A growth regulator for regulating cadmium absorption of rice and a preparation method thereof

Abstract

The present application belongs to the technical field of rice growth regulator, and relates to a growth regulator for regulating cadmium absorption of rice and a preparation method thereof. The growth regulator is prepared from calcium oxide nanoparticles, a silicon source, an iron source, a dispersing agent, a binder, a carrier and a complexing agent. The preparation method comprises the following steps: the silicon source is prepared into a silicate aqueous solution, the iron source and the complexing agent are prepared into an iron salt complex aqueous solution; the dispersing agent and the calcium oxide nanoparticles are added into the silicate solution to form a silicon-calcium composite shell layer; then the iron salt complex solution is added dropwise to make trivalent iron ions hydrolyze into nano-hydroxyl ferric oxide and be loaded on the surface of the shell layer through silicon-oxygen-iron bonds; and finally, drying and granulation are performed. The present application realizes long-acting and slow-release of calcium by using the silicon-calcium shell layer, promotes the formation of the root surface iron film by using nano-hydroxyl ferric oxide, and cooperatively reduces the available cadmium in the soil and inhibits the absorption of the rice.

Description

Technical Field

[0001] This invention belongs to the field of rice growth regulator technology, and relates to a growth regulator for controlling cadmium absorption in rice and its preparation method. Background Technology

[0002] Among existing technologies for controlling cadmium pollution in paddy fields, the application of calcium-based materials such as quicklime is the most commonly used passivation measure. The principle is to increase soil pH to promote the formation of Cd hydroxide precipitates and reduce the bioavailability of Cd in the soil. However, traditional calcium-based materials have significant technical bottlenecks: First, the mechanism of action is singular, relying solely on the pH passivation effect at the soil end, and cannot regulate the Cd absorption, translocation, and detoxification process of rice itself, resulting in a low upper limit for cadmium reduction efficiency; second, the materials have low activity and require large amounts, and long-term application can easily lead to soil compaction, excessive alkalization and re-acidification, and also poses a risk of burning seedlings; third, the effect is not timely, the materials diffuse slowly, and it is difficult to accurately match the critical growth period of rice cadmium uptake.

[0003] With the development of nanotechnology, nano-metal oxides have begun to be applied to the remediation of heavy metals in farmland. However, existing nano-calcium-based materials still have many shortcomings: First, they are mostly developed as soil passivators, without exploring their physiological regulatory functions as plant growth regulators, and without achieving systematic regulation of the soil-rice system. Second, single nanomaterials are prone to aggregation and have short action cycles. Moreover, they rely solely on the adsorption and passivation functions of the materials themselves, which is a simple superposition of component functions and does not build a synergistic effect system at the chemical reaction level. Third, existing formulations do not incorporate the design of the critical window period for Cd absorption in rice, making it difficult to simultaneously achieve multi-level linkage of soil passivation, root surface interception, and plant detoxification, resulting in unstable effects in actual field applications.

[0004] Therefore, there is an urgent need to develop a new type of plant growth regulator to break through the technical bottleneck of traditional calcium-based materials and provide an efficient, safe, and sustainable technical solution for the safe control of cadmium in rice from acidic paddy fields in southern China. Summary of the Invention

[0005] In view of the problems existing in the prior art, the present invention provides a growth regulator for controlling cadmium absorption in rice and its preparation method. This method uses calcium oxide nanoparticles as the core, utilizing the calcium ions released by their hydrolysis to react in situ with a silicon source to construct a calcium silicate composite shell, achieving long-term sustained release of alkaline substances. Furthermore, a complexing agent is introduced to regulate the hydrolysis process of ferric ions, allowing nano-FeOOH to be chemically bonded and directionally loaded onto the shell surface, thereby preparing a composite growth regulator that combines long-term sustained release, root surface physical barrier control, and rhizosphere chemical passivation functions.

[0006] To achieve the above and other objectives, the technical solution adopted by the present invention is as follows:

[0007] This invention provides a growth regulator for controlling cadmium absorption in rice. The growth regulator is prepared from the following raw materials in parts by weight: 68-78 parts calcium oxide nanoparticles, 5-10 parts silicon source, 3-6 parts iron source, 0.5-1.5 parts dispersant, 3-5 parts binder, 3-8 parts carrier, and 0.5-1.5 parts complexing agent.

[0008] Furthermore, the calcium oxide nanoparticles (CaONPs) have a particle size of 50-100 nm and a purity of ≥99%. As the core for alkalinity regulation and a source of calcium ions, they slowly hydrolyze in the soil to release OH-. - Increase pH and release Ca 2+ Competitive root system Cd 2+ Absorption sites.

[0009] Furthermore, the silicon source is either potassium silicate or sodium silicate.

[0010] Furthermore, the iron source is ferric chloride hexahydrate (FeCl3·6H2O).

[0011] Furthermore, the complexing agent is at least one selected from sodium citrate and sodium tartrate, used to react with Fe. 3+ To form stable complexes, control their hydrolysis rate, avoid the formation of large flocculent Fe(OH)3, and promote the directional loading of nano-FeOOH.

[0012] Furthermore, the dispersant is polyvinylpyrrolidone, used to inhibit nanoparticle aggregation during ultrasonic dispersion and ensure particle uniformity.

[0013] Furthermore, the binder is at least one of carboxymethyl cellulose, starch, and polyvinyl alcohol.

[0014] Furthermore, the carrier is at least one of diatomaceous earth and bentonite.

[0015] This invention also provides a method for preparing a growth regulator that controls cadmium absorption in rice, comprising the following steps:

[0016] S1: Dissolve the silicon source in deionized water to prepare a silicate aqueous solution with a mass concentration of 12%-18%, dissolve the iron source in deionized water to prepare an iron salt aqueous solution with a mass concentration of 5%-8%, add a complexing agent to the iron salt aqueous solution, the molar ratio of the complexing agent to the iron source is 0.5-1:1, and stir until completely dissolved to obtain an iron salt complexed aqueous solution;

[0017] S2: Add the dispersant to the silicate aqueous solution obtained in step S1. Under ice-water bath cooling conditions, slowly add calcium oxide nanoparticles in batches at a rate of 0.5-1 g / min, controlling the solid-liquid mass ratio to be 1:2.5-3.5. Then, heat to 50-60℃ and ultrasonically disperse for 30-60 minutes to allow silicate ions to react with CaONPs and release Ca. 2+ A reaction occurs, forming a silicon-calcium composite shell on the surface of CaONPs, followed by aging at room temperature for 4-8 hours to obtain slurry a;

[0018] S3: Under stirring conditions, the iron salt complex aqueous solution obtained in step S1 is slowly added dropwise to the slurry a obtained in step S2 at a rate of 0.5-2 mL / min, utilizing the large amount of OH released by the hydrolysis of CaONPs in slurry a. - Maintain an alkaline environment in the system, and then continue stirring the reaction at 40-60℃ for 2-4 hours. During this process, Fe... 3+ The complex formed with the complexing agent is slowly hydrolyzed under alkaline conditions to form nano-FeOOH, which is then oriented and loaded onto the surface of the silicon-calcium composite shell through Si-O-Fe bonding to obtain slurry b;

[0019] S4: The slurry b obtained in step S3 is vacuum dried at 40-50℃ for 8-16 hours, and then ground through a 200-mesh sieve to obtain composite nanopowder;

[0020] S5: Add the carrier and binder to the composite nanopowder obtained in step S4, mix evenly, and then granulate to obtain granules with a particle size of 2-4 mm, i.e., the growth regulator.

[0021] The present invention also provides the application of the above-mentioned growth regulator in regulating cadmium absorption and enrichment in rice.

[0022] Furthermore, the application includes the following steps: applying the growth regulator at a rate of 1.2-1.8 g / kg dry soil (calculated as CaONPs) evenly to cadmium-contaminated acidic paddy soil 7-10 days before rice transplanting and mixing thoroughly, then flooding the soil and maintaining a 3-5 cm water layer for 25-30 days before transplanting the rice.

[0023] Furthermore, the growth regulator is particularly suitable for acidic cadmium-contaminated paddy soils with a pH of 4.5-6.0, under which its buffering effect on soil pH and its promoting effect on silicon absorption by rice are particularly significant.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] This invention successfully constructed a ternary composite structure of calcium, silicon, and iron through a rational raw material formulation and step-by-step assembly process, achieving multi-faceted synergistic inhibition of cadmium absorption in rice. Specifically, in the preparation process, the Ca released by the hydrolysis of calcium oxide nanoparticles is first utilized... 2+ An in-situ reaction occurs with silicate ions, forming a calcium silicate composite shell on the particle surface. This shell acts as a physical barrier, delaying the contact between water molecules and the CaO core, thus solving the problems of traditional lime materials rapidly releasing strong alkali upon contact with water, easily causing seedling burn, and having unsustainable remediation effects. Subsequently, through complexing agents such as sodium citrate and Fe... 3+ A stable complex is formed, and its slow hydrolysis is controlled under alkaline conditions, allowing nano-FeOOH to be oriented and loaded onto the shell surface via Si-O-Fe bonding, thus avoiding the formation of Fe... 3+ The problem of direct hydrolysis generating large Fe(OH)3 precipitates and thus failing is addressed. In field application, flooding conditions induce the loaded iron oxides to promote the in-situ formation of iron film on the rice root surface, achieving an improvement from single soil passivation to a synergistic effect of soil passivation and root surface inhibition.

[0026] Thanks to the above design, the growth regulator of this invention exhibits the following comprehensive properties: First, the physical barrier effect of the calcium silicate composite shell ensures the long-term slow release of calcium oxide nanoparticles in the soil, maintaining the long-term stability of the rhizosphere micro-domain pH and avoiding the problem of unsustainable remediation effects caused by the rapid onset and decay of traditional lime materials; second, the Cd in the soil solution... 2+ On the one hand, the OH- is released slowly - On the one hand, Cd is fixed by precipitation; on the other hand, it is efficiently retained by the iron film formed in situ on the root surface through surface complexation and co-precipitation, blocking the absorption of Cd. 2+ The pathway of cadmium transport into the root demonstrates significantly better cadmium reduction efficiency than single materials; furthermore, the orthosilicic acid slowly released from the silicon-calcium shell is absorbed by rice and deposited on the cell wall, enhancing the mechanical strength of the cell wall and thus strengthening its ability to reduce Cd. 2+ Its fixation ability, combined with the release of Ca 2+ At root absorption sites and Cd 2+ This generates competitive antagonism, further reducing the absorption of cadmium by rice, providing an efficient, safe, and easily promoted technical solution for the safe utilization of acid cadmium-contaminated paddy fields. Attached Figure Description

[0027] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below.

[0028] Figure 1 Figure showing the results of the measurement of the effects of different treatments on soil pH at maturity;

[0029] Figure 2 The figure shows the results of measuring the effect of different treatments on the available cadmium content in the soil according to the present invention.

[0030] Figure 3 Cd translocation coefficients in different parts of mature rice under different treatments;

[0031] Figure 4 The Cd content in the root and stem subcellular components of rice at maturity under different treatments is shown in Figure 1. Where a represents the root subcellular component and b represents the stem subcellular component.

[0032] Figure 5 The diagram shows the subcellular distribution patterns of Cd in the roots and stems of rice at maturity under different treatments, where a represents root subcells and b represents stem subcells. Detailed Implementation

[0033] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those familiar to those skilled in the art. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to this invention. The preferred embodiments and materials described herein are for illustrative purposes only and do not limit the scope of this application.

[0035] Unless otherwise specified, all materials used in the following implementation are new materials purchased from the market. Among them, the calcium oxide nanoparticles have a particle size of 50-100nm and a purity of ≥99%, and the ferric chloride hexahydrate is of analytical grade.

[0036] Example 1: This example provides a growth regulator for controlling cadmium absorption in rice. The growth regulator is prepared from the following raw materials in parts by weight: 73 parts calcium oxide nanoparticles, 7.5 parts potassium silicate, 4.5 parts ferric chloride hexahydrate, 1.0 part polyvinylpyrrolidone, 4.0 parts sodium carboxymethyl cellulose, 5.5 parts bentonite, and 1.0 part sodium citrate.

[0037] The preparation method of the above-mentioned growth regulator is as follows:

[0038] S1. First, weigh 7.5 parts of potassium silicate and dissolve it in an appropriate amount of deionized water. Stir on a magnetic stirrer for 30 minutes until completely dissolved to prepare a silicate aqueous solution with a mass concentration of 15%. Second, weigh 4.5 parts of ferric chloride hexahydrate and dissolve it in an appropriate amount of deionized water to prepare an iron salt aqueous solution with a mass concentration of 6.5%. Add 1.0 part of sodium citrate to the iron salt aqueous solution and stir at 300 rpm for 20 minutes at room temperature until the solution is clear and transparent to obtain an iron salt complex aqueous solution.

[0039] S2. Add 1.0 part of polyvinylpyrrolidone to the silicate aqueous solution obtained in S1 and stir to dissolve it completely. Then, place the mixed solution in an ice-water bath to cool to 5°C. Under the conditions of ice bath cooling and continuous stirring, slowly add 73 parts of calcium oxide nanoparticles to the above solution in batches at a rate of 0.8 g / min, controlling the solid-liquid mass ratio to be 1:3. After the addition is completed, remove the mixed system from the ice bath, heat it to 55°C and ultrasonically disperse it for 45 minutes. After ultrasonic treatment, let the slurry stand at room temperature for 6 hours to obtain slurry a.

[0040] S3: Under mechanical stirring, the iron salt complex aqueous solution obtained in S1 is transferred to a constant pressure dropping funnel and slowly added dropwise to the slurry a obtained in step S2 at a rate of 1.5 mL / min. After the addition is completed, the system temperature is controlled at 50℃ and the reaction is continued at 300 rpm for 3 hours to obtain slurry b.

[0041] S4: Place the slurry b obtained in step S3 in a vacuum drying oven and vacuum dry it at 45°C for 12 hours. Then take out the dried block solid and grind it using a planetary ball mill. After grinding, pass it through a 200-mesh standard sieve to obtain composite nanopowder.

[0042] S5: Add 5.5 parts of bentonite and 4.0 parts of sodium carboxymethyl cellulose to the composite nanopowder obtained in step S4. Place the mixture in a V-type mixer and mix for 30 minutes to ensure that the components are mixed evenly. Then, put the mixed powder into a rotary granulator, add an appropriate amount of deionized water as a wetting agent, and granulate to obtain spherical granules with a particle size of about 3 mm. Dry the granulated wet granules at 40°C to obtain the growth regulator.

[0043] Example 2: This example provides a growth regulator for controlling cadmium absorption in rice. The growth regulator is prepared from the following raw materials in parts by weight: 78 parts calcium oxide nanoparticles, 10 parts sodium silicate, 6.0 parts ferric chloride hexahydrate, 1.5 parts polyvinylpyrrolidone, 5.0 parts starch, 8.0 parts diatomaceous earth, and 1.5 parts sodium tartrate.

[0044] The preparation method of the above-mentioned growth regulator is as follows:

[0045] S1. First, weigh 10 parts of sodium silicate and dissolve it in an appropriate amount of deionized water. Stir on a magnetic stirrer for 30 minutes until completely dissolved to prepare a silicate aqueous solution with a mass concentration of 18%. Second, weigh 6.0 parts of ferric chloride hexahydrate and dissolve it in an appropriate amount of deionized water to prepare an iron salt aqueous solution with a mass concentration of 8%. Add 1.5 parts of sodium tartrate to the iron salt aqueous solution and stir at 300 rpm for 20 minutes at room temperature until the solution is clear and transparent to obtain an iron salt complex aqueous solution.

[0046] S2. Add 1.5 parts of polyvinylpyrrolidone to the silicate aqueous solution obtained in S1 and stir until fully dissolved. Then, place the mixed solution in an ice-water bath to cool to 5°C. Under the conditions of ice bath cooling and continuous stirring, slowly add 78 parts of calcium oxide nanoparticles to the above solution in batches at a rate of 1.0 g / min, controlling the solid-liquid mass ratio to be 1:3.5. After the addition is completed, remove the mixed system from the ice bath, heat it to 60°C and ultrasonically disperse it for 60 minutes. After ultrasonic treatment, let the slurry stand at room temperature for 8 hours to obtain slurry a.

[0047] S3. Under mechanical stirring, the iron salt complex aqueous solution prepared in S1 is transferred to a constant pressure dropping funnel and slowly added dropwise to the slurry a obtained in step S2 at a rate of 2.0 mL / min. After the addition is completed, the system temperature is controlled at 60℃ and the reaction is continued at a speed of 300 rpm for 4 hours to obtain slurry b.

[0048] S4. Place the slurry b obtained in step S3 in a vacuum drying oven and vacuum dry it at 50°C for 16 hours. Then take out the dried block solid and grind it using a planetary ball mill. After grinding, pass it through a 200-mesh standard sieve to obtain composite nanopowder.

[0049] S5. Add 8.0 parts of diatomaceous earth and 5.0 parts of starch to the composite nanopowder obtained in step S4. Place the mixture in a V-type mixer and mix for 30 minutes to ensure that the components are mixed evenly. Then, put the mixed powder into a rotary granulator, add an appropriate amount of deionized water as a wetting agent, and granulate to obtain spherical granules with a particle size of about 4 mm. Dry the granulated wet granules at 40°C to obtain the growth regulator.

[0050] Example 3: This example provides a growth regulator for controlling cadmium absorption in rice. The growth regulator is prepared from the following raw materials in parts by weight: 68 parts calcium oxide nanoparticles, 5 parts potassium silicate, 3.0 parts ferric chloride hexahydrate, 0.5 parts polyvinylpyrrolidone, 3.0 parts polyvinyl alcohol, 3.0 parts bentonite, and 0.5 parts sodium citrate.

[0051] The preparation method of the above-mentioned growth regulator is as follows:

[0052] S1. First, weigh 5 parts of potassium silicate and dissolve them in an appropriate amount of deionized water. Stir on a magnetic stirrer for 30 minutes until completely dissolved to prepare a silicate aqueous solution with a mass concentration of 12%. Second, weigh 3.0 parts of ferric chloride hexahydrate and dissolve them in an appropriate amount of deionized water to prepare an iron salt aqueous solution with a mass concentration of 5%. Add 0.5 parts of sodium citrate to the iron salt aqueous solution and stir at 300 rpm for 20 minutes at room temperature until the solution is clear and transparent to obtain an iron salt complex aqueous solution.

[0053] S2. Add 0.5 parts of polyvinylpyrrolidone to the silicate aqueous solution obtained in S1, stir to dissolve completely, and then place the mixed solution in an ice-water bath to cool to 5°C. Under the conditions of ice bath cooling and continuous stirring, slowly add 68 parts of calcium oxide nanoparticles to the above solution in batches at a rate of 0.5 g / min, controlling the solid-liquid mass ratio to be 1:2.5. After the addition is complete, remove the mixed system from the ice bath, heat to 50°C and ultrasonically disperse for 30 minutes. After ultrasonic treatment, let the slurry stand at room temperature for 4 hours to obtain slurry a;

[0054] S3. Under mechanical stirring, the iron salt complex aqueous solution obtained in S1 is transferred to a constant pressure dropping funnel and slowly added dropwise to slurry a obtained in step S2 at a rate of 0.5 mL / min. After the addition is complete, the system temperature is controlled at 40℃, and the reaction is continued to be stirred at 300 rpm for 2 hours to obtain slurry b;

[0055] S4. Place the slurry b obtained in step S3 in a vacuum drying oven and vacuum dry it at 40°C for 8 hours. Then, take out the dried block solid, grind it using a planetary ball mill, and pass it through a 200-mesh standard sieve to obtain composite nanopowder.

[0056] S5. Add 3.0 parts bentonite and 3.0 parts polyvinyl alcohol to the composite nanopowder obtained in step S4. Place the mixture in a V-type mixer and mix for 30 minutes to ensure that the components are mixed evenly. Then, put the mixed powder into a rotary granulator, add an appropriate amount of deionized water as a wetting agent, and granulate to obtain spherical granules with a particle size of about 2 mm. Dry the granulated wet granules at 40°C to obtain the growth regulator.

[0057] Example 4: This example provides a growth regulator for controlling cadmium absorption in rice. The growth regulator is prepared from the following raw materials in parts by weight: 75 parts calcium oxide nanoparticles, 6 parts sodium silicate, 4.0 parts ferric chloride hexahydrate, 1.0 part polyvinylpyrrolidone, 4.0 parts starch, 6.0 parts bentonite, and 1.0 part sodium citrate.

[0058] The preparation method of the above-mentioned growth regulator is as follows:

[0059] S1. First, weigh 6 parts of sodium silicate and dissolve them in an appropriate amount of deionized water. Stir on a magnetic stirrer for 30 minutes until completely dissolved to prepare a 14% (w / w) silicate aqueous solution. Second, weigh 4.0 parts of ferric chloride hexahydrate and dissolve them in an appropriate amount of deionized water to prepare a 6% (w / w) ferric salt aqueous solution. Add 1.0 part of sodium citrate to this ferric salt aqueous solution and stir at 300 rpm for 20 minutes at room temperature until the solution is clear and transparent to obtain a ferric salt complex aqueous solution.

[0060] S2. Add 1.0 part of polyvinylpyrrolidone to the silicate aqueous solution obtained in S1 and stir until fully dissolved. Then, place the mixed solution in an ice-water bath to cool to 5°C. Under the conditions of ice bath cooling and continuous stirring, slowly add 75 parts of calcium oxide nanoparticles to the above solution in batches at a rate of 0.8 g / min, controlling the solid-liquid mass ratio to be 1:3. After the addition is complete, remove the mixed system from the ice bath, heat it to 55°C, and ultrasonically disperse it for 45 minutes. After ultrasonic treatment, let the slurry stand at room temperature for 6 hours to obtain slurry a;

[0061] S3. Under mechanical stirring, the iron salt complex aqueous solution prepared in S1 is transferred to a constant pressure dropping funnel and slowly added dropwise to the slurry a obtained in step S2 at a rate of 1.0 mL / min. After the addition is complete, the system temperature is controlled at 50℃, and the reaction is continued to be stirred at 300 rpm for 3 hours to obtain slurry b;

[0062] S4. Place the slurry b obtained in step S3 in a vacuum drying oven and vacuum dry it at 45°C for 12 hours. Then, take out the dried block solid, grind it using a planetary ball mill, and pass it through a 200-mesh standard sieve to obtain composite nanopowder.

[0063] S5. Add 6.0 parts of bentonite and 4.0 parts of starch to the composite nanopowder obtained in step S4. Place the mixture in a V-type mixer and mix for 30 minutes to ensure that all components are mixed evenly. Then, put the mixed powder into a rotary granulator, add an appropriate amount of deionized water as a wetting agent, and granulate to obtain spherical granules with a particle size of about 3 mm. Dry the granulated wet granules at 40°C to obtain the growth regulator.

[0064] Example 5: This example provides a growth regulator for controlling cadmium absorption in rice. The growth regulator is prepared from the following raw materials in parts by weight: 70 parts calcium oxide nanoparticles, 8 parts potassium silicate, 4.0 parts ferric chloride hexahydrate, 1.2 parts polyvinylpyrrolidone, 4.5 parts sodium carboxymethyl cellulose, 5.0 parts diatomaceous earth, and 1.2 parts sodium tartrate.

[0065] The preparation method of the above-mentioned growth regulator is as follows:

[0066] S1. First, weigh 8 parts of potassium silicate and dissolve them in an appropriate amount of deionized water. Stir on a magnetic stirrer for 30 minutes until completely dissolved to prepare a 16% (w / w) silicate aqueous solution. Second, weigh 4.0 parts of ferric chloride hexahydrate and dissolve them in an appropriate amount of deionized water to prepare a 7% (w / w) ferric salt aqueous solution. Add 1.2 parts of sodium tartrate to this ferric salt aqueous solution and stir at 300 rpm for 20 minutes at room temperature until the solution is clear and transparent to obtain a ferric salt complex aqueous solution.

[0067] S2. Add 1.2 parts of polyvinylpyrrolidone to the silicate aqueous solution obtained in S1 and stir until fully dissolved. Then, place the mixed solution in an ice-water bath to cool to 5°C. Under the conditions of ice bath cooling and continuous stirring, slowly add 70 parts of calcium oxide nanoparticles to the above solution in batches at a rate of 0.8 g / min, controlling the solid-liquid mass ratio to be 1:3. After the addition is complete, remove the mixed system from the ice bath, heat it to 58°C, and ultrasonically disperse it for 50 minutes. After ultrasonic treatment, let the slurry stand at room temperature for 6 hours to obtain slurry a;

[0068] S3. Under mechanical stirring, the iron salt complex aqueous solution obtained in S1 is transferred to a constant pressure dropping funnel and slowly added dropwise to slurry a obtained in step S2 at a rate of 1.5 mL / min. After the addition is complete, the system temperature is controlled at 55℃, and the reaction is continued to be stirred at 300 rpm for 3 hours to obtain slurry b;

[0069] S4. Place the slurry b obtained in step S3 in a vacuum drying oven and vacuum dry it at 48°C for 12 hours. Then, take out the dried block solid, grind it using a planetary ball mill, and pass it through a 200-mesh standard sieve to obtain composite nanopowder.

[0070] S5. Add 5.0 parts of diatomaceous earth and 4.5 parts of sodium carboxymethyl cellulose to the composite nanopowder obtained in step S4. Place the mixture in a V-type mixer and mix for 30 minutes to ensure that the components are mixed evenly. Then, put the mixed powder into a rotary granulator, add an appropriate amount of deionized water as a wetting agent, and granulate to obtain spherical granules with a particle size of about 3 mm. Dry the granulated wet granules at 40°C to obtain the growth regulator.

[0071] Comparative Example 1: This comparative example provides a regulator prepared by physical mixing. The types and weight parts of the raw materials are exactly the same as those in Example 1, but the preparation method is modified as follows: all the above solid raw materials are directly placed in a high-speed mixer for physical mixing for 20 minutes, then an appropriate amount of water is added for granulation and drying. The chemical reaction process of steps S1-S4 is not carried out, and the raw materials are combined only by simple physical mixing.

[0072] Comparative Example 2: This comparative example provides a growth regulator that uses ordinary calcium oxide instead of calcium oxide nanoparticles. The formulation and preparation method are the same as in Example 1, except that the calcium oxide nanoparticles are replaced with an equal mass of ordinary calcium oxide.

[0073] Comparative Example 3: This comparative example provides a growth regulator without complexing agents, with the following formulation: 73 parts calcium oxide nanoparticles, 7.5 parts potassium silicate, 4.5 parts ferric chloride hexahydrate, 1.0 part polyvinylpyrrolidone, 4.0 parts sodium carboxymethyl cellulose, and 5.5 parts bentonite. The preparation method is as follows: potassium silicate is prepared into a silicate aqueous solution according to the method of Example 1, polyvinylpyrrolidone is added, CaONPs are added under ice bath conditions, the temperature is raised to 55°C and ultrasonically dispersed for 45 minutes, and aged for 6 hours. Ferric chloride hexahydrate is directly dissolved in deionized water and added dropwise to slurry a at a rate of 1.5 mL / min, and reacted at 50°C for 3 hours. Subsequent steps are the same as in Example 1.

[0074] 1. Experimental materials:

[0075] (1) Test soil: Cadmium-contaminated soil from a farmland in Guangdong Province was collected. After collection, the soil sample was transported to the Dafeng Base of Guangdong Academy of Agricultural Sciences. After removing gravel, plant debris and other impurities, it was air-dried and passed through a 2mm sieve for later use. Its physicochemical properties are shown in Table 1.

[0076] Table 1. Basic physicochemical properties of the tested soils

[0077]

[0078] (2) Rice variety tested: Nan Jing Xiang Zhan (temperature-sensitive indica conventional rice variety).

[0079] (3) Test flower pot: round bottom flower pot, with a size of 20cm×25cm.

[0080] 2. Experimental Design:

[0081] (1) The experiment was set up with 7 treatment groups, each treatment was repeated 4 times (i.e. 4 pots). CK group: blank control, only basal fertilizer was applied, and no growth regulator was applied; Example 1 group: growth regulator prepared in Example 1 was applied; Example 2 group: growth regulator prepared in Example 2 was applied; Example 3 group: growth regulator prepared in Example 3 was applied; Comparative Example 1 group: physical mixed growth regulator prepared in Comparative Example 1 was applied; Comparative Example 2 group: ordinary calcium oxide growth regulator prepared in Comparative Example 2 was applied; Comparative Example 3 group: growth regulator without complexing agent was applied.

[0082] (2) Application method: Each regulator treatment group was applied at a dosage of 1.5 g / kg dry soil based on the equivalent calcium oxide nanoparticle content. The regulator and base fertilizer (1.5 g / kg soil urea, 1.1 g / kg soil potassium dihydrogen phosphate) were thoroughly mixed with 5 kg of soil in a plastic pot. The CK group was mixed with only base fertilizer. The treated soil was placed in round-bottomed plastic flower pots (20 cm in diameter, 25 cm in height), deionized water was added and a water layer of about 3 cm was maintained. The soil was left to stand for 30 days to reach equilibrium. After the 30 days, rice seedlings with uniform growth were selected for transplanting. At the same time, soil solution samplers were buried in different soil layers (5 cm, 10 cm) and kept in an appropriate position throughout the experiment to ensure in-situ collection without interference. Then, deionized water was added to the soil and the soil was covered with water at a depth of about 3 cm throughout the growing season to simulate the flooding state of the paddy field.

[0083] 3. Sample collection and index determination:

[0084] (1) Destructive sampling during the rice ripening period:

[0085] ① Rhizosphere soil was collected, air-dried, and sieved as experimental soil samples. The soil pH was then determined using a potentiometric method. The results are as follows: Figure 1 As shown; DTPA extraction was performed using a DTPA extractant (pH 7.3), with shaking for 2 hours. After filtration, the content of available cadmium (DTAP-Cd) in the soil was determined using inductively coupled plasma mass spectrometry (ICP-MS). The results are as follows. Figure 2 As shown.

[0086] ② The whole rice plant was removed, rinsed repeatedly with tap water and deionized water, and the surface moisture was wiped off to obtain a rice sample. The rice roots, stems, leaves, and grains were separated, blanched at 105℃ for 30 minutes, dried at 70℃ to constant weight, pulverized and sieved, and then digested using HNO3-HClO4 digestion method. The Cd content of each part of the rice was determined by ICP-MS, and the results are shown in Table 2.

[0087] Table 2. Results of cadmium content determination in different parts of rice.

[0088]

[0089] Depend on Figure 1 It was found that at a soil depth of 5 cm, the soil pH of each treatment group ranged from 7.66 to 7.76, all higher than that of the CK group and the comparative group; at a soil depth of 10 cm, the soil pH of each treatment group ranged from 7.93 to 8.03, all higher than that of the CK group and the comparative group. The comparative group 2 performed the worst overall, significantly lower than the groups in each example, indicating that nanoscale CaONPs can more effectively release OH groups into deeper soil layers. - This increases soil pH.

[0090] The content of available cadmium directly reflects the soil's ability to migrate with cadmium and the risk of it being absorbed by plants. Experimental results are as follows: Figure 2 As shown, the embodiments of this invention exhibit excellent performance in reducing available cadmium in soil. Compared with the control group, the DTPA-Cd content in the soil of each embodiment group was significantly reduced, with a reduction range of 17% to 20%. This significant passivation effect is attributed to the synergistic adsorption effect of the in-situ generated silicon-calcium composite shell in the regulator and nano-FeOOH, effectively removing Cd. 2+ It transforms into a sparingly soluble state.

[0091] The experimental data in Table 2 show that the Cd content in each embodiment group was significantly reduced in all parts of rice, especially the Cd content in the roots, which was significantly lower than that in the control group and the control (CK). This indicates that the regulator of the present invention reduces the entry of Cd into rice root cells at the source by intercepting iron film on the root surface and changing the rhizosphere environment, thereby blocking the translocation to the grains and ultimately achieving a safe level of Cd content in the grains.

[0092] (2) Rice transcriptome analysis

[0093] To further investigate the molecular mechanism of the growth regulator of this invention in response to Cd stress in rice, transcriptome sequencing and analysis were performed on various parts of mature rice. Total RNA was extracted from the samples, and rRNA was removed using a standard kit, enriching the mRNA. The enriched mRNA was then reverse transcribed to form double-stranded cDNA. After repairing the double-ended ends of the cDNA, adapters were added, and PCR amplification was performed to construct a library. One-way ANOVA was used for multiple comparisons to assess the significance (P < 0.05) between different treatments. Pearson correlation analysis was used, and the rice translocation coefficient (TF) was used to assess the rice's ability to absorb and translocate Cd. The formula for calculating the translocation coefficient (TF) is: TF = , i represents the next site of Cd migration in rice, j represents the previous site of Cd migration; Ci represents the Cd content (mg / kg) of the next site, and Cj represents the Cd content (mg / kg) of the previous site; the rice transcriptome sample processing methods are shown in Table 3.

[0094] Table 3 Rice transcriptome sample processing

[0095]

[0096] like Figure 3 As shown, each treatment reduced the Cd translocation capacity of different parts of rice at maturity to varying degrees. Among them, the reduction was more significant in L-nCaO and H-nCaO treatments compared with CK, indicating that the growth regulator of the present invention is more effective in controlling Cd translocation in rice at maturity.

[0097] (3) Subcellular distribution of rice Cd

[0098] Subcellular components were extracted from roots and stems of mature rice samples grown in pots. 0.50 g of the extract was weighed and placed in a pre-cooled mortar at 4°C. 10 ml of pre-cooled extraction solution (containing 250 mmol·L⁻¹ sucrose, 50 mmol·L⁻¹ Tris-HCl-pH 7.5, and 1 mmol·L⁻¹ dithioerythritol) was added, and the mixture was rapidly and thoroughly homogenized. The homogenate was centrifuged at 3000 r / min for 15 min; the precipitate was the cell wall component F1. The supernatant was centrifuged at 12000 r / min for 45 min; the precipitate was the organelle component F2, and the supernatant was the cytoplasmic component F3 (soluble fraction, including cytoplasm and vacuoles). All experimental procedures were performed at 4°C. Each subcellular component sample was transferred to a digestion tube, and 8 mL of a mixture of nitric acid and perchloric acid was added for digestion. The volume was adjusted to 25 mL, and the Cd concentration of each subcellular component in the rice root and stem was determined by ICP-MS.

[0099] like Figure 4 As shown, after applying the regulator of the present invention, the cadmium (Cd) content in all subcellular components of rice roots and stems was significantly lower than that in the control group. This indicates that the regulator of the present invention can effectively reduce the amount of cadmium that enters the cytoplasm and binds to enzymes and organelles (such as mitochondria and nucleus), thereby reducing the toxicity of cadmium to key metabolic organs of rice and ensuring the normal physiological function of cells.

[0100] like Figure 5 As shown, none of the treatments altered the subcellular distribution pattern of Cd in rice rhizomes, but they increased the proportion of Cd in the F1 and F3 components and decreased the proportion of Cd in the F2 component. Furthermore, the organelle components had the lowest Cd content among all components, indicating that this invention can effectively migrate Cd from susceptible organelles to non-toxic fixed sites (such as vacuoles), thereby reducing the biotoxicity of Cd to rice rhizome cells.

[0101] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

[0102] The present invention and its embodiments have been described above. This description is not restrictive, and the accompanying drawings are only one embodiment of the present invention. The actual application is not limited to this. In conclusion, if those skilled in the art are inspired by this description and design similar methods and embodiments without departing from the spirit of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. A growth regulator for controlling cadmium absorption in rice, characterized in that, The growth regulator is prepared from the following raw materials in parts by weight: 68-78 parts calcium oxide nanoparticles, 5-10 parts silicon source, 3-6 parts iron source, 0.5-1.5 parts dispersant, 3-5 parts binder, 3-8 parts carrier, and 0.5-1.5 parts complexing agent; the specific preparation method of the growth regulator is as follows: S1: Dissolve the silicon source in deionized water to prepare a silicate aqueous solution, dissolve the iron source in deionized water to prepare an iron salt aqueous solution, then add a complexing agent to the iron salt aqueous solution and stir until completely dissolved to obtain an iron salt complexed aqueous solution. S2: After adding a dispersant to an aqueous silicate solution, calcium oxide nanoparticles are added, allowing silicate ions to react with the Ca released by the hydrolysis of the calcium oxide nanoparticles. 2+ A reaction occurs to form a composite shell, which is then aged to obtain slurry a; S3: Iron salt complex aqueous solution is added dropwise to slurry a, and OH- is released from slurry a. - Maintain an alkaline environment, then stir the reaction to allow the FeOOH formed in the reaction to be chemically bonded and oriented onto the surface of the composite shell, thus obtaining slurry b; S4: Vacuum dry slurry b, then grind and sieve to obtain composite nanopowder; S5: Add a carrier and binder to the composite nanopowder, mix them evenly, and then granulate to obtain a granule, which is the growth regulator.

2. The growth regulator for controlling cadmium absorption in rice according to claim 1, characterized in that, The silicon source is either potassium silicate or sodium silicate.

3. The growth regulator for controlling cadmium absorption in rice according to claim 1, characterized in that, The iron source is ferric chloride hexahydrate; the dispersant is polyvinylpyrrolidone.

4. The growth regulator for controlling cadmium absorption in rice according to claim 1, characterized in that, The complexing agent is at least one of sodium citrate and sodium tartrate, used to form a stable complex with Fe³⁺ to promote the directional loading of nano-FeOOH.

5. A growth regulator for controlling cadmium absorption in rice according to claim 1, characterized in that, The binder is at least one of carboxymethyl cellulose, starch, and polyvinyl alcohol.

6. A growth regulator for controlling cadmium absorption in rice according to claim 1, characterized in that, The carrier is at least one of diatomaceous earth and bentonite.

7. A growth regulator for controlling cadmium absorption in rice according to claim 1, characterized in that, In step S2, the solid-liquid mass ratio of the calcium oxide nanoparticles to the silicate aqueous solution is 1:2.5-3.5.

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