Method for enhancing low-temperature resistance of rape, nano initiator and preparation method of nano initiator

Abstract

The invention belongs to the field of agriculture, particularly relates to an application of a nano material in the field of agriculture, and more particularly relates to an initiation method and an initiator for enhancing low-temperature resistance of rape and a preparation method of the initiator. Seed soaking is performed by adopting the initiator composed of a ZnO-doped mesoporous cerium oxide (ZnO-CeO2) nano material and ultrapure water; the low-temperature resistance not only embodies higher seed germination rate and germination potential under low-temperature stress, but also can carry'stress memory 'to a later development stage, so that the low-temperature resistance of the rape seedlings is continuously improved.

Description

Technical Field

[0001] The invention belongs to the field of agriculture, and in particular relates to the application of nano materials in the field of agriculture, and more specifically relates to a method for enhancing the low temperature resistance of rapeseed, a nano initiator and a preparation method. Background Art

[0002] Rapeseed will suffer severe frost damage at extremely low temperatures of -7℃ to -8℃. Specifically, its growth is significantly inhibited, and the leaves turn yellow and the stems become soft. The roots of rapeseed may suffer frost damage during severe cold (below 0℃). At this time, the leaves will still appear green, but the whole plant will be frozen and dead. At the same time, rapeseed buds are in danger of frost damage below 0℃. In mild cases, the cortex will rupture, and in severe cases, the stalks will shrink, droop, and break. After being frozen, the buds of rapeseed will gradually turn yellow and dry, wither and die, seriously affecting the yield. Even if the cortex ruptures in mild cases, the effects of frostbite will continue until growth resumes, which will be manifested as longitudinal cracks in the stems, and the rapeseed will be more susceptible to disease and lodging than normal rapeseed.

[0003] As for the methods of making rapeseed resistant to low temperatures, the existing technologies mainly adopt the breeding and selection of frost-resistant varieties, inter-row cultivation and soil cultivation, application of phosphorus and potassium fertilizers, stalk removal, stalk picking and timely irrigation, etc. Summary of the invention

[0004] One of the objects of the present invention is to provide a seed priming method, so as to enhance the low temperature resistance of rapeseed and maintain the low temperature resistance in subsequent cultivation.

[0005] In order to achieve the above-mentioned object of the invention, the present invention specifically discloses a method for enhancing the low temperature resistance of rapeseed, comprising the following steps: (1) Select rapeseed seeds with full grains and perform pretreatment; (2) Soak the treated rapeseed seeds in an initiator consisting of ZnO-CeO2 NPs and ultrapure water at 20°C in the dark for 24 hours; (3) After the soaked seeds are taken out, they are primed under artificial controlled conditions; The ZnO-CeO2 nanomaterial is a mesoporous cerium oxide nanomaterial doped with 10% Zn element.

[0006] Preferably, the concentration of ZnO-CeO2 NPs is 5 mg / L.

[0007] Furthermore, the ZnO-CeO2 nanomaterial has a core-shell structure, with the ZnO layer wrapped around the outside of CeO2. The average size of the nanomaterial is 69.48±21 nm, and the average hydrodynamic diameter of the nanomaterial in ultrapure water is 228.8±3.8 nm, and the average zeta potential is -29.3±0.9 mV, indicating that the ZnO-CeO2 nanomaterial has negative electrical properties.

[0008] Preferably, the initiation conditions are air humidity of 60% and light intensity of 150 μmol m -2 s -1 The photoperiod is 14 h day and 10 h night, and the day and night temperatures are 23°C day and 18°C ​​night.

[0009] Further preferably, ultrapure water is appropriately supplemented during the initiation process to compensate for evaporated water, thereby ensuring that the seeds are always moist.

[0010] At the same time, the invention also discloses a nano-initiator suitable for the method, wherein the initiator consists of ZnO-CeO2 nanoparticles (NPs) and ultrapure water, and the ZnO-CeO2 nanomaterial is a mesoporous cerium oxide nanomaterial containing 10% elemental Zn.

[0011] Further preferably, the preparation method of the ZnO-CeO2 nanomaterial in the nano-initiator comprises: (1) Preparation of MCM-48 template, (2) preparing ZnO-doped mesoporous cerium oxide (ZnO-CeO2) nanomaterials, specifically, adding the template MCM-48 to an ethanol solution of cerium (III) nitrate hexahydrate and zinc nitrate hexahydrate, and stirring at 60°C; The product was filtered and dried, and then calcined in air at 400 °C for 2 h to obtain ZnO-doped mesoporous cerium oxide (ZnO-CeO2) nanomaterials.

[0012] Preferably, the addition ratio of the cerium (III) nitrate hexahydrate, zinc nitrate hexahydrate and ethanol solution is 3.0 g of cerium (III) nitrate hexahydrate and 0.2 g of zinc nitrate hexahydrate are added to 50 mL of ethanol solution.

[0013] Preferably, the addition ratio of the template MCM-48, cerium (III) nitrate hexahydrate, and zinc nitrate hexahydrate is 3.0 g of template MCM-48, 3.0 g of cerium (III) nitrate hexahydrate, and 0.2 g of zinc nitrate hexahydrate.

[0014] In a preferred technical solution, the dried product is heated to 400° C. at a rate of 2° C. / min in air and calcined for 2 h.

[0015] Further preferably, the prepared ZnO-doped mesoporous cerium oxide (ZnO-CeO2) nanomaterial is placed in a 2 M NaOH aqueous solution and dissolved at 60° C. for 6 hours, and then the product is collected by centrifugation and washed with distilled water and ethanol in sequence to obtain a high-purity ZnO-doped mesoporous cerium oxide (ZnO-CeO2) nanomaterial.

[0016] At the same time, the present invention further discloses a method for preparing the MCM-48 template: dissolving hexadecyltrimethylammonium bromide (5.0 g) and Pluronic F-127 (20.5 g) in a mixed solvent containing distilled water (960 mL) and ethanol (340 g); after the surfactant is completely dissolved, adding 28% ammonium hydroxide solution (100 g) at room temperature while vigorously stirring; then adding tetraethyl orthosilicate (18 g), and continuing to stir at 1000 rpm for 1 minute; then standing at room temperature for 24 hours, ultra-high speed centrifugation to obtain a white product; washing the product with water and ethanol until the pH value of the solution becomes neutral, and then calcining at 550° C. for 5 hours to remove the pore-forming template to obtain the product MCM-48 template.

[0017] The present invention can enhance the low temperature resistance of rapeseed by using an initiator composed of ZnO-doped mesoporous cerium oxide (ZnO-CeO2) nanomaterials and ultrapure water for initiation. This low temperature resistance is not only reflected in a higher seed germination rate and germination potential under low temperature stress, but also can carry the "stress memory" of the initial 24 hours of the initiation stage to the later development stage, thereby continuously improving the low temperature resistance of rapeseed seedlings. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 TEM image of ZnO-CeO2 nanomaterials.

[0019] Figure 2 The hydrodynamic diameter and zeta potential diagram of ZnO-CeO2 nanomaterials.

[0020] Figure 3 Schematic diagram of the effect of ZnO-CeO2 nanomaterials on the germination rate of rapeseed seeds under normal temperature and low temperature conditions. The data are mean ± standard deviation (n=3).

[0021] Figure 4 Schematic diagram of the effect of different concentrations of ZnO-CeO2 nanomaterials on the germination rate of rapeseed seeds under low temperature conditions. The data are mean ± standard deviation (n=3).

[0022] Figure 5 This is a schematic diagram of the germination results of rapeseed at room temperature and low temperature after seeds were soaked in ZnO-CeO2 nanoparticles.

[0023] Figure 6 This is a schematic diagram of the growth of rapeseed after seeds are soaked in ZnO-CeO2 nanoparticles and then suffer from low temperature stress at the seedling stage. DETAILED DESCRIPTION

[0024] In order to better understand the present invention, the present invention is further described below in conjunction with specific embodiments.

[0025] The reagents and instruments not specially described or indicated in the examples are all conventional commercial products and can be purchased. The conditions not specially described or indicated can be carried out according to the conventional conditions in the art or the instructions of the sellers of the relevant products.

[0026] Example 1 Preparation of ZnO-CeO2 Nanomaterials (1) Preparation of MCM-48 template: Hexadecyltrimethylammonium bromide (5.0 g) and Pluronic F-127 (20.5 g) were dissolved in a mixed solvent containing distilled water (960 mL) and ethanol (340 g). After the surfactant was completely dissolved, 28% ammonium hydroxide solution (100 g) was added while vigorously stirring at room temperature. Then, ethyl orthosilicate (18 g) was added and stirred at 1000 rpm for 1 minute. Then, the mixture was allowed to stand at room temperature for 24 h and ultracentrifuged to obtain a white product. The product was washed with water and ethanol until the pH value of the solution became neutral, and then calcined at 550 °C for 5 h to remove the porous template.

[0027] (2) Preparation of ZnO-doped mesoporous cerium oxide (ZnO-CeO2) nanomaterials: The materials were synthesized by impregnation-calcination method, as follows: the template MCM-48 (3.0 g) was added to 50 mL of ethanol solution containing cerium (III) nitrate hexahydrate (3.0) and zinc nitrate hexahydrate (0.2 g) and stirred at 60 °C. After drying, the impregnated sample was heated to 400 °C in air at a rate of 2 °C / min and calcined for 2 h. The template was then dissolved in 2 M NaOH aqueous solution at 60 °C for 6 h, and the product was collected by centrifugation and washed with distilled water and ethanol, respectively. Example 2

[0028] The particle size and potential of the nanomaterials obtained in Example 1 were measured using a dynamic light scattering instrument (Malvern Zetasizer, Nano). Specifically, 5 μL of the suspension of ZnO-CeO2 nanomaterials (200 mg / L) was added to a carbon film-supported copper mesh (Beijing Zhongxing Bairui Technology Co., Ltd., Beijing, China) and freeze-dried. The microstructure and morphology of the nanoparticles were characterized using a transmission electron microscope (JEM-200CX, JEOL, Tokyo, Japan) equipped with a CCD digital imaging system (GATAN782, USA) with a point resolution of 0.3 nm and an acceleration voltage of 80-200 kV. The TEM results are shown in Figure 2. Figure 1 shown.

[0029] TEM images show that the average size of ZnO-CeO2NPs is 69.48±21 nm, and ZnO-CeO2NPs have a core-shell structure, with CeO2 wrapped by a layer of ZnO.

[0030] The hydrodynamic diameter and zeta potential of ZnO-CeO2 nanoparticles in ultrapure water were measured by dynamic light scattering. Figure 2 As shown, the average hydrodynamic diameter of ZnO-CeO2 nanoparticles in ultrapure water is 228.8±3.8 nm, and the average zeta potential is -29.3±0.9 mV, indicating that ZnO-CeO2 nanomaterials have negative electrical properties. Example 3

[0031] Select rapeseed seeds with full grains, first disinfect the seed surface with 1% sodium hypochlorite for 10 minutes, and then rinse with ultrapure water for 5 times to complete the seed pretreatment. Subsequently, the disinfected seeds were soaked in ZnO-CeO2 NPs and ultrapure water at 20°C in the dark for 24 h, and the ratio of seed weight to solution volume was 1:5 (g / mL). After the initiation, the rapeseed seeds were placed in a culture dish containing 3 mL of solution. Each culture dish contained 50 seeds, and each treatment contained 3 replicates. The experiment used an artificial climate chamber (Ningbo Ledian Instrument Manufacturing Co., Ltd., model: RLD-1000D-4) for seed germination and seedling growth. The culture parameters were: 14 h day / 10 h night, light intensity 12 000 Lux, relative humidity 60%, normal temperature setting 22°C, low temperature setting 8°C, and 1-2 mL of ultrapure water was added to each culture dish during the culture period to compensate for the evaporated water.

[0032] The germination rate was evaluated by recording the number of seeds germinated every 24 h, with the radicle length not less than the seed diameter as the germination standard, and the record was made for 7 days. On the 4th day, 1-2 mL of ultrapure water was added to each culture dish to compensate for the evaporated water. The germination potential and germination rate were counted on the 5th and 7th days respectively. After the germination, 10 seedlings were randomly selected to measure the fresh weight of the seedlings. The dry weight of the seedlings was measured after drying at 60℃ for 48 h, and the germination index and vitality index were calculated: Germination rate = N 1 / N ×100%, Germination potential = N 2 / N ×100% in, N Represents the number of seeds tested, N 1 is the normal number of germinated grains at the end of the seventh day, N 2 represents the normal number of germinated grains on the 3rd day.

[0033] The experimental results are shown in Figure 3 .

[0034] It can be seen that the germination rate of rapeseed seeds treated with ZnO-CeO2 nanoparticles at room temperature is higher than that of the water control group, indicating that ZnO-CeO2 seed priming can significantly promote the germination rate of rapeseed seeds at room temperature. Under low temperature stress conditions, compared with the water control, ZnO-CeO2NPs seed soaking increased the germination rate of rapeseed seeds at low temperatures. Example 4

[0035] According to the method in Example 3, the concentration of ZnO-CeO2 nanomaterials was 5, 10, 20, and 40 mg / L, and the water treatment was used as the control. The germination experiment was carried out at low temperature to compare the effects of different concentrations of ZnO-CeO2 nanomaterials on seed germination. The experimental results are shown in Figure 4 and Figure 5 .

[0036] The results showed that 5 mg / L ZnO-CeO2 had the best effect on promoting rapeseed germination at low temperature. After soaking seeds with ZnO-CeO2 nanoparticles, the germination potential of rapeseed in the normal temperature group increased from 69.3 to 87.3, and the germination potential of rapeseed in the low temperature group increased from 56.7 to 60.5. Example 5

[0037] According to the method in Example 3, ZnO-CeO2 NPs were used to prime Ningza 158 rapeseed seeds, and water treatment was used as a control. After the priming, the seeds were sown in the soil, 2 seeds were sown in each pot, and each treatment was repeated three times. The seeds were placed in a light incubator for cultivation, with an air humidity of 60% and a light intensity of 150 μmol m -2s -1 , the photoperiod was 14h / 10h, and the day and night temperature was 23°C / 18°C. When the rapeseed reached the four-leaf stage, four seedlings were placed under low temperature (2°C / 0°C) for 48 h. After the stress was over, the frost damage index was calculated, and the aboveground parts were collected to measure the dry weight to explore whether the "stress memory" can be carried to the later development stage and enhance the low temperature resistance of rapeseed seedlings. The results of the effect of nanoparticle seed soaking on the low temperature resistance of four-leaf rapeseed seedlings are shown in Table 1; Table 1.

[0038] Compared with the water control (0.1313 g), the ZnO-CeO2NPs soaked seeds significantly ( p < 0.05) increased the aboveground biomass of Ningza 158 (0.2851 g) (Table 1). After the stress ended, the ZnO-CeO2NPs seed soaking treatment reduced the freezing injury index of Ningza 158 seedlings (0.67), indicating that the "stress memory" induced by ZnO-CeO2NPs at the very beginning (24 hours) of the plant life cycle can be carried to the later development stage, enhancing the low temperature resistance of rapeseed seedlings.

[0039] The above is a specific implementation of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications are also considered to be within the protection scope of the present invention.

Claims

1. A method for enhancing the low temperature resistance of rapeseed, characterized in that: The following steps are involved: (1) Select rapeseed seeds with full grains and perform pretreatment; (2) Soak the treated rapeseed seeds in an initiator consisting of ZnO-CeO2 NPs and ultrapure water at 20°C in the dark for 24 hours; (3) After the soaked seeds are taken out, they are primed under artificial controlled conditions; The ZnO-CeO2 nanomaterial is a mesoporous cerium oxide nanomaterial doped with 10% Zn element.

2. The method for enhancing the low temperature resistance of rapeseed according to claim 1, characterized in that ZnO -CeO2 NPs concentration was 5 mg / L; the ratio of seed weight to solution volume was 1:5 (g / mL).

3. The method for enhancing the low temperature resistance of rapeseed according to claim 1, characterized in that: The ZnO-CeO2 nanomaterial is a core-shell structure, with a ZnO layer wrapped around the outside of CeO2. The average size of the nanomaterial is 69.48±21 nm, and the average hydrodynamic diameter of the nanomaterial in ultrapure water is 228.8±3.8 nm, and the average zeta potential is -29.3±0.9 mV.

4. The method for enhancing the low temperature resistance of rapeseed according to claim 1, characterized in that: The initiation conditions were air humidity of 60% and light intensity of 150 μmol m -2 s -1 The photoperiod is 14h day and 10h night, and the day and night temperatures are 23°C day and 18°C ​​night.

5. A nano-initiator suitable for use in a method for enhancing the low temperature resistance of rapeseed according to any one of claims 1 to 4, characterized in that: The nano-initiator consists of ZnO-CeO2 nanoparticles (NPs) and ultrapure water, and the ZnO-CeO2 nanomaterial is a mesoporous cerium oxide nanomaterial doped with 10% Zn element.

6. A method for preparing the ZnO-CeO2 nanomaterial in the nano-initiator described in claim 5, characterized in that it comprises: (1) Preparation of MCM-48 template, (2) Preparation of ZnO-doped mesoporous cerium oxide (ZnO-CeO2) nanomaterials: adding the template MCM-48 into an ethanol solution of cerium (III) nitrate hexahydrate and zinc nitrate hexahydrate and stirring at 60 °C; The product was filtered and dried, and then calcined in air at 400 °C for 2 h to obtain ZnO-doped mesoporous cerium oxide (ZnO-CeO2) nanomaterials.

7. The method according to claim 6, characterized in that: The addition ratio of the cerium (III) nitrate hexahydrate, zinc nitrate hexahydrate and ethanol solution is 3.0 g of cerium (III) nitrate hexahydrate and 0.2 g of zinc nitrate hexahydrate are added to 50 mL of ethanol solution.

8. The method according to claim 6, characterized in that: The addition ratio of the template MCM-48, cerium (III) nitrate hexahydrate, and zinc nitrate hexahydrate is 3.0 g of template MCM-48, 3.0 g of cerium (III) nitrate hexahydrate, and 0.2 g of zinc nitrate hexahydrate.

9. The method according to claim 6, characterized in that: The dried product was calcined in air at a temperature of 2 °C / min to 400 °C for 2 h.

10. The method according to claim 6, characterized in that: The prepared ZnO-doped mesoporous cerium oxide (ZnO-CeO2) nanomaterial was placed in a 2 M NaOH aqueous solution and dissolved at 60°C for 6 hours. The product was then collected by centrifugation and washed with distilled water and ethanol in turn to obtain a high-purity ZnO-doped mesoporous cerium oxide (ZnO-CeO2) nanomaterial.

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