Application of manganese ferrite nanomaterial in enhancing drought resistance of rice

Abstract

The application discloses application of manganese ferrite nanomaterial in enhancing drought resistance of rice, and belongs to the technical field of novel pesticides.The application of the manganese ferrite nanomaterial in enhancing drought resistance of rice is that soil and the manganese ferrite nanomaterial are mixed uniformly to form mixed soil, and then rice seeds are planted for cultivation; the concentration of the manganese ferrite nanomaterial in the soil is 1-50 mg / kg, and is preferably 10 mg / kg; the manganese ferrite nanomaterial is spherical, the particle size is 20-60 nm, the hydrodynamic diameter is 982 nm, and the Zeta potential is-27 mV.The application can effectively promote the growth and drought resistance of rice under drought stress, and significantly improves the yield and quality of rice under drought stress.

Description

TECHNICAL FIELD

[0001] The application relates to application of manganese ferrite nanomaterial in enhancing drought resistance of rice, and belongs to the technical field of novel pesticides. BACKGROUND

[0002] With the rapid growth of global population, it is predicted that the global demand for food will increase by 60-70% by 2050. The current food production is far from meeting the future demand. With climate change, rainfall reduction, and intensified transpiration, the global drought problem is becoming increasingly serious. Therefore, effectively improving the yield of crops under drought stress is one of the methods to ensure the sustainable increase of global food production. However, the agricultural irrigation water required by traditional agricultural technology cannot support the water required to alleviate large-scale high-intensity drought. Under the imminent problem of world food security, nano-agricultural technology has emerged as the times require.

[0003] With the development of nanotechnology, nanomaterials have shown great application potential in controlling crop diseases due to their unique physical and chemical properties (nanosize, bioavailability, etc.). However, current research on nanomaterials resisting drought stress after application mainly focuses on zinc and silicon-based nanomaterials, and less on iron and titanium-based nanomaterials. Compared with zinc and silicon-based nanomaterials, iron-based nanomaterials not only enhance the activity of various ROS scavenging enzymes in plants under drought stress, but also increase the content of substances such as proline and glycine betaine that maintain osmotic homeostasis. At the same time, iron, as the central element of plant photosynthetic pigments, also plays a crucial role in plant photosynthesis. Manganese, as a key coenzyme factor in plants, can promote carbohydrate metabolism and nitrogen metabolism and enhance the bioavailability of phosphorus and calcium, and as an electron donor in plant photosystem II, it enhances the intensity of photosynthesis.

[0004] At present, CN 114586614 A discloses application of manganese ferrite nanomaterial in inducing early flowering and yield increase of tomatoes. However, rice and tomatoes belong to completely different crops, and there is no correlation between early flowering and yield increase and drought resistance. Therefore, whether manganese and iron combined can exhibit better effect of enhancing the resistance of rice to drought stress? What is the optimal concentration of manganese ferrite nanomaterial for enhancing the drought resistance of rice? Can it improve the yield of rice under drought? It is not known. SUMMARY

[0005] [TECHNICAL PROBLEM]

[0006] At present, there is no literature disclosing that manganese ferrite nanomaterial can be used for rice, nor that it can be used for drought resistance of rice.

[0007] [TECHNICAL SCHEME]

[0008] In order to solve the above problems, the application uses manganese ferrite nanomaterials for rice to enhance its drought resistance performance, and obtains the optimal concentration of manganese ferrite nanomaterials and the molecular mechanism of manganese ferrite nanomaterials for rice drought resistance.

[0009] The first object of the application is to provide the application of manganese ferrite nanomaterials in enhancing the drought resistance performance of rice, wherein the application is to mix the soil and manganese ferrite nanomaterials uniformly to form mixed soil, and then plant rice seeds for cultivation.

[0010] In an embodiment of the application, the concentration of the manganese ferrite nanomaterials in the soil is 1-50 mg / kg, and is further preferably 10 mg / kg.

[0011] In an embodiment of the application, the Fe and Mn ions in the manganese ferrite nanomaterials are mostly in the 2+ valence state, and the Mn 2+ content (87.3%) is greater than the Mn 3+ content (12.7%), the Fe 2+ content (67.4%) is higher than the Fe 3+ content (32.6%), which can slowly release Mn and Fe ions.

[0012] In an embodiment of the application, the manganese ferrite nanomaterials are spherical, the particle size is 20-60 nm, the hydrodynamic diameter is 982 nm, and the Zeta potential is -27 mV.

[0013] In an embodiment of the application, 1-3 rice seeds are planted in 1.5 kg of soil.

[0014] In an embodiment of the application, the preparation method of the manganese ferrite nanomaterials comprises the following steps:

[0015] MnCl2·4H2O and FeCl3·6H2O are stirred in (CH2OH)2 until completely dissolved to obtain a mixed solution of manganese ions and iron ions;

[0016] NaOH is dissolved in water to obtain a NaOH solution;

[0017] The NaOH solution is added to the mixed solution at a speed of one drop per 5 s, and red-brown suspended particles are gradually formed in the solution until the pH reaches 11; after sufficient stirring, the precipitate is transferred to a teflon-lined reaction kettle, heated at 200°C for 12 h, cooled after removal, and finally vacuum freeze-dried to obtain manganese ferrite nanomaterials (MnFe2O4 nanomaterial powder);

[0018] The concentration of manganese ions and iron ions in the mixed solution is 0.5 mol / L and 1 mol / L respectively; and the concentration of the NaOH solution is 5 mol / L.

[0019] A second object of the application is a method for improving photosynthesis and increasing the content of nutrient elements of rice under drought, which comprises the steps of mixing the soil and the manganese ferrite nanomaterial to form a mixed soil, and then planting rice seeds for cultivation; wherein the concentration of the manganese ferrite nanomaterial in the soil is 1-50 mg / kg; the manganese ferrite nanomaterial is spherical, with a particle size of 20-60 nm, a hydrodynamic diameter of 982 nm, and a Zeta potential of -27 mV; and the nutrient elements include phosphorus (P), potassium (K), magnesium (Mg), and sulfide (S).

[0020] A third object of the application is to provide a method for improving the drought resistance of rice by increasing the response intensity of rice to drought, increasing the proline content and reducing the malondialdehyde content of leaves, and increasing the root angle, which comprises the steps of mixing the soil and the manganese ferrite nanomaterial to form a mixed soil, and then planting rice seeds for cultivation; wherein the concentration of the manganese ferrite nanomaterial in the soil is 1-50 mg / kg; the manganese ferrite nanomaterial is spherical, with a particle size of 20-60 nm, a hydrodynamic diameter of 982 nm, and a Zeta potential of -27 mV.

[0021] [Advantages]

[0022] (1) The manganese ferrite nanomaterial can effectively promote the growth and drought resistance of rice under drought stress. -1 Under the treatment of 1 mg kg -1 and 10 mg kg -1 of the manganese ferrite nanomaterial, the aboveground biomass of rice increased significantly by 77.2% and 70.3% compared with the drought treatment; under the treatment of 10 mg kg -1 of the manganese ferrite nanomaterial, the intercellular CO2 concentration and net photosynthetic rate increased by 26.9% and 23.1%, respectively; the total photosynthetic pigment and carotenoid content of rice increased significantly by 10.9% and 26.4%, respectively; the contents of phosphorus (P), potassium (K), magnesium (Mg), and sulfide (S) increased significantly by 14.1%, 26.5%, 46.0%, and 19.8%, respectively; the contents of phosphorus (P) and sulfur (S) in the roots increased significantly by 27.2% and 49.8%, respectively; the expression levels of CLE25 gene and response gene NCED3, the ABA content, and the proline content were significantly increased, and the malondialdehyde content was significantly reduced.

[0023] (2) Soil application of 10 mg / kg of manganese ferrite nanomaterial significantly improved the yield and quality of rice under drought stress; among them, compared with the control (CK) and equivalent ions (Ion) under severe drought (field moisture capacity FMC = 30%), the grain filling rate increased by 61.1% and 46.7%, respectively. The thousand-grain weight, grain number and panicle length were increased by 22.5%, 19.6% and 41.3% compared with the control (CK) under severe drought (field moisture capacity FMC = 30%). The Ca, P, Fe, Mn and K elements in the grain increased by 135.1%, 21.2%, 43.6%, 31.1% and 19.3%, respectively. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 Performance characterization of manganese ferrite (MnFe2O4) nanomaterial prepared in Example 1; wherein (A) TEM image; (B) XRD image; (C) Fe 2p orbital XPS image; (D) Mn 2p orbital XPS image.

[0025] Figure 2 Effect of different concentrations of MnFe2O4nanomaterial on rice growth under drought stress; wherein (A) growth phenotype; (B) biomass; (C) intercellular CO2concentration; (D) net photosynthetic rate; (E) total photosynthetic pigment in leaves; (F) carotenoid content in leaves; (G) polysaccharide content in shoots; (H) root polysaccharide content.

[0026] Figure 3 Different concentrations of MnFe2O4nanomaterials enhance the signal response of rice under drought stress; wherein (A) CLE25 gene relative expression; (B) NCED3 gene relative expression; (C) ABA content in leaves; (D) proline content; (E) malondialdehyde (MDA) content.

[0027] Figure 4 Different concentrations of MnFe2O4nanomaterials promote rice root development; wherein (A) root angle photo; (B) root angle; (C) IAA concentration.

[0028] Figure 5 Different concentrations of MnFe2O4nanomaterials change the expression of genes related to root angle control in rice; wherein (A) PIN gene family expression intensity; (B) OR1 gene expression; (C) AUX gene family expression intensity; (D) DRO1 gene expression.

[0029] Figure 6 10 mg kg -1The yield and quality of rice treated with MnFe2O4 nanomaterials and comparative examples 1-3; among which, (A) rice panicle; (B) grain filling rate; (C) thousand-grain weight; (D) number of grains; (E) panicle length; (F) gluten content; (G) Ca, P, S, Fe content; (H) Mg, Zn, Mn, K content. Detailed Implementation

[0030] The preferred embodiments of the present invention are described below. It should be understood that the embodiments are for better explanation of the present invention and are not intended to limit the present invention.

[0031] Test method:

[0032] 1. TEM test:

[0033] Manganese ferrite nanomaterials were prepared into a suspension and thoroughly dispersed by ultrasonication for 30 minutes. A drop of the solution was then pipetted onto a 200-mesh copper grid and allowed to air dry naturally. The morphology and particle size of the material were then characterized using a transmission electron microscope (TEM, JEM-2100, Japan).

[0034] 2. Hydraulic diameter distribution test:

[0035] The hydraulic diameter and zeta potential of manganese ferrite nanomaterials in deionized water were determined using a Malvern nanoparticle size analyzer (Nano-ZS90, Malvern Instruments, UK).

[0036] 3. XRD test:

[0037] Peak detection and matching were performed using X-ray diffraction (XRD, Bruker AXS, Germany) and Jade 5.0 software.

[0038] 4. XPS test:

[0039] X-ray photoelectron spectroscopy (XPS, ThermoScientific ESCALAB250Xi, USA) was used to analyze the valence state changes of Fe and Mn.

[0040] 5. Fresh weight test:

[0041] Cut off the above-ground parts of the rice and weigh them to obtain the above-ground fresh biomass; carefully remove the roots from the pot, wash off the surface soil with tap water, dry them with paper towels, and weigh them to obtain the underground fresh biomass.

[0042] 6. Dry weight test:

[0043] Open the oven and preheat the temperature to 100-105℃; put the weighed fresh plant parts above and below ground into paper bags and place them in the oven, blanch at 100-105℃ for 10 minutes, then lower the oven temperature to about 70-80℃ and dry until constant weight; weigh.

[0044] 7. Intercellular CO2 concentration:

[0045] Under drought conditions, photosynthesis was measured in situ on the second fully expanded leaf of rice using a handheld photosynthesis measurement system (CIRAS-3, PP-Systems, USA). Measurements were taken from 8:00 AM to 10:00 AM, with a CO2 concentration of 400 μmol·mol⁻¹. -1 The light intensity is 1000 μmol·m -2 ·s -1 The minimum stabilization time is 120 seconds.

[0046] 8. Net photosynthetic rate:

[0047] The photosynthetic parameters of the second-to-last leaves were measured using a portable photosynthesis measurement system (CIRAS-3) from 9:30 AM to 11:00 AM. The light intensity was set to 1000 μmol / (m²). 2 The temperature was 28℃ and the relative humidity was 50.5%. Five plants were selected from each treatment group for measurement. Data were recorded after the readings stabilized (approximately 36 minutes).

[0048] 9. Tests for total photosynthetic pigments and carotenoids in leaves:

[0049] 40 mg of fresh rice leaf tissue was collected and pulverized in 4 mL of 80% acetone. The pulverized tissue was then placed in a constant temperature water bath at 68°C for 15 min. After removal, the tissue was centrifuged at 4000 rpm for 15 min. The supernatant was collected, and the absorbance of the sample was measured at 663 nm, 646 nm, and 470 nm. Chlorophyll a (Ca = 12.21A) was calculated. 663 -2.81A 646 ); Chlorophyll b (Cb=20.13A) 646 -5.03A 663 ) and carotenoids (Cx+c=[1000A) 470 -3.27Ca-104Cb] / 229) content. Among them, the chlorophyll content is calculated as (color concentration (mg·L) -1 The conversion is calculated as follows: (1) × liquid volume (L) × dilution factor / sample fresh weight (g).

[0050] 10. Polysaccharide content (aerial parts and roots):

[0051] Weigh 10 mg of anhydrous glucose, add to a 50 mL volumetric flask and dissolve with ultrapure water, then weigh 5 g of phenol into 100 mL of ultrapure water and shake until the phenol is completely dissolved. Take 200 mg of fresh plant sample into a test tube, add 10 mL of ultrapure water, and place the test tube in a boiling water bath for 15 min, then filter with filter paper and treat to 100 mL in a volumetric flask and dilute to the mark with ultrapure water. Finally, weigh 1 mL of glucose standard sample liquid into a test tube, then add 2 mL of 5% phenol solution and 5 mL of concentrated sulfuric acid in sequence, stand for 30 min, then cool the test tube to room temperature, and take the reacted solution and measure the absorbance value at 450 nm on an enzyme marker.

[0052] 11. Test of nutrient elements:

[0053] Grind about 25 mg of completely dried above-ground tissue samples and root system samples of rice with a ceramic mortar and place them in a digestion tube, then add 3 mL of concentrated nitric acid and 3 mL of ultrapure water; then digest the mixture in a digestion instrument (MARS 6, CEM, Matthews, NC, USA) with a program set at 190°C and 1400W. After digestion is completed, filter the liquid through a 0.22 μm water filter membrane, then dilute and dilute to volume with ultrapure water. The content of elements in different tissues (above-ground and root) is detected by inductively coupled plasma mass spectrometry (ICPMS, iCAP-TQ, ThermoFisher, Germany).

[0054] 12. Test of relative expression amount of genes:

[0055] Corresponding primers are provided by Sangon Biotech Co., Ltd. (Shanghai, China). The total RNA extraction method in different tissues refers to the instructions of the plant RNA extraction kit (TaKaRa MiniBEST RNA Extraction Kit, Japan). The RNA reverse transcription system is performed according to the instructions of the EasyQuick RT MasterMix kit (CWBIO, China). The fluorescence quantitative amplification reaction system refers to the guidelines of the UltraSYBR Mixture kit (CWBIO, China), and after the amplification reaction system is added, the subsequent operation is performed on the CFX96 Real-Time system platform (Bio-Rad, USA). Each gene is set with 6 parallels, and OsUbi gene is used as the internal reference gene. After the amplification reaction is completed, the Ct value of the measured experimental results is quantitatively determined by 2 -ΔΔCt method.

[0056] 13. Test of ABA, proline content, and malondialdehyde content:

[0057] (1) ABA: The sample was kept in -80℃ refrigerator, and grinded in liquid nitrogen until completely pulverized, then 1 mL ethyl acetate (containing 10 μg·mL -1 BHT - butylated hydroxyl toluene); vortex mixed for 15 min, and ultrasonicated for 15 min in ice bath; then centrifuged at 4℃, 13000 rpm for 10 min, the supernatant (recorded amount) was transferred to a new centrifuge tube, and after gently nitrogen blowing dry, 200 μL 70% methanol was added for re-dissolution; after vortex mixed for 5 min again, ultrasonicated for 5 min in ice bath, and then centrifuged at 4℃, 12000 rpm for 10 min. Finally, 100 μL supernatant was carefully taken into a sample bottle, and the hormone content in the sample was determined by LC-MSMS.

[0058] The liquid phase parameters were set as follows: mobile phase A: 0.01% formic acid water, mobile phase B: 0.01% formic acid acetonitrile.

[0059] The elution program is shown in Table 1:

[0060] Table 1

[0061] Time (min) B(％) 0 5 1.5 5 9 70 10 70 10.1 5 15 5

[0062] The chromatographic column was Waters HSS T3 1.8 μm 2.1 x 100 mm. The flow rate was set to 0.35 mL·min -1 , and the column temperature was 35℃.

[0063] (2) Proline: 50 mg sample was grinded in liquid nitrogen, then 10 mL 3% sulfosalicylic acid was added, and after the proline in the sample was fully extracted, the mixture was filtered. 2 mL filtrate, 2 mL glacial acetic acid and 2 mL ninhydrin solution (1.25 g ninhydrin was weighed and dissolved in 20 mL 6 mol·L -1 phosphoric acid solution and 30 mL glacial acetic acid) were fully mixed, and the mixture was placed in a boiling water bath for 1 h of full reaction. After the water bath, 4 mL toluene was added to the reaction mixture and mixed vigorously for 30 s. The chromophore containing toluene was extracted from the aqueous phase, the absorbance value at 520 nm was read in the enzyme marker instrument, and the proline content in the sample was calculated by comparing the standard curve.

[0064] (3) Malondialdehyde (MDA): Take fresh plant tissue sample about 200 mg, placed in a mortar, measured 5 mL of distilled water, first take 2 mL of distilled water to grind to homogenate and then transfer to 10 mL range of centrifuge tube, then use the remaining 3 mL of distilled water to rinse the mortar three times, add the grinding liquid in the centrifuge tube to 5 mL scale. Then add 5 mL of 0.5% thiobarbituric acid (TBA) to each centrifuge tube (weigh 0.5 g of thiobarbituric acid solid, dissolved in 20% trichloroacetic acid and constant volume to 100 mL), so that each centrifuge tube reaches 10 mL of mixture. Then cover the centrifuge tube and place it in a boiling water bath for 10 min, cool to room temperature, centrifuge at 1000 rpm for 10 min. Measure the absorbance at 450 nm, 532 nm and 600 nm respectively, and calculate the MDA content in the extract according to C (pmol·g -1 ) = [6.452 (A 532 -A 600 ) -0.56A 450 ] × V T / (V0×W); wherein V0: the measured volume; V T : the total volume of the extract; W: the fresh weight of the plant tissue.

[0065] 14. Test of rice yield and quality:

[0066] (1) Albumin content determination:

[0067] After the safe maturity of the rice, the grains are dehulled and ground into powder under liquid nitrogen. Take 0.1 g of rice powder in a 1.5 mL centrifuge tube and add 1 mL of distilled water (dH2O). Shake at room temperature for 10 min to completely mix and extract. Then centrifuge at 12000 rpm for 20 min at 4°C and collect the supernatant. Repeat the extraction step 3 times.

[0068] Prepare the Coomassie Brilliant Blue G-250 staining working solution: weigh 10 mg of Coomassie Brilliant Blue G-250 powder and completely dissolve it in 5 mL of 95% ethanol. Add the mixture to 10 mL of 85% phosphoric acid, stirring while adding. Then dilute with distilled water to 100 mL scale. Filter the working solution with filter paper and store it in a brown reagent bottle in the dark.

[0069] Prepare the standard bovine serum albumin (BSA) solution: weigh 4.0 mg of BSA powder and dissolve it in 1 mL of 0.15 mol·L -1 NaCl solution. At this time, the concentration of the BSA standard protein solution in the mixture is 4 mg·mL -1 . Store it in a -20°C refrigerator.

[0070] In 200 μL microcentrifuge tube, 30 μL 4000 μg·mg -1 of BSA standard protein solution was accurately pipetted, 30 μL distilled water was added, and 2000 μg·mg -1 of BSA solution was obtained, and the above steps were repeated to obtain 2000, 1000, 500, 250, 125, 62.5, 31.25, 15.625 μg·mL -1 of BSA solution by serial dilution. A new 200 μL microcentrifuge tube was prepared, 3 μL of each different concentration of serial dilution was taken, and 297 μL of Coomassie brilliant blue G-250 staining working solution was mixed uniformly in the centrifuge tube, and the reaction was allowed to proceed at room temperature for 2 min, and 200 μL of the reaction solution was taken into the enzyme-labeled plate, and the absorbance value at 595 nm wavelength was measured, and the content of albumin in the sample was calculated.

[0071] (2) Globulin content determination:

[0072] After grinding the rice powder in liquid nitrogen, 1 mL of 0.5M NaCl extraction solution (1.461g NaCl dissolved in 50mL deionized water) and 10mM Tris-HCl (121.14mg dissolved in 100mL deionized water, 0.1M-438.6μL concentrated hydrochloric acid dissolved in 50mL deionized water, and the pH was adjusted to 6.8 with HCl) were added, and the mixture was shaken and mixed at 37°C for 10 min, and then centrifuged at 4°C and 12000 rpm for 20 min to collect the supernatant, and the above process was repeated 3 times, and the protein content was determined according to (1).

[0073] (3) Alcohol-soluble protein content determination

[0074] After grinding the rice powder in liquid nitrogen, 70% alcohol was added to extract the alcohol-soluble protein, and then centrifuged at 4°C and 12000 rpm for 20 min to collect the supernatant, and the above process was repeated 3 times, and the protein content was determined according to (1).

[0075] (4) Gluten content determination

[0076] After grinding the rice powder in liquid nitrogen, 1% lactic acid was added to extract the gluten, and then centrifuged at 4°C and 12000 rpm for 20 min to collect the supernatant, and the above process was repeated 3 times, and the protein content was determined according to (1).

[0077] Raw materials used in the examples:

[0078] Rice seeds were purchased from (Chuangliangyou 669) from Anhui Lvyi Seed Co., Ltd., which is a branch of indica two-line hybrid rice.

[0079] The size of the flowerpot is 120mm in diameter x 178mm in height.

[0080] Soil samples were collected from a farm in Mashan (120°15'E, 31°54'N). The total nitrogen, total organic carbon and pH in the soil were 47.7 g / kg, 119.7 g / kg and 6.8, respectively.

[0081] In the examples, the soil moisture content was controlled at 100% during normal cultivation (without drought stress) and at 30% during drought stress.

[0082] Example 1

[0083] The preparation method of manganese ferrite nanomaterials includes the following steps:

[0084] 1.984 g of MnCl2·4H2O and 5.4 g of FeCl3·6H2O were stirred in 20 mL of (CH2OH)2 at 24 °C until completely dissolved to obtain a mixed solution with manganese ions of 0.5 mol / L and iron ions of 1 mol / L.

[0085] Dissolve 8.0 g of NaOH in 40 mL of water to obtain a 5 mol / L NaOH solution;

[0086] NaOH solution was added to the mixed solution at a rate of one drop every 5 seconds, and reddish-brown suspended particles gradually formed in the solution until the pH reached 11. After stirring thoroughly for 10 minutes, in order to obtain nano-sized MnFe2O4 particles, the precipitate was transferred to a 50 mL Teflon-lined reactor. The sealed reactor was heated to 200 °C (12 h), and then removed and cooled.

[0087] The sample inside the reactor was freeze-dried in a vacuum for 5 hours to obtain manganese ferrite nanomaterials (MnFe2O4 nanomaterial powder).

[0088] The obtained manganese ferrite nanomaterials were subjected to performance testing, and the test results are as follows: Figure 1 :

[0089] from Figure 1 As can be seen from A, the manganese ferrite nanomaterials are spherical with a particle size of 20-60 nm; the hydraulic diameter test shows that the hydraulic diameter is 982 nm and the Zeta potential is -27 mV.

[0090] from Figure 1 Image B shows that the characteristic peaks of manganese ferrite nanomaterials are consistent with those marked on the standard MnFe2O4 card (JCPDS card no. 10-0319). From Figure 1 C and D show the oxidation states of Fe and Mn. The results indicate that Fe 2p 3 / 2 The peak is divided into two peaks: a main peak at 710.6 eV and a satellite peak at 723.5 eV. Fe3+ and Fe 2+ Fe2p forms at 713.22 eV and 710.6 eV, respectively. 3 / 2 Peak. Fe 2p 1 / 2 At 723.49 eV (Fe 2+ ) and 726.16eV (Fe 3+ There is also a peak value in Mn 2p. 3 / 2 A similar splitting pattern is also observed at the peaks: a main peak at 641.17 eV and a satellite peak at 645.05 eV. The satellite structure and sharpness of Fe and Mn indicate that Fe and Mn ions in the MnFe2O4 nanomaterials are mostly in the 2+ valence state. 2+ The content (87.3%) is greater than that of Mn. 3+ Content (12.7%); similarly, Fe 2+ (67.4%) higher than Fe 3+ (32.6%). Therefore, MnFe2O4 nanomaterials may be unstable and capable of slowly releasing Mn and Fe ions.

[0091] Example 2

[0092] The application of manganese ferrite nanomaterials in enhancing the drought resistance of rice includes the following steps:

[0093] Manganese ferrite nanomaterials (MnFe2O4 nanomaterials) were mixed evenly with soil, and 1.5 kg of the mixed soil was filled into a flowerpot so that the concentration of manganese ferrite nanomaterials in the soil was 10 mg / kg.

[0094] Three rice seeds of similar shape were planted in flowerpots; these flowerpots were then placed in a greenhouse with a fixed program (photocycle of 16 / 8h (day / night), effective radiation of 15000LX, day / night temperature of 30 / 25℃, relative humidity of 60%±5%) for normal cultivation.

[0095] After the rice enters the tillering stage (after the sixth leaf), drought (FMC = 30%) is applied. During drought application, one seedling is removed from each pot, leaving two, based on the seedling growth. The drought is applied by natural drying, specifically by using a probe soil moisture sensor (TZS-IW, China) to measure the soil moisture content in each pot and adjusting the soil moisture content to 30% to achieve a drought environment. The plants are cultivated for 14 days. Before collecting plant samples, the photosynthetic intensity is measured. After collecting the samples, the dry and fresh weight of different parts of the plant, element content, leaf photosynthetic pigment content, relative expression levels of root signaling factor-related genes, ABA content, proline content, malondialdehyde content, polysaccharide content, root parameters, root angle, relative expression levels of root angle-related genes, IAA, and relative expression levels of IAA transport-related genes are measured.

[0096] Afterwards, continue to culture under drought stress until rice grains are obtained; collect the rice grains to test the rice ear, grain filling rate, thousand-grain weight, grain number, ear length, glutelin content, (Ca, P, S, Fe) content, (Mg, Zn, Mn, K) content.

[0097] Example 3

[0098] Adjust the concentration of the manganese ferrite nanomaterial in the soil in Example 2 to 1 mg / kg, and keep the rest the same as in Example 2.

[0099] Example 4

[0100] Adjust the concentration of the manganese ferrite nanomaterial in the soil in Example 2 to 50 mg / kg, and keep the rest the same as in Example 2. Comparative Example 1 normal growth, no drought (non-CK)

[0101] Keep the soil moisture content at 100%, and normally cultivate the rice.

[0102] Comparative Example 2 severe drought (CK)

[0103] Do not add manganese ferrite nanomaterial to the soil, and cultivate the rice under drought conditions (field moisture capacity FMC = 30%).

[0104] Comparative Example 3 equivalent ions (Ion)

[0105] Prepare a mixed solution with a concentration of 0.043 mmol / L of iron ions and manganese ions using MnSO4·H2O + FeSO4·7H2O, wherein the concentration of iron ions and manganese ions is equivalent to the concentration of 10 mg / kg of manganese ferrite nanomaterial, and cultivate the rice under drought conditions (field moisture capacity FMC = 30%), and cultivate the rice as in Example 2.

[0106] Test the performance of Examples 2-4 and Comparative Examples 1-3, and the test results are as follows:

[0107] Figure 2 Effects of different concentrations of MnFe2O4 nanomaterials on the growth of rice under drought stress; wherein (A) growth phenotype; (B) biomass; (C) intercellular CO2 concentration; (D) net photosynthetic rate; (E) total photosynthetic pigment in leaves; (F) carotenoid content in leaves; (G) polysaccharide content in aboveground parts; (H) root polysaccharide content. Figure 2 It can be seen that in the blank control (non-CK) without drought stress, the rice plants grow well; the control (CK) under severe drought (field moisture capacity FMC = 30%) shows significant growth retardation and leaf rolling compared to the non-CK group Figure 2 A). Figure 2The results from study B indicate that drought significantly reduced the growth of rice stems and roots, and soil application of MnFe2O4 nanomaterials alleviated this growth inhibition. (1 mg kg) -1 and 10mg kg -1 Under the treatment with MnFe2O4 nanomaterials, the aboveground biomass of rice increased significantly by 77.2% and 70.3% compared with the drought treatment, but was still lower than that of the non-drought treatment. Figure 2 C and D indicate that at 10 mg / kg -1 Treatment with MnFe2O4 nanomaterials increased intercellular CO2 concentration and net photosynthetic rate by 26.9% and 23.1%, respectively. Enhanced photosynthesis provides more nutrients for plant growth. Photosynthetic pigments participate in the absorption and transfer of light energy, constituting the primary photochemical reaction of photosynthesis. (10 mg / kg) -1 Treatment with MnFe2O4 nanomaterials significantly increased the content of total photosynthetic pigments and carotenoids in rice by 10.9% and 26.4%, respectively. Figure 2 (E, F). Furthermore, MnFe2O4 nanomaterials accumulated more polysaccharides in rice, with a 10 mg / kg increase compared to the control (CK) under severe drought (field water holding capacity FMC = 30%). -1 The promoting effect was greatest on rice stems and roots, increasing growth by 329.1% and 525.0%, respectively. Figure 2 The presence of G and H in the medium helps to provide more energy under drought stress and promote plant growth.

[0108] Table 2. Changes in nutrient element content of rice

[0109]

[0110] Table 2 shows that MnFe2O4 nanomaterials can also increase the content of nutrients in rice plants. As can be seen from Table 2, the contents of phosphorus (P), potassium (K), magnesium (Mg) and sulfide (S) are significantly increased by 14.1%, 26.5%, 46.0% and 19.8%, respectively, and the contents of phosphorus (P) and sulfur (S) in the roots are significantly increased by 27.2% and 49.8%, respectively.

[0111] Figure 3 To enhance the signal response of rice under drought stress using MnFe2O4 nanomaterials of different concentrations; among them, (A) relative expression level of CLE25 gene; (B) relative expression level of NCED3 gene; (C) ABA content in leaves; (D) proline content; (E) malondialdehyde content. Figure 3 It can be seen that under drought stress, soil application of 10 mg / kg -1 Following the application of MnFe2O4 nanomaterials, the expression level of the CLE25 gene was significantly upregulated by 54.3% compared to the drought control, demonstrating a superior promoting effect compared to other concentrations of nanomaterials. Figure 3(A). CLE, as an upstream drought-sensing gene family, activates the drought resistance of the entire plant by synthesizing the small peptide cle25 and transferring it to the stem. Compared with the control (CK) under severe drought (field holding capacity FMC = 30%), the response gene NCED3 in rice treated with MnFe2O4 nanomaterials was significantly upregulated by 59.9%. Figure 3 (B) indicates that the response signal intensity of rice to MnFe2O4 nanomaterials is enhanced under drought stress. NCED3 can encode the rate-limiting enzyme catalyzing ABA synthesis in plants. Figure 3 The results showed that, under drought stress, the application of MnFe2O4 nanomaterials significantly increased the ABA content in the aboveground parts of rice compared to the drought control, with a ABA content of 10 mg / kg significantly higher than that in the drought control. - 1 MnFe2O4 nanomaterials showed the best promoting effect (increasing ABA content by 68.6%). The increase in ABA content can further activate the stem's response to drought stress, such as stomatal closure, cuticle thickening, and proline synthesis, to reduce water loss or alleviate drought-induced oxidative damage. Furthermore, MnFe2O4 nanomaterials significantly increased the proline content in rice leaves (…). Figure 3 The content of malondialdehyde (MDA) was reduced (38.8%). Figure 3 (E, 5.4%). Proline, as a protective substance under osmotic stress, maintains homeostasis in plants under adverse conditions. Malondialdehyde (MDA), a secondary end product of lipid peroxidation, can serve as a biomarker for drought resistance.

[0112] Figure 4 Different concentrations of MnFe2O4 nanomaterials were used to promote root development in rice; (A) root angle photograph; (B) root angle; (C) IAA concentration. Figure 4 It can be seen that under drought conditions, MnFe2O4 nanomaterials induce a larger root angle in rice. Figure 4 (A and B). Root growth is closely related to IAA. The polar translocation of auxin (IAA) indirectly regulates root angle; an increase in IAA level by 74.5% ( Figure 4 (C)

[0113] Figure 5 The expression of genes controlling root angle in rice was altered by using MnFe2O4 nanomaterials of different concentrations; among them, (A) the expression intensity of the PIN gene family; (B) the expression level of the OR1 gene; (C) the expression intensity of the AUX gene family; and (D) the expression level of the DRO1 gene. Figure 5It can be seen that: compared with the control (CK) under severe drought (field moisture capacity FMC = 30%), the relative expression of the influx gene AUX family and the efflux gene PIN family gene controlling IAA polar transport is significantly up-regulated (24.7-52.1%) by the MnFe2O4 nanomaterial. In addition, DRO1 and OR1 are mainly concentrated around the root tip meristem and the static center of the root cap, and regulate the angle of the root. DRO1 regulates the elongation of different lateral root cells by mediating the difference in IAA inter-root polar transport induced by gravity, thereby regulating the root angle. However, the expression of DRO1 in the root does not change significantly. Compared with the drought control, the homologous OR1 of DRO1 is significantly up-regulated (27.4%) by the MnFe2O4 nanomaterial. Therefore, the MnFe2O4 nanomaterial can increase the root angle of rice under drought stress, help the rice plant to absorb more water to cope with drought, and 10mg kg -1 The MnFe2O4 nanomaterial has the best regulation effect at the molecular level.

[0114] Figure 6 For the 10mg kg -1 Rice yield and quality after treatment with the MnFe2O4 nanomaterial and Comparative Examples 1-3; wherein (A) rice panicle; (B) grain filling rate; (C) thousand-grain weight; (D) grain number; (E) panicle length; (F) gluten content; (G) Ca, P, S, Fe content; (H) Mg, Zn, Mn, K content. From Figure 6 It can be seen that: the MnFe2O4 nanomaterial can also drive the absorption of nutrient elements by the rice plant, resulting in changes in the content of the corresponding elements in the grain, and ultimately increasing the grain yield. Drought reduces the yield of rice, and the 10mg kg -1 The MnFe2O4 nanomaterial significantly alleviates this inhibition, and compared with the control (CK) and the equivalent ions (Ion) under severe drought (field moisture capacity FMC = 30%), the grain filling rate is increased by 61.1% and 46.7%, respectively. The thousand-grain weight, grain number and panicle length of rice are increased by 22.5%, 19.6% and 41.3% compared with the control (CK) under severe drought (field moisture capacity FMC = 30%). The Ca, P, Fe, Mn and K elements in the grain are increased by 135.1%, 21.2%, 43.6%, 31.1% and 19.3%, respectively.

[0115] Although the present application has been disclosed with reference to the preferred embodiments above, it is not intended to limit the present application, and any person skilled in the art can make various modifications and modifications without departing from the spirit and scope of the present application, therefore the protection scope of the present application should be defined by the claims.

Claims

1. Use of manganese ferrite nanomaterials in enhancing drought resistance of rice, characterized in that, The application is to mix the soil and the manganese ferrite nanometer material to form mixed soil, and then plant rice seeds for cultivation. The preparation method of the manganese ferrite nanometer material comprises the following steps: MnCl2·4H2O and FeCl3·6H2O are stirred in (CH2OH)2 until completely dissolved to obtain a mixed solution of manganese ions and iron ions; NaOH is dissolved in water to obtain a NaOH solution; The NaOH solution is added into the mixed solution at a speed of one drop per 5s, and red-brown suspended particles are gradually formed in the solution until the pH reaches 11; after sufficient stirring, the precipitate is transferred into a teflon-lined reaction kettle, heated at 200℃ for 12h, and then cooled; finally, vacuum freeze-drying is performed to obtain the manganese ferrite nanometer material.

2. Use according to claim 1, characterized in that, The concentration of the manganese ferrite nanometer material in the soil is 1-50mg / kg.

3. Use according to claim 2, characterized in that, The concentration of the manganese ferrite nanometer material in the soil is 10mg / kg.

4. Use according to claim 1, characterized in that, The Fe and Mn ions in the manganese ferrite nanomaterial are mostly in the 2+ valence state, and the Mn 2+ content is 87.3% greater than Mn 3+ content is 12.7%, Fe 2+ content is 67.4% higher than Fe 3+ content is 32.6%, which can slowly release Mn and Fe ions.

5. The use according to claim 1, characterized in that, The manganese ferrite nanometer material is spherical, with a particle size of 20-60nm, a hydrodynamic diameter of 982nm, and a Zeta potential of-27mV.

6. Use according to claim 1, characterized in that, The concentrations of manganese ions and iron ions in the mixed solution are 0.5mol / L and 1mol / L respectively.

7. The use according to claim 1, characterized in that, The concentration of the NaOH solution is 5mol / L.

8. A method for improving photosynthesis and increasing nutrient element content of rice under drought, the method comprising, The method is to mix the soil and the manganese ferrite nanometer material in claim 1 to form mixed soil, and then plant rice seeds for cultivation; wherein the concentration of the manganese ferrite nanometer material in the soil is 1-50mg / kg; the manganese ferrite nanometer material is spherical, with a particle size of 20-60nm, a hydrodynamic diameter of 982nm, and a Zeta potential of-27mV.

9. The method of claim 8, wherein, The nutrient elements include phosphorus, potassium, magnesium and sulfur.

10. A method for improving drought resistance of rice by increasing the intensity of response to drought, increasing the proline content of leaves and decreasing the malondialdehyde content, and increasing the root angle of rice, characterized by, The method is to mix the soil and the manganese ferrite nanometer material in claim 1 to form mixed soil, and then plant rice seeds for cultivation; wherein the concentration of the manganese ferrite nanometer material in the soil is 1-50mg / kg; the manganese ferrite nanometer material is spherical, with a particle size of 20-60nm, a hydrodynamic diameter of 982nm, and a Zeta potential of-27mV.

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