of purified water. The drought-resistant and saline-alkali-tolerant corn seed coating agent also includes Mo@ZIF-8. The weight ratio of Mo@ZIF-8 to modified MgAl-LDH is 5:20. The nano-size of Mo@ZIF-8 is 120 nm, and the specific surface area is 1300 m 2 / g.

[0081] The preparation method of the Mo@ZIF-8 includes:

[0082] S11. Dissolve zinc nitrate in methanol under nitrogen protection and stirring to obtain a zinc nitrate solution. Then dissolve 2-methylimidazole and ammonium molybdate in methanol and stir for 2 h, and then slowly add the zinc nitrate solution while raising the temperature to 45 °C. Continue stirring and reacting for 26 h, and control the pH value to 11 with ammonia water. After standing for 18 h, a first mixed solution is obtained;

[0083] S12. Perform high-speed centrifugal separation on the first mixed solution at a rotation speed of 10,000 rpm for 15 min. The separated solid is washed alternately with methanol and purified water 3 times and then vacuum dried at a drying temperature of 145 °C for 8 h to obtain Mo@ZIF-8, which is ground into a powder and reserved.

[0084] The molar ratio of the zinc nitrate, 2-methylimidazole and ammonium molybdate is 1:10:0.04.

[0085] The preparation method of the modified MgAl-LDH includes:

[0086] S21. Dissolve magnesium nitrate and aluminum nitrate in purified water under stirring, control the molar ratio of Mg 2+ and Al 3+ to be 3:1, and prepare a 0.2 mol / L metal ion mixed solution;

[0087] S22. Slowly drop a 1 mol / L sodium hydroxide solution into the metal ion mixed solution under nitrogen protection and stirring until the pH value rises to 10.5, while raising the temperature to 75 °C. Continue stirring and reacting for 6 h, and then stand for 15 h to obtain a second mixed solution;

[0088] S23. Perform vacuum filtration separation on the second mixed solution. The separated precipitate is washed with purified water 3 times and then vacuum dried at a drying temperature of 65 °C for 15 h to obtain MgAl-LDH, which is ground into a powder and reserved;

[0089] S24. Dissolve dopamine hydrochloride in phosphate buffered saline under nitrogen protection and stirring, stir for 1 h, then slowly add the MgAl-LDH powder while raising the temperature to 45 °C, and control the pH value to 9 with a 0.1 mol / L sodium hydroxide solution. Continue stirring for 16 h to obtain a third mixed solution;

[0090] S25. Perform high-speed centrifugal separation on the third mixed solution at a rotation speed of 10,000 rpm for 15 min. The separated solid is washed with purified water 3 times and then vacuum dried at a drying temperature of 75 °C for 15 h to obtain the modified MgAl-LDH, which is ground into a powder and reserved.

[0091] The nano-size of the modified MgAl-LDH is 118 nm, and the specific surface area is 125 m 2 / g.

[0092] The mass ratio of the MgAl-LDH to dopamine hydrochloride is 1:0.3.

[0093] A preparation method of a drought-resistant and saline-alkali-tolerant corn seed coating agent is applied to the drought-resistant and saline-alkali-tolerant corn seed coating agent, and includes the following steps:

[0094] S31. Add polyvinyl alcohol to purified water in a container and stir well, while heating to 75-85 °C. After stirring for 1-2 h, cool to 30-40 °C, then add sodium carboxymethylcellulose and continue to stir for 1-2 h. Control the stirring speed at 300-400 rpm. After cooling to room temperature, continue to stir at room temperature for 0.5-1 h to obtain a fourth mixed solution;

[0095] S32. Add nano-polyacrylamide, Mo@ZIF-8 and modified MgAl-LDH to the fourth mixed solution in sequence under stirring and stir evenly. The stirring speed is 600 rpm, the stirring temperature is 55 °C, and after stirring for 1 h, perform ultrasonic treatment. The ultrasonic frequency is 50 kHz, and after ultrasonic treatment for 1 h, obtain a fifth mixed solution;

[0096] S33. Add proline and citric acid to the fifth mixed solution under stirring and stir for 1 h. At the same time, control the pH value to 7.5 with phosphate buffer saline, then continue to add gibberellin, and continue to stir for 1 h to obtain a sixth mixed solution;

[0097] S34. Slowly add Bacillus subtilis liquid to the sixth mixed solution under low-speed stirring. Control the stirring speed at 250 rpm, continue to stir at room temperature for 20 min, and then filter through a 0.22 μm filter membrane to obtain the drought-resistant and saline-alkali-tolerant corn seed coating agent.

[0098] Example 4: This example discloses a drought-resistant and saline-alkali-tolerant corn seed coating agent, which includes the following raw materials in parts by weight: 10 parts of nano-polyacrylamide, 5 parts of polyvinyl alcohol, 15 parts of modified MgAl-LDH, 0.2 part of gibberellin, 0.1 part of proline, 1 part of citric acid, 10 parts of sodium carboxymethylcellulose, 6 parts of Bacillus subtilis, 50 parts of purified water. The drought-resistant and saline-alkali-tolerant corn seed coating agent also includes Mo@ZIF-8. The weight ratio of Mo@ZIF-8 to modified MgAl-LDH is 5:15. The nano-size of Mo@ZIF-8 is 90 nm, and the specific surface area is 1380 m 2 / g. The preparation methods of Mo@ZIF-8 and modified MgAl-LDH in this example are the same as those in Example 1. The preparation method of a drought-resistant and saline-alkali-tolerant corn seed coating agent in this example is the same as that in Example 1.

[0099] Example 5: This example discloses a drought-resistant and saline-alkali-tolerant corn seed coating agent, which includes the following raw materials in parts by weight: 10 parts of nano-polyacrylamide, 5 parts of polyvinyl alcohol, 15 parts of modified MgAl-LDH, 0.2 part of gibberellin, 0.1 part of proline, 1 part of citric acid, 10 parts of sodium carboxymethylcellulose, 6 parts of Bacillus subtilis, 50 parts of purified water. The drought-resistant and saline-alkali-tolerant corn seed coating agent also includes Mo@ZIF-8. The weight ratio of Mo@ZIF-8 to modified MgAl-LDH is 5:15. The nano-size of Mo@ZIF-8 is 115 nm, and the specific surface area is 1335 m 2 / g. The preparation methods of Mo@ZIF-8 and modified MgAl-LDH in this example are the same as those in Example 2. The preparation method of a drought-resistant and saline-alkali-tolerant corn seed coating agent in this example is the same as that in Example 2.

[0100] Example 6: This example discloses a drought-resistant and saline-alkali-tolerant corn seed coating agent, which includes the following raw materials in parts by weight: 10 parts of nano-polyacrylamide, 5 parts of polyvinyl alcohol, 15 parts of modified MgAl-LDH, 0.2 part of gibberellin, 0.1 part of proline, 1 part of citric acid, 10 parts of sodium carboxymethylcellulose, 6 parts of Bacillus subtilis, 50 parts of purified water. The drought-resistant and saline-alkali-tolerant corn seed coating agent also includes Mo@ZIF-8. The weight ratio of Mo@ZIF-8 to modified MgAl-LDH is 5:15. The nano-size of Mo@ZIF-8 is 120 nm, and the specific surface area is 1300 m 2 / g. The preparation methods of Mo@ZIF-8 and modified MgAl-LDH in this example are the same as those in Example 3. The preparation method of a drought-resistant and saline-alkali-tolerant corn seed coating agent in this example is the same as that in Example 3.

[0101] Example 7: This example discloses a drought-resistant and saline-alkali-tolerant corn seed coating agent, which includes the following raw materials in parts by weight: 20 parts of nano-polyacrylamide, 10 parts of polyvinyl alcohol, 25 parts of modified MgAl-LDH, 1 part of gibberellin, 0.5 part of proline, 3 parts of citric acid, 20 parts of sodium carboxymethylcellulose, 10 parts of Bacillus subtilis, 60 parts of purified water. The drought-resistant and saline-alkali-tolerant corn seed coating agent also includes Mo@ZIF-8. The weight ratio of Mo@ZIF-8 to modified MgAl-LDH is 5:25. The nano-size of Mo@ZIF-8 is 90 nm, and the specific surface area is 1380 m 2 / g. The preparation methods of Mo@ZIF-8 and modified MgAl-LDH in this example are the same as those in Example 1. The preparation method of a drought-resistant and salt-tolerant corn seed coating agent in this example is the same as that in Example 1.

[0102] Example 8: This example discloses a drought-resistant and salt-tolerant corn seed coating agent, which includes the following raw materials in parts by weight: 20 parts of nano-polyacrylamide, 10 parts of polyvinyl alcohol, 25 parts of modified MgAl-LDH, 1 part of gibberellin, 0.5 part of proline, 3 parts of citric acid, 20 parts of sodium carboxymethylcellulose, 10 parts of Bacillus subtilis, and 60 parts of purified water. The drought-resistant and salt-tolerant corn seed coating agent also includes Mo@ZIF-8. The weight ratio of Mo@ZIF-8 to modified MgAl-LDH is 5:25. The nano-size of Mo@ZIF-8 is 115 nm, and the specific surface area is 1335 m 2 / g. The preparation methods of Mo@ZIF-8 and modified MgAl-LDH in this example are the same as those in Example 2. The preparation method of a drought-resistant and salt-tolerant corn seed coating agent in this example is the same as that in Example 2.

[0103] Example 9: This example discloses a drought-resistant and salt-tolerant corn seed coating agent, which includes the following raw materials in parts by weight: 20 parts of nano-polyacrylamide, 10 parts of polyvinyl alcohol, 25 parts of modified MgAl-LDH, 1 part of gibberellin, 0.5 part of proline, 3 parts of citric acid, 20 parts of sodium carboxymethylcellulose, 10 parts of Bacillus subtilis, and 60 parts of purified water. The drought-resistant and salt-tolerant corn seed coating agent also includes Mo@ZIF-8. The weight ratio of Mo@ZIF-8 to modified MgAl-LDH is 5:25. The nano-size of Mo@ZIF-8 is 120 nm, and the specific surface area is 1300 m 2 / g. The preparation methods of Mo@ZIF-8 and modified MgAl-LDH in this example are the same as those in Example 3. The preparation method of a drought-resistant and salt-tolerant corn seed coating agent in this example is the same as that in Example 3.

[0104] Control Group 1: The difference between this example and Example 1 is that it does not contain Mo@ZIF-8. This example discloses a drought-resistant and salt-tolerant corn seed coating agent, which includes the following raw materials in parts by weight: 15 parts of nano-polyacrylamide, 7.5 parts of polyvinyl alcohol, 20 parts of modified MgAl-LDH, 0.6 part of gibberellin, 0.3 part of proline, 2 parts of citric acid, 15 parts of sodium carboxymethylcellulose, 8 parts of Bacillus subtilis, and 55 parts of purified water. The preparation method of modified MgAl-LDH in this example is the same as that in Example 1. The preparation method of a drought-resistant and salt-tolerant corn seed coating agent in this example is the same as that in Example 1.

[0105] Control Group 2: The difference between this example and Example 1 is that it does not contain modified MgAl-LDH. This example discloses a drought-resistant and salt-tolerant corn seed coating agent, which includes the following raw materials in parts by weight: 15 parts of nano-polyacrylamide, 7.5 parts of polyvinyl alcohol, 0.6 part of gibberellin, 0.3 part of proline, 2 parts of citric acid, 15 parts of sodium carboxymethylcellulose, 8 parts of Bacillus subtilis, and 55 parts of purified water. The drought-resistant and salt-tolerant corn seed coating agent also includes Mo@ZIF-8, and the amount of Mo@ZIF-8 is [unspecified in the original]. The nano-size of the Mo@ZIF-8 is 90 nm, and the specific surface area is 1380 m 2 / g. The preparation method of Mo@ZIF-8 in this example is the same as that in Example 1. The preparation method of a drought-resistant and salt-tolerant corn seed coating agent in this example is the same as that in Example 1.

[0106] Control Group 3: The difference between this example and Example 1 is that it does not contain Mo@ZIF-8 and modified MgAl-LDH. This example discloses a drought-resistant and salt-tolerant corn seed coating agent, which includes the following raw materials in parts by weight: 15 parts of nano-polyacrylamide, 7.5 parts of polyvinyl alcohol, 0.6 part of gibberellin, 0.3 part of proline, 2 parts of citric acid, 15 parts of sodium carboxymethylcellulose, 8 parts of Bacillus subtilis, and 55 parts of purified water. The preparation method of a drought-resistant and salt-tolerant corn seed coating agent in this example is the same as that in Example 1.

[0107] Effect evaluation: Corn seedling growth experiment: Select mature and healthy corn seeds, and perform coating and drying treatment according to the usage method of the corn seed coating agent. The blank group is not coated. Set 13 seedling trays, fill equal amounts of disinfected soil in the seedling trays. The number of corn seeds in each experimental group is 30, the seed spacing is 3 cm, and the soil covering thickness is 2 cm. During the cultivation process, adopt a unified irrigation and topdressing system to ensure that the remaining planting management conditions are completely the same. After cultivating for 7 days, use a ruler to measure the plant height and root length, use a SPAD meter to measure the chlorophyll content, and use a leaf area meter to measure the leaf area. All values are recorded as the average value of each experimental group and are statistically shown in Table 1.

[0108]

[0109] Table 1 shows the statistical results of the growth of corn seeds in each experimental group. Plant height is an important indicator to measure the growth of crops, reflecting the overall growth potential and growth rate of crops; root length reflects the development status and growth ability of crop roots. Longer roots usually mean that the crop has better water and nutrient absorption ability; chlorophyll content is a direct reflection of the photosynthesis ability of crops. A higher chlorophyll content usually means a higher photosynthesis efficiency of the crop, which can produce nutrients more effectively; leaf area reflects the photosynthetic potential of crops. Crops with larger leaf areas usually have stronger photosynthesis ability and can synthesize more organic matter. As can be seen from Table 1, there are obvious differences in the growth of corn seeds in each experimental group. The growth index values of the corn seeds in the blank group are the lowest. By comparing the growth of the corn seeds in Example 1, Example 2, and Example 3, it can be found that different preparation conditions also have a certain impact on the growth of corn seeds. By comparing the growth of the corn seeds in Example 1, Example 4, and Example 7 with those in Control Groups 1-3, it can be found that overall, the growth of the corn seeds in Example 1, Example 4, and Example 7 is better. Among them, the growth of the corn seeds in Example 1 is the best, with a plant height of 12.7 cm, a root length of 11.2 cm, a chlorophyll content of 34.6, and a leaf area of 28.5 cm 2 , and when Mo@ZIF-8 and modified MgAl-LDH are added simultaneously when preparing the drought-resistant and salt-tolerant corn seed coating agent, the nutrients provided by this seed coating agent can effectively promote the growth of seedlings.

[0110] Saline-alkali drought stress experiment: Preparation of saline-alkali solution: Prepare a saline-alkali mixed solution with a concentration of 100 mM NaCl + 50 mM NaHCO 3 using purified water. Select mature and healthy corn seeds and perform coating and drying treatment according to the usage method of this corn seed coating agent. The blank group is not coated. Set up 13 seedling trays, fill the same amount of disinfected soil in the seedling trays, control the soil moisture content at about 30%, the number of corn seeds in each experimental group is 30, the seed spacing is 3 cm, and the soil covering thickness is 2 cm. At the beginning of cultivation, evenly spray the saline-alkali mixed solution on the seedling trays to simulate the saline-alkali environment, with a spraying amount of 10 mL, and spray once every 7 days. During the cultivation process, no watering is performed in all experimental groups to simulate the soil drought condition, ensuring that the remaining planting management conditions are exactly the same. Continue for 21 days. Measure the plant height with a ruler on the 7th, 14th, and 21st days. After the experiment, measure the root length of the seedlings with a ruler, measure the chlorophyll content with a SPAD meter, and measure the leaf area with a leaf area meter. All values are recorded as the average of each experimental group and statistically shown in Table 2.

[0111]

[0112] Table 2 shows the statistical results of the growth of corn seeds in each experimental group under saline-alkali and drought stress. It can be seen from Table 2 that under saline-alkali and drought stress, the growth of corn seeds in the blank group is poor and is significantly affected by , ion stress. Comparing the plant height of corn seedlings on the 7th day in each experimental group with that in the corn seedling growth experiment, the plant height value shows a decreasing trend, but it still remains at a relatively high level. After the experiment, comparing the growth of corn seeds in Example 1, Example 4, and Example 7 with those in Control Groups 1-3, it can be found that the growth of corn seeds in Example 1, Example 4, and Example 7 is better than that in Control Groups 1-3. Among them, the growth of corn seeds in Example 1 is the best, with a plant height of 19.5 cm, a root length of 10.8 cm, a chlorophyll content of 26.6, and a leaf area of 33.5 cm 2 . Therefore, when the drought-resistant and saline-alkali-tolerant corn seed coating agent prepared in Example 1 is used to coat corn seeds, the corn seeds show excellent drought resistance and saline-alkali tolerance.

[0113] Through the above limited experiments, the application effect of the drought-resistant and saline-alkali-tolerant corn seed coating agent in Example 1 of the present invention is remarkable. By optimizing the formula of the corn seed coating agent and adding Mo@ZIF-8 and modified MgAl-LDH during the production process in combination with modern nanotechnology, the two synergistically improve the drought resistance and saline-alkali tolerance of corn seeds, ensure the water absorption and germination of seeds in arid environments, reduce the inhibition of seed germination by saline-alkali stress, increase the seed germination rate, promote seedling growth, enhance stress resistance, and provide effective guarantee for the stable growth and high yield of corn under drought and saline-alkali stress environments.

[0114] Finally, it should be noted that although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A drought-resistant and salt-alkali-tolerant corn seed coating agent, characterized in that: The invention comprises the following raw materials in parts by weight: 10-20 parts of nano-polyacrylamide, 5-10 parts of polyvinyl alcohol, 15-25 parts of modified MgAl-LDH, 0.2-1 parts of gibberellin, 0.1-0.5 parts of proline, 1-3 parts of citric acid, 10-20 parts of sodium carboxymethyl cellulose, 6-10 parts of Bacillus subtilis, and 50-60 parts of purified water; The drought-resistant and salt-alkali-tolerant corn seed coating agent also includes: Mo@ZIF-8; The weight ratio of Mo@ZIF-8 to modified MgAl-LDH is 5:(15-25); The nanometer size of Mo@ZIF-8 is 85-125 nm, and the specific surface area is 1300-1400 m 2 / g; The preparation method of Mo@ZIF-8 comprises: S11. Under nitrogen protection and stirring, zinc nitrate is dissolved in methanol to obtain a zinc nitrate solution, and 2-methylimidazole and ammonium molybdate are dissolved in methanol together and stirred for 1-2 hours, and then the zinc nitrate solution is slowly added, and the temperature is raised to 35-45°C, and the stirring reaction is continued for 24-26 hours, and the pH value is controlled to 10.5-11 with ammonia water, and the first mixed solution is obtained after standing for 15-18 hours; S12. The first mixed solution was subjected to high-speed centrifugation at a speed of 8000-10000 rpm for 10-15 min, and the separated solid was washed alternately with methanol and purified water three times and then vacuum dried at a drying temperature of 135-145 ° C. After drying for 6-8 h, Mo@ZIF-8 was obtained and ground into powder for later use; The preparation method of the modified MgAl-LDH comprises: S21. Dissolve magnesium nitrate and aluminum nitrate in purified water under stirring, and control Mg 2+ and Al 3+ The molar ratio of is 3:1, and a 0.2 mol / L metal ion mixed solution is prepared; S22. Slowly add 1 mol / L sodium hydroxide solution to the metal ion mixed solution under nitrogen protection and stirring until the pH value rises to 9.5-10.5, and raise the temperature to 65-75°C, continue stirring and reacting for 4-6 hours, and then stand for 12-15 hours to obtain a second mixed solution; S23. The second mixed solution was separated by vacuum filtration, and the separated precipitate was washed three times with purified water and then vacuum dried at a drying temperature of 55 to 65 ° C. After drying for 12 to 15 hours, MgAl-LDH was obtained and ground into a powder for later use; S24. Dissolve dopamine hydrochloride in phosphate buffered saline under nitrogen protection and stirring, slowly add MgAl-LDH powder after stirring for 0.5-1h, raise the temperature to 35-45°C, and control the pH value to 8.5-9 with 0.1 mol / L sodium hydroxide solution, continue stirring for 14-16h to obtain a third mixed solution; S25. The third mixed solution was subjected to high-speed centrifugation at a speed of 8000 to 10000 rpm for 10 to 15 min. The separated solid was washed three times with purified water and then vacuum dried at a drying temperature of 65 to 75 ° C. After drying for 12 to 15 h, the modified MgAl-LDH was obtained and ground into a powder for standby use; The modified MgAl-LDH is obtained by grafting polydopamine on the surface of MgAl-LDH, and the nanometer size of the modified MgAl-LDH is 100-120 nm, and the specific surface area is 120-150 m 2 / g.

2. The drought-resistant and salt-alkali-tolerant corn seed coating agent according to claim 1, characterized in that: The molar ratio of the zinc nitrate, 2-methylimidazole and ammonium molybdate is 1:(8-10):(0.02-0.04).

3. The drought-resistant and salt-alkali-tolerant corn seed coating agent according to claim 1, characterized in that: The mass ratio of the MgAl-LDH to dopamine hydrochloride is 1:(0.1-0.3).

4. A method for preparing a drought-resistant and salt-alkali-tolerant corn seed coating agent, which is used to prepare the drought-resistant and salt-alkali-tolerant corn seed coating agent as claimed in any one of claims 1 to 3, characterized in that: The method comprises the following steps: S31. Add polyvinyl alcohol to purified water in a container and stir well, while heating to 75~85°C, stirring for 1~2h and then cooling to 30~40°C, then adding sodium carboxymethyl cellulose, controlling the stirring speed to 300~400 rpm, and continuing stirring at room temperature for 0.5~1h to obtain a fourth mixed solution; S32. Nano-polyacrylamide, Mo@ZIF-8 and modified MgAl-LDH were added to the fourth mixed solution in sequence under stirring, and the mixture was stirred evenly at a stirring speed of 400-600 rpm and a stirring temperature of 45-55° C. After stirring for 0.5-1 h, ultrasonic treatment was performed at a frequency of 40-50 kHz for 0.5-1 h to obtain a fifth mixed solution; S33. Proline and citric acid were added to the fifth mixed solution under stirring and stirred for 0.5 to 1 h, while the pH value was controlled at 6.5 to 7.5 with phosphate buffered saline, followed by the addition of gibberellin, and stirring was continued for 0.5 to 1 h to obtain a sixth mixed solution; S34. Slowly add the Bacillus subtilis solution to the sixth mixed solution under low-speed stirring, control the stirring speed to 200-250 rpm, continue stirring at room temperature for 10-20 minutes, and then filter through a 0.22 μm filter membrane to obtain the drought-resistant and salt-alkali-resistant corn seed coating agent.

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