Magnetite nanoparticle-based plant root-soaking method and application thereof

Abstract

The application discloses a kind of plant root soaking methods based on magnetite nanoparticles and application thereof, belong to the field of agricultural biotechnology.Using magnetite nanoparticles or surface modified magnetite nanoparticles as root soaking treatment agent, short time soaking treatment is carried out on root system in rice seedling stage, so that the nanoparticles form stable adhered "artificial iron film" interface on rice root surface.Rice seedlings treated by root soaking can significantly enhance the adsorption and retention capacity of rice root surface to arsenic under the condition of 0.1~0.5 mg / L arsenic, and reduce the accumulation of arsenic in rice root and leaf by regulating arsenic speciation transformation and inhibiting arsenic related transport process.The application innovatively uses magnetite nanoparticles for root soaking, significantly enhances the adaptability of rice in arsenic environment, and the method is simple and efficient, which has important significance for the application of nanomaterials in crop heavy metal pollution prevention and control.

Description

Technical Field

[0001] This invention belongs to the field of agricultural biotechnology, specifically relating to a plant root soaking method based on magnetite nanoparticles and its application. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Numerous studies have shown that over one-fifth of the world's rice paddies are located in areas with high arsenic content in groundwater. As a typical wetland crop, rice has a strong capacity to absorb and accumulate inorganic arsenic under flooded conditions, making rice a significant source of dietary arsenic exposure for humans. Therefore, reducing arsenic absorption by rice and its translocation to above-ground parts is crucial for ensuring food security.

[0004] Under natural conditions, rice roots typically form an iron-laden structure composed of iron oxides. This structure can, to some extent, inhibit arsenic entry into the plant by adsorbing arsenic and regulating the rhizosphere redox environment. However, in the rice seedling stage, because the iron-laden structure is not yet fully formed, the plant's ability to block arsenic is weak, making it easier for arsenic to enter the root tissue and migrate to the aboveground parts. Current technologies for reducing arsenic absorption in rice mainly include adjusting irrigation methods, applying iron fertilizers, or improving the soil. However, these methods often suffer from slow action, limited ability to regulate the root-surface interface, or a long formation time for the barrier interface, or difficulty in forming a stable barrier interface in the early stages of plant growth. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the purpose of this invention is to provide a plant root soaking method based on magnetite nanoparticles and its application.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows: In a first aspect, the present invention provides a plant root soaking method based on magnetite nanoparticles, the method comprising: The roots of plants are soaked in a root-soaking treatment agent during the seedling stage to allow magnetite nanoparticles to adhere to the root surface and form an arsenic barrier interface. The root-immersion treatment agent includes a magnetite nanoparticle suspension or a surface-modified magnetite nanoparticle suspension.

[0007] Secondly, this invention provides the application of the above-mentioned plant root soaking method based on magnetite nanoparticles in reducing arsenic absorption in rice.

[0008] The application specifically includes at least one: (1) Increase the content of phytochelatin (PC), glutathione (GSH) and abscisic acid (ABA) in plant roots and the content of glutathione (GSH) and abscisic acid (ABA) in plant leaves; (2) It reduces the proportion of trivalent arsenic (As(III)) in total arsenic in plant roots and leaves, and increases the proportion of pentavalent arsenic (As(V)) in total arsenic; (3) Reduce the amount of plant roots OsPHF1 , OsLsi3 and OsLsi6 The amount of expression; (4) Reduce the amount of plant leaves OsLsi3 and OsLsi6 The amount of expression and improvement OsABCC1 The amount of expression.

[0009] Thirdly, the present invention provides a method for reducing arsenic absorption by plants, which employs the above-mentioned plant root soaking method based on magnetite nanoparticles.

[0010] One or more of the above technical solutions have the following advantages or beneficial effects: This invention uses magnetite nanoparticles as a root soaking agent to soak the roots of plants (such as rice) during the seedling stage, so that the nanoparticles form a stable "artificial iron film" interface on the surface of the rice roots.

[0011] Rice seedlings treated with root soaking showed significantly enhanced adsorption and retention capacity of arsenic on the root surface under arsenic concentrations of 0.1-0.5 mg / L. Furthermore, by regulating arsenic speciation and inhibiting arsenic-related transport processes, arsenic accumulation in rice roots and leaves was reduced. This invention innovatively employs magnetite nanoparticle root soaking, significantly enhancing rice's adaptability to arsenic environments. The method is simple and efficient, and holds significant importance for the application of nanomaterials in the control of heavy metal pollution in crops. Attached Figure Description

[0012] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0013] Figure 1 The effects of low and high concentrations of ferrous ions on arsenic accumulation in rice under arsenic stress. Figure 2 These are representative images of rice roots after treatment with magnetite nanoparticles; where A is the control group (CK) and B is Fe3O4 NPs. Figure 3 Scanning electron microscope images of rice root hairs after treatment with magnetite nanoparticles; where A is the control group (CK) and B is Fe3O4 NPs. Figure 4 The effect of magnetite nanoparticle treatment on arsenic accumulation in rice under arsenic stress; Figure 5 The adsorption performance of magnetite nanoparticles on As within 60 minutes; Figure 6 The effects of magnetite nanoparticle treatment on the contents of abscisic acid, chelating agents, and glutathione in rice under arsenic stress were investigated. Among them, A represents the effect on abscisic acid content, B represents the effect on chelating agent content, and C represents the effect on glutathione content. Figure 7 The effects of magnetite nanoparticle treatment on the ratio of trivalent arsenic to total arsenic in rice under arsenic stress are shown in Figure A. A represents the effect of trivalent arsenic to total arsenic in rice, and B represents the effect of pentavalent arsenic to total arsenic. Figure 8 Treatment of rice with magnetite nanoparticles under arsenic stress OsPHF1 , OsLsi3 , OsLsi6 and OsABCC1 The effect of expression; where A is the effect on rice OsPHF1 The effect of expression, B is on rice OsLsi3 The effect of expression, C represents the effect on rice OsLsi6 The effect of expression, D is the effect on rice OsABCC1 The impact of expression; Figure 9 Representative images of rice roots treated with magnetite nanoparticles with different surface modifications are shown. Among them, A is a representative image of rice roots of the CK control group, B is a representative image of rice roots of Fe3O4-CA NPs, and C is a representative image of rice roots of Fe3O4-PAH NPs. Figure 10 for Figure 9 Enlarged view of the framed portion; where (a) is... Figure 9 (b) is an enlarged view of the boxed portion of Figure A. Figure 9 A magnified view of the boxed portion of Figure B, (c) is... Figure 9 An enlarged view of the boxed portion of Figure C in the diagram; Figure 11 Scanning electron microscope images of rice root hairs after treatment with magnetite nanoparticles; where A is the control group (CK), B is Fe3O4-CA NPs, and C is Fe3O4-PAH NPs. Figure 12 Iron content on the surface of rice after treatment with magnetite nanoparticles; Figure 13 The number of nanoparticles on the surface of rice roots after treatment with magnetite nanoparticles. Detailed Implementation

[0014] Terminology Explanation: CK: Control group, i.e., no root soaking treatment agent was used, only pure water was used for root soaking.

[0015] Fe3O4NPs: Iron film formed on the surface of rice roots after treatment with magnetite nanoparticles as a root soaking agent.

[0016] Fe3O4-CA NPs: Surface functionalization modification of magnetite nanoparticles was performed using negatively charged citric acid (CA).

[0017] Fe3O4-PAH NPs: Magnetite nanoparticles were surface functionalized using positively charged polyacrylamide hydrochloride (PAH).

[0018] To address the problem of difficulty in forming a stable barrier interface in the early growth stages of rice plants in existing methods for reducing arsenic absorption, it is of great significance to develop a new method that can rapidly form a stable interface on the rice root surface and inhibit arsenic absorption.

[0019] Magnetite nanoparticles possess high specific surface area, good surface activity, and tunable surface chemistry, making them promising for applications in the adsorption of environmental pollutants and interfacial regulation. Furthermore, root-immersion treatment using nanomaterials allows the materials to act directly on the plant root interface, avoiding the low material utilization efficiency issues associated with traditional foliar spraying or soil application.

[0020] This invention develops a method for treating rice roots using magnetite nanoparticles. The nanoparticles form a stable interface on the rice root surface, thereby enhancing the root surface's adsorption and retention capacity for arsenic and reducing arsenic migration into the plant. Combined with the low cost and simplicity of the root soaking process, using magnetite nanoparticles for root soaking has the potential to become an environmentally friendly, cost-effective, and farmer-friendly method for promoting crop growth under adverse environmental conditions.

[0021] Using magnetite nanoparticles as a root-soaking agent, a dense "artificial iron film" formed on the surface of rice roots after root soaking. The adsorption performance of the magnetite nanoparticles was measured, and rice seedlings grown in an arsenic environment for 7 days were harvested and their total arsenic content, phytochelatin (PC) content, glutathione (GSH) content, abscisic acid (ABA) content, trivalent arsenic ratio, and pentavalent arsenic ratio were determined. OsPHF1 , OsLsi3 , OsLsi6 and OsABCC1 The root immersion treatment of this invention can form a stable interface on the rice root surface and effectively reduce arsenic absorption, improve stress signal sensing ability and intracellular heavy metal chelation ability. It has good application prospects.

[0022] A first typical embodiment of the present invention provides a plant root soaking method based on magnetite nanoparticles. The method includes: soaking the roots of plants in a magnetite nanoparticle suspension during the seedling stage to allow the nanoparticles to adhere to the plant root surface and form an arsenic barrier interface.

[0023] In one or more embodiments, the plant includes rice. The plant (such as rice) is cultivated hydroponically under conditions including 16 hours of light / 8 hours of darkness and a temperature of 25–27 °C.

[0024] In one or more embodiments, before hydroponics, the plant seeds are induced. Specifically, sterilized seeds are soaked in clean water at 25-30°C for 20-24 hours. After soaking, the seeds are rinsed with sterile water to obtain induced seeds.

[0025] In one or more embodiments, the plant (such as rice) seedlings are three-week-old or four-week-old seedlings.

[0026] In one or more embodiments, the magnetite nanoparticles are Fe3O4 nanoparticles with a particle size of 100-500 nm, preferably 115-120 nm. The magnetite nanoparticles can be synthesized using a conventional thermal decomposition method.

[0027] To obtain magnetite nanoparticles with superior adhesion performance on rice root surfaces, the surface of the magnetite nanoparticles was functionalized and modified. The surface-modifying groups included at least one of positively charged polyacrylamide hydrochloride (PAH) and negatively charged citric acid (CA), with positively charged PAH being preferred. PAH-modified magnetite nanoparticles showed significantly higher adhesion to the root surface than citric acid-modified materials, and were mainly concentrated in the root hair region, exhibiting stronger interfacial bonding ability. Furthermore, the mass ratio of the surface-modifying groups to the magnetite nanoparticles was (0.8~1.2):(0.8~1.2), preferably 1:1.

[0028] In one or more embodiments, magnetite nanoparticles are formulated into a suspension and ultrasonically dispersed, and then the entire root system of plant seedlings is immersed in the suspension for treatment.

[0029] In one or more embodiments, the concentration of magnetite nanoparticles is 0.5~5 g / L, specifically 0.5 g / L, 1 g / L, 2 g / L, 3 g / L, 4 g / L, 5 g / L, etc., preferably 0.5~1.5 g / L, and most preferably 1 g / L.

[0030] In one or more embodiments, the soaking time is 2 to 10 minutes, specifically 2 minutes, 3 minutes, 4 minutes, 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes, 10 minutes, etc., preferably 4 to 6 minutes, and most preferably 5 minutes.

[0031] Compared to existing technologies that use ferrous ions to induce the formation of natural iron films, this invention uses magnetite nanoparticles as a root-soaking treatment agent, which can construct a stable iron film structure on the surface of rice roots in a short time, thereby effectively blocking the absorption of arsenic. Comparative experiments show that ferrous ions are difficult to form an iron film with significant blocking effect under three-day soaking treatment conditions, and have no significant effect on blocking arsenic. Figure 1 The method of this invention can achieve a highly efficient arsenic barrier effect without relying on a long-term oxidation process in the rhizosphere, and has significant time and application advantages.

[0032] In one or more embodiments, the method further includes: cleaning the root system and then transferring the soaked plant to a nutrient solution containing arsenic for cultivation. The cultivation can be carried out in an artificial incubator, and the cultivation conditions are: temperature of 20~30℃, preferably 28℃, and humidity of 45~55%, preferably 50%.

[0033] In one or more embodiments, the concentration of arsenic in the nutrient solution containing arsenic is 0.1~0.5 mg / L, specifically 0.1 mg / L, 0.2 mg / L, 0.3 mg / L, 0.4 mg / L, 0.5 mg / L, etc.

[0034] Preferably, the root soaking treatment of the rice seedlings specifically includes the following steps: S1: Germinate rice seeds and cultivate them to the seedling stage; S2: Magnetite nanoparticles were prepared into a suspension and ultrasonically dispersed, and then the roots of rice seedlings were completely immersed in the suspension for treatment. S3: After soaking, rinse the roots with deionized water to remove any loosely attached nanoparticles, and then transfer the treated rice seedlings back into the nutrient solution for continued cultivation.

[0035] This application innovatively uses magnetite nanoparticles to treat rice roots, which greatly improves the rice's ability to cope with arsenic stress and is easy to operate and the procedure is standardized.

[0036] A second typical embodiment of the present invention provides the application of the above-mentioned plant root soaking method based on magnetite nanoparticles in reducing arsenic absorption in rice.

[0037] Furthermore, the application specifically includes at least one: (1) Increase the content of phytochelatin (PC), glutathione (GSH) and abscisic acid (ABA) in plant roots and the content of glutathione (GSH) and abscisic acid (ABA) in plant leaves; (2) It reduces the proportion of trivalent arsenic (As(III)) in total arsenic in plant roots and leaves, and increases the proportion of pentavalent arsenic (As(V)) in total arsenic; (3) Reduce the amount of plant roots OsPHF1 , OsLsi3 and OsLsi6 The amount of expression; (4) Reduce the amount of plant leaves OsLsi3 and OsLsi6 The amount of expression and improvement OsABCC1 The amount of expression.

[0038] A third typical embodiment of the present invention provides a method for reducing arsenic absorption by plants, which employs the above-mentioned plant root soaking method based on magnetite nanoparticles.

[0039] In this invention, unless otherwise specified, all other test materials and instruments are conventional test materials in the field and can be purchased through commercial channels.

[0040] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0041] Example 1 1. Seeds and materials The rice seeds used in the experiment were of variety 93-11. The magnetite nanoparticles used in the experiment were synthesized by thermal decomposition and had a particle size of approximately 115 nm.

[0042] 2. Root soaking treatment conditions The rice seedlings used for root soaking were 3-4 week old. The soaking time was 5 minutes, and the soaking temperature was 28℃. The concentration of the magnetite nanoparticle solution was 1 g / L, and it was essential to ensure that the rice roots were completely submerged in the solution.

[0043] 3. Root soaking treatment process Rice cultivation: Select 10 g of plump and uniformly sized rice seeds and disinfect them with 75% alcohol for 5 minutes, then rinse them thoroughly with sterile water. Finally, soak the rice seeds in clean water at 28℃ for 24 hours. After soaking, rinse the rice seeds thoroughly with sterile water to obtain induced rice seeds, which are then transferred to a hydroponic system for cultivation. The cultivation conditions are: temperature: 25-27℃, photoperiod: 16 h light / 8 h dark. Seedlings are cultivated to 3-4 weeks of age for later use.

[0044] Root immersion treatment: The magnetite nanoparticle solution was prepared into a nano-suspension with a concentration of 1 g / L and ultrasonically dispersed. The roots of rice seedlings were completely immersed in the nanoparticle suspension for 5 min. After treatment, the roots were rinsed with deionized water and transferred to a nutrient solution containing 0.1 mg / L arsenic for cultivation.

[0045] Characterization of rice roots and determination of adsorption performance of magnetite nanoparticles: Rice samples from the control group and after root soaking were photographed and analyzed using scanning electron microscopy. Magnetite nanoparticles were also used for a 60-minute arsenic adsorption experiment.

[0046] Arsenic stress experiment: After seven days of growth, rice was harvested and the total arsenic content, phytochelatin (PC) content, glutathione (GSH) content, abscisic acid (ABA) content, trivalent arsenic ratio, and pentavalent arsenic ratio were measured in the roots and leaves. OsPHF1 , OsLsi3 , OsLsi6 and OsABCC1 The amount of expression.

[0047] 4. Experimental Results pass Figure 2 It can be seen that after root soaking, a dense, black "artificial iron film" forms on the surface of rice roots. Through... Figure 2 Scanning electron microscopy images of rice root hairs show that magnetite nanoparticles are evenly distributed on the surface of the rice after root soaking. Through... Figure 4 It was found that, under arsenic conditions, compared to the control group (root soaking in pure water), root soaking reduced the arsenic content in rice roots and leaves by 50% and 41.4%, respectively. Simultaneously, root soaking increased the arsenic content on the root surface by 64.4%. Figure 5 The results show that the adsorption rate of As(V) by magnetite nanoparticles reached 36.1% within 60 min. These results indicate that root soaking treatment forms an artificial arsenic adsorption interface on the surface of rice roots, thereby blocking arsenic on the rice root surface and reducing the absorption of arsenic by rice.

[0048] pass Figure 6 The results showed that, under arsenic conditions, compared with the control group, root soaking treatment increased the contents of phytochelatin (PC), glutathione (GSH), and abscisic acid (ABA) in rice roots by 19.02%, 16.39%, and 23.18%, respectively. Furthermore, the contents of glutathione (GSH) and abscisic acid (ABA) in leaves increased by 21.96% and 42.98%, respectively. These results indicate that root soaking treatment enhances the rice's ability to sense stress signals and its intracellular heavy metal chelation capacity.

[0049] pass Figure 7It can be seen that, under arsenic conditions, compared with the control group, root soaking treatment reduced the proportion of trivalent arsenic (As(III)) in total arsenic in rice roots and leaves by 41.78% and 7.67%, respectively, while increasing the proportion of pentavalent arsenic (As(V)) in total arsenic by 41.78% and 7.67%, respectively. Since As(III) has a stronger migration ability in rice, root soaking reduces the migration ability of arsenic in rice by reducing the proportion of As(III).

[0050] pass Figure 8 It can be seen that, under arsenic conditions, compared to the control group, root soaking treatment reduced the levels of arsenic in rice roots. OsPHF1 , OsLsi3 and OsLsi6 The expression levels decreased by 35.91%, 24.24%, and 35.77%, respectively. Furthermore, in leaves... OsLsi3 and OsLsi6 The expression levels decreased by 34.55% and 45.72%, OsABCC1 The expression level increased by 92.38%. These results indicate that root soaking treatment can downregulate genes related to As(V) absorption and As(III) transport, while upregulating genes related to arsenic chelation and vacuolar isolation, thereby helping to reduce the absorption and transport of arsenic in rice.

[0051] In summary, after root soaking treatment, a dense "artificial iron film" forms on the surface of the rice roots. This was achieved by measuring the adsorption properties of magnetite nanoparticles and harvesting rice seedlings grown in an arsenic environment for 7 days, and then measuring their total arsenic content, phytochelatin (PC) content, glutathione (GSH) content, abscisic acid (ABA) content, trivalent arsenic ratio, and pentavalent arsenic ratio. OsPHF1 , OsLsi3 , OsLsi6 and OsABCC1 The root soaking treatment of this invention can form a stable interface on the rice root surface and effectively reduce arsenic absorption, improve the ability to sense stress signals and the ability to chelate heavy metals in cells, and has good application prospects.

[0052] Example 2 Unlike Example 1, to obtain magnetite nanoparticles with better adhesion performance on rice roots, the surface of the magnetite nanoparticles was functionalized, and different surface modification methods were screened and compared. Specifically, positively charged polyacrylamide hydrochloride (PAH) and negatively charged citric acid (CA) were used to functionalize the surface of the magnetite nanoparticles (surface modification group: nanomaterial = 1:1 (m / m)), respectively, to obtain two nanomaterials: Fe3O4-PAH NPs and Fe3O4-CANPs.

[0053] The adhesion behavior of nanoparticles on the surface of rice roots was characterized by root soaking treatment, and it was found that ( Figures 9 to 13The adhesion amount of PAH-modified magnetite nanoparticles on the root surface was significantly higher than that of CA-modified magnetite nanomaterials, and they were mainly enriched in the root hair region, exhibiting stronger interfacial bonding ability. Furthermore, quantitative analysis of the iron content on the root surface and statistical analysis of the number of nanoparticles attached both showed that the loading of Fe3O4-PAH NPs on the root surface was significantly increased. Based on the above experimental results, PAH-modified magnetite nanoparticles are preferred as the root impregnation agent to achieve a more efficient and stable root surface assembly effect.

[0054] In the experiments described above, all nanoparticles without specific designations were PAH-modified magnetite nanoparticles.

[0055] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A magnetite nanoparticle-based plant root-dipping method, characterized by, The method includes: soaking the roots of plants in a root-soaking treatment agent during the seedling stage to allow magnetite nanoparticles to adhere to the plant root surface and form an arsenic barrier interface. The root-impregnation treatment agent is a magnetite nanoparticle suspension or a magnetite nanoparticle suspension modified with surface groups. Soaking time is 2-10 minutes; The modified surface groups are positively charged polyacrylamide hydrochloride; The mass ratio of modified surface groups to magnetite nanoparticles was (0.8~1.2):(0.8~1.2); The magnetite nanoparticles are Fe3O4 nanoparticles with a particle size of 100~500nm; the concentration of the root-impregnation treatment agent is 0.5~5g / L; The plant in question is rice.

2. The plant root dipping method according to claim 1, wherein The plants were cultivated hydroponically under the following conditions: 14-17 h of light / 6-8 h of darkness, and a temperature of 25-27 ℃. The plant seedlings are three or four weeks old.

3. The application of the plant root soaking method based on magnetite nanoparticles as described in any one of claims 1 to 2 in reducing plant arsenic absorption; wherein the plant is rice.

4. A method of reducing arsenic uptake by a plant, comprising, The plant root soaking method based on magnetite nanoparticles as described in any one of claims 1 to 2 is adopted; the plant is rice.

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