Application of Fe3O4@SiO2 Nanocomposites in Promoting Seed Germination and Seedling Growth of Wheat under Drought Stress

Abstract

The application belongs to the technical field of biology and specifically relates to application of Fe3O4@SiO2 nanocomposites in promoting seed germination and seedling growth of wheat under drought stress, wherein the promoting effect of the Fe3O4@SiO2 nanocomposites is significantly better than that of single materials, indicating that there is a synergistic effect between the two nanocomponents, so as to play a stronger physiological promoting effect in the seed germination and seedling growth stage. 2 The Fe3O4@SiO2 NCs can effectively improve the growth performance of wheat under drought stress, including improvement of total root length, average length of main root, number of lateral roots, maximum root width, maximum root depth, width-depth ratio, convex hull area, fresh weight of root system and root weight under drought treatment, and can be used for preparing seed coating agents and plant growth promoters, and has a wide application prospect.

Description

Technical Field

[0001] This invention belongs to the field of biotechnology, specifically relating to the application of Fe3O4@SiO2 nanocomposite materials in promoting wheat seed germination and seedling growth under drought stress. Background Technology

[0002] Wheat (Triticum aestivum L.), as a staple food source, is a cornerstone crop for ensuring global food security. However, drought stress has become a core abiotic limiting factor restricting stable and high wheat yields, especially in dryland agricultural ecosystems with extremely scarce water resources, such as the Hexi Corridor oases. Water shortages lead to significant annual wheat yield losses, seriously threatening the stability of regional and even national food supply. Therefore, elucidating the response mechanism of wheat to drought and developing new drought-resistant and high-yield germplasm are urgent tasks in the field of crop genetics and breeding.

[0003] The root system is the main organ for plants to absorb water and nutrients, and its structure and functional characteristics directly determine the plant's ability to perceive and tolerate soil drought. Under drought stress, the root system optimizes water absorption efficiency by changing its conformation, anatomical structure, and metabolic pathways. Among these, the root cortex serves as a key channel for the radial transport of water and solutes from the epidermis to the stele, and also undertakes multiple physiological functions such as nutrient storage, aerenchyma formation, and stress signal transduction. The cell vitality, thickness, and senescence process of the cortex directly affect the resistance and efficiency of lateral water transport, thereby regulating the overall water balance of the plant.

[0004] Existing research indicates that drought stress often accelerates programmed senescence (RCS) of the root cortex. Moderate root cortex senescence can reduce carbon consumption during root respiration, redistributing resources to new root growth or aboveground parts—an adaptive conservation strategy. However, premature or excessive cortex senescence disrupts the integrity of the cortex structure, increases apoplastic barrier resistance to radial water transport, significantly reduces water uptake efficiency, and induces secondary damage such as reactive oxygen species bursts and ion imbalances, ultimately accelerating premature senescence and yield loss throughout the plant. Currently, the molecular regulatory network of drought-induced root senescence remains unclear, particularly regarding how to precisely regulate the initiation points and progression rate of cortex senescence to avoid its negative effects. Effective genetic manipulation targets and agronomical regulatory strategies are still lacking.

[0005] In recent years, nanotechnology in agriculture has provided a new pathway for regulating crop drought resistance. Metal nanoparticles, due to their unique physicochemical properties, have shown significant potential in mitigating the damage caused by drought stress to crops. For example, Wang Yuxia et al. studied the effects of silica nanoparticles on the growth and physiology of wolfberry seedlings under drought stress. The results showed that an appropriate concentration (100 mg / L) of silica nanoparticles could effectively enhance the physiological tolerance of wolfberry seedlings to drought stress through multiple synergistic pathways. [1] Tian Qinyu et al. studied the effects of nano-ferric oxide on sugar beet seed germination under drought stress. Their results showed that the effect of nano-ferric oxide may involve interactions of concentration, time, and environmental conditions, and its mode of action can be regulated by the environment: enhancing antioxidant defense under adversity and promoting growth and development under suitable conditions. [2] However, the synergistic effect of different metal nanoparticles and their joint regulatory mechanism on the aging process of root cortex have not yet been revealed. There is still a lack of systematic technical solutions on how the two can synergistically maintain the integrity of cortical structure, optimize radial water transport and delay functional aging under drought stress.

[0006] Therefore, in response to the above-mentioned technical problems, this invention studies a composite metal nanoparticle Fe3O4@SiO2 NCs, which can precisely regulate the senescence process of wheat root cortex and improve water use efficiency and yield under drought conditions. This is of great significance for achieving stable wheat cultivation and stress-resistant breeding under drought stress.

[0007] References:

[0008] [1] Wang Yuxia. Effects of silica nanoparticles on growth and physiology of Lycium barbarum seedlings under drought stress [J]. Gansu Forestry, 2026, (01): 30-35.

[0009] [2] Tian Qinyu, Hu Huabing, Wang Ronghua, et al. Effects of nano-ferric oxide on sugar beet seed germination under drought stress [J]. Seeds, 2025, 44(12):115-120. DOI:10.16590 / j.cnki.1001-4705.2025.12.115. Summary of the Invention

[0010] The primary objective of this invention is to provide the application of Fe3O4@SiO2 nanocomposites in promoting wheat seed germination under drought stress.

[0011] The second objective of this invention is to provide the application of Fe3O4@SiO2 nanocomposites in promoting wheat seedling growth under drought stress.

[0012] A third objective of this invention is to provide the application of Fe3O4@SiO2 nanocomposites in delaying wheat root senescence under drought stress.

[0013] The fourth objective of this invention is to provide the application of Fe3O4@SiO2 nanocomposites in increasing wheat yield under drought stress.

[0014] Preferably, the Fe3O4@SiO2 nanocomposite material is prepared by the following method: (1) Fe3O4 NPs and Tween-60 are dispersed in cyclohexane by ultrasonic treatment;

[0015] (2) After vortex mixing of the reaction solution obtained in step (1), add ammonium hydroxide to make a transparent brown solution;

[0016] (3) After adding tetraethyl orthosilicate to the solution in step (2), react at room temperature, and precipitate Fe3O4@SiO2NCs with methanol, and collect by centrifugation.

[0017] The fifth objective of this invention is to provide a seed soaking agent that promotes wheat seed germination, wherein the seed soaking agent contains Fe3O4@SiO2 nanocomposite material.

[0018] The sixth objective of this invention is to provide a wheat growth promoter containing Fe3O4@SiO2 nanocomposite material.

[0019] The seventh objective of this invention is to provide a method for promoting wheat seed germination under drought stress, comprising the following steps:

[0020] Select plump wheat seeds of uniform size, disinfect them with 5% sodium hypochlorite solution for 10 min, and then rinse them with deionized water to remove residual disinfectant. Place the disinfected seeds in Fe3O4@SiO2 nanocomposite material and soak them in the dark at 25 ℃ for 24 h. The ratio of seed mass to volume of Fe3O4@SiO2 nanocomposite material is 1:5. After soaking, remove the seeds and dry the surface moisture for germination.

[0021] The beneficial effects of this invention are as follows: This invention provides the application of Fe3O4@SiO2 nanocomposites in promoting wheat seed germination and seedling growth under drought stress. The promoting effect of the Fe3O4@SiO2 nanocomposites is significantly better than that of the single material, indicating a synergistic effect between the two nanocomponents, thereby exerting a stronger physiological promoting effect during the seed germination and seedling growth stages. Simultaneously, Fe3O4@SiO2NCs can effectively improve the growth performance of wheat under drought stress, including increases in total root length, average taproot length, number of lateral roots, maximum root width, maximum root depth, width-to-depth ratio, convexity area, root fresh weight, and root weight under drought treatment. It can be used to prepare seed coating agents and plant growth promoters, and has broad application prospects. Attached Figure Description

[0022] Figure 1. Morphology, composition and structural characterization of Fe3O4@SiO2NCs.

[0023] Note: A: Scanning electron microscope (SEM) image of Fe3O4@SiO2 nanocomposites (NCs) [scale 200 nm]. The red arrows visually depict the positions of Fe3O4NCs, illustrating the formation of Fe3O4@SiO2NCs through their bonding. B: EDS spectroscopy showing elemental analysis of Fe3O4@SiO2 NCs. C: FTIR spectra of Fe-NPs and Fe3O4@SiO2NCs. D: XRD patterns of Fe-NPs and Fe3O4@SiO2NCs. The blue line represents Fe3O4 NPs, and the red line represents Fe3O4@SiO2 NCs.

[0024] Figure 2 Effects of SiO2@Fe3O4 NCs on seedling growth and germination characteristics of different drought-resistant wheat varieties.

[0025] Note: (A) Plant height on day 8, (B) Plant height on day 15, (C) Leaf area on day 8, (D) Leaf area on day 15, (E) Relative water content, (F) Dry weight, (G) Germination potential, and (H) Germination rate.

[0026] The white and black bars represent Ningchun 16 and Dingxi 48, respectively. The gray shaded area represents different concentration treatments of SiO2@Fe3O4 nanomaterials, with CK serving as the control. Different lowercase letters on the bars indicate significant differences between different treatments of the same variety (P < 0.05); the ns, *, and ** symbols above indicate no significant difference (P > 0.05), significant difference (P < 0.05), and highly significant difference (P < 0.01) between two varieties under the same treatment, respectively. Data are expressed as mean ± SD, n = 3.

[0027] Figure 3 The effects of SiO2@Fe2O3 nanomaterials on the growth and germination characteristics of seedlings of different drought-resistant wheat varieties.

[0028] Note: (A) Plant height on day 8, (B) Plant height on day 15, (C) Leaf area on day 8, (D) Leaf area on day 15, (E) Relative water content, (F) Dry weight, (G) Germination potential, (H) Germination rate.

[0029] Figure 4 The effects of SiO2@ZnO nanomaterials on the growth and germination characteristics of seedlings of different drought-resistant wheat varieties.

[0030] Note: (A) Plant height on day 8, (B) Plant height on day 15, (C) Leaf area on day 8, (D) Leaf area on day 15, (E) Relative water content, (F) Dry weight, (G) Germination potential, (H) Germination rate.

[0031] Figure 5 The effects of SiO2@MgO nanomaterials on the growth and germination characteristics of seedlings of different drought-resistant wheat varieties.

[0032] (A) Plant height on day 8, (B) Plant height on day 15, (C) Leaf area on day 8, (D) Leaf area on day 15, (E) Relative water content, (F) Dry weight, (G) Germination potential, (H) Germination rate.

[0033] Figure 6 The effects of SiO2@Al2O3 nanomaterials on the growth and germination characteristics of seedlings of different drought-resistant wheat varieties.

[0034] Note: (A) Plant height on day 8, (B) Plant height on day 15, (C) Leaf area on day 8, (D) Leaf area on day 15, (E) Relative water content, (F) Dry weight, (G) Germination potential, (H) Germination rate.

[0035] Figure 7 The effects of SiO2@Al2O3 nanomaterials on the growth and germination characteristics of seedlings of different drought-resistant wheat varieties.

[0036] Note: (A) Plant height on day 8, (B) Plant height on day 15, (C) Leaf area on day 8, (D) Leaf area on day 15, (E) Relative water content, (F) Dry weight, (G) Germination potential, (H) Germination rate.

[0037] Figure 8 The effect of composite nanomaterials on the photosynthetic pigment content of different drought-resistant wheat varieties.

[0038] Note: (A) Chlorophyll a content, (B) Chlorophyll b content, (C) Total chlorophyll content, (D) Carotenoid content

[0039] Figure 9 The effects of composite nanomaterials on the antioxidant system of different drought-resistant wheat varieties.

[0040] Note: (A) Ascorbate peroxidase activity, (B) Superoxide dismutase activity, (C) Peroxidase activity, (D) Malondialdehyde content

[0041] Figure 10 The effects of single nanomaterials and composite nanomaterials on seed germination and seedling growth.

[0042] Note: Data analysis of (A) germination potential, (B) germination rate, and (C) dry weight. Different lowercase letters on the column indicate significant differences between treatments (P < 0.05).

[0043] Figure 11. The mitigating effect of exogenous Fe3O4@SiO2NCs on aboveground traits of wheat under drought stress.

[0044] Note: (A) Comparative images of plants at different concentrations, (B) Leaf area, (C) Plant height, (D) SPAD, (E) Fresh weight of aboveground parts, (F) Dry weight of aboveground parts, and (G) Statistical analysis of relative water content.

[0045] Figure 12 The mitigating effect of exogenous Fe3O4@SiO2NCs on wheat root traits under drought stress.

[0046] Note: (A) Comparative images of wheat roots at different concentrations, (B) Total root length, (C) Average taproot length, (D) Number of lateral roots, (E) Maximum root width, (F) Maximum root depth, (G) Width-to-depth ratio, (H) Convex bulge area, (I) Fresh root weight, and (J) Statistical analysis of root dry weight.

[0047] Figure 13 Effects of exogenous Fe3O4@SiO2 NCs on ABA and RCS of the roots of “Ruichun 1” and “Dingxi 48”.

[0048] Note: Statistical analysis of (A) Ruichun 1-abscisic acid content, (B) Dingxi 48-abscisic acid content, (C) Ruichun 1-cortical cavity tissue area, (D) Dingxi 48-cortical cavity tissue area, (E) Ruichun 1-cortical aging percentage and (F) Dingxi 48-cortical aging percentage.

[0049] Figure 14 Effects of Fe3O4@SiO2NCs on grain yield of two wheat varieties under normal conditions (CK) and drought conditions (DS).

[0050] Note: CK, 300 mm conventional irrigation; DS, 240 mm reduced irrigation (20%); CK + NCs, 300 mm conventional irrigation + root application of 75 mg / L nano-solution; DS + NCs, 240 mm reduced irrigation (20%) + root application of 75 mg / L nano-solution. Bar graphs represent mean ± standard deviation. Different letters above the bars indicate significant differences (P < 0.05) among all treatments. Detailed Implementation

[0051] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.

[0052] It should be noted that, unless otherwise specified, all raw materials used in the following embodiments are commercially available products, and all methods used are available from the literature.

[0053] It should be noted that the following experiments of this invention were conducted indoors in pots at the artificial climate chamber of Gansu Agricultural University in Lanzhou, Gansu Province (38°85′N, 115°30′E). First, plump, uniform, clean, and disease-free seeds were selected. These seeds were sterilized with 75% ethanol for 15 min, rinsed with distilled water, and then soaked in distilled water for 12 h in a dark incubator at 25°C. Seeds with uniform white sprouts were sown into culture pots (12 cm in diameter, 13 cm in height) containing 2 kg of culture medium. The culture medium consisted of a mixture of field topsoil (0–20 cm), peat moss (0–6 mm, pH 6.0), and sand in a 3:1:1 (v:v:v) ratio. The soil was sandy loam containing 18.43 g·kg⁻¹ of organic matter. -1 Alkaline nitrogen 112 mg·kg -1 Available phosphorus 33.67 mg·kg -1 Available potassium 207 mg·kg -1 .

[0054] The experimental materials selected were the drought-resistant variety "Ruichun No. 1" and the drought-sensitive variety "Dingxi No. 48" from the previous screening. 2-3 seeds were sown separately in each pot, and after the cotyledons emerged and spread out, one seedling was transplanted. Treatment began when the wheat reached the two-leaf stage and continued until harvest. The cultivation conditions were 28±2℃ light and 22±2℃ darkness for 12 hours each, relative humidity of 40%-50%, and daytime light intensity of 600 μmol / m². -2 ·s -1 During the experiment, the culture pots were weighed and the soil moisture sensor was installed daily to ensure that the moisture content remained within the set range.

[0055] Example 1: Preparation and Characterization of Fe3O4@SiO2 NCs

[0056] 1. Preparation of Fe3O4@SiO2 NCs

[0057] Both SiO2 and Fe3O4 NPs were purchased from Shanghai Huijing Asia Nanomaterials Co., Ltd. The SiO2 NPs had a purity of 99.9%, an average particle size of 5-20 nm, and a specific surface area of ​​193 m². 2 / g. Fe3O4 NPs have a purity of 99.5%, an average particle size of 30 nm, and a specific surface area of ​​50-100 m². 2 / g.

[0058] 0.24 mg of Fe3O4 NPs and 0.5 g of Tween-60 were dispersed in 4.2 ml of cyclohexane by sonication. The reaction mixture was then vortexed and 35 μl of ammonium hydroxide was added to prepare a transparent brown solution. 12 μl of TEOS was then added, and the reaction was carried out at room temperature for 16 hours. Fe3O4@SiO2NCs were precipitated with methanol, and the final product was collected by centrifugation.

[0059] 2. Characterization of Fe3O4@SiO2 NCs

[0060] The morphology and microstructure of Fe3O4@SiO2 NCs were characterized using scanning electron microscopy (ZEISS GeminiSEM 300, Germany). For surface elemental analysis, energy-dispersive X-ray spectroscopy (EDS) was performed using a FEI QUANTA FEG 650 (EDAX Inc. Genesis XM). The mineral crystals of the NCs were identified by X-ray diffraction (XRD) using a computer-controlled diffractometer (Bruker D8 Advance). The presence of functional groups on the surface of the carbon nanotubes was determined using Fourier transform infrared spectroscopy (FTIR). The FTIR spectra were then compared with spectra from various spectral databases to identify specific functional groups present on the NCs.

[0061] 3. Results and Analysis

[0062] The morphology, composition, and crystal structure of the prepared Fe3O4@SiO2 NCs were systematically characterized and analyzed using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). SEM images showed that the Fe3O4@SiO2 NCs exhibited irregular spherical or aggregated morphologies with a particle size distribution of approximately 50–150 nm. The red arrows in the figures clearly indicate the positions of the Fe3O4 NCs within the SiO2 matrix, confirming the successful preparation of a core-shell structured nanocomposite material formed by the combination of magnetic nanoparticles and a silica coating layer. Figure 1A). EDS spectroscopy revealed the elemental composition of the synthesized NCs, detecting distinct characteristic peaks for Fe, Si, and O, further verifying the coexistence of Fe3O4 and SiO2 components in the nanocomposite material. Figure 1 B). FTIR spectroscopy confirmed that the magnetic nanoparticles were successfully coated with a silica shell, and Fe3O4@SiO2 NCs (red line) were detected at 1090 cm⁻¹. -1 and 800 cm -1 Characteristic absorption bands appear at 580 cm⁻¹, corresponding to the asymmetric and symmetric stretching vibrations of the Si–O–Si bond, respectively. -1 The absorption peak at 3400 cm⁻¹ is attributed to the Fe–O stretching vibration of the magnetite core. In contrast, bare Fe-NPs (blue line) show an absorption peak at 3400 cm⁻¹. -1 A broad O–H stretching vibration absorption band is observed at 580 cm⁻¹. -1 The Fe–O characteristic peak is shown at ( ) Figure 1 C). XRD analysis was used to evaluate the crystal structure and purity of the prepared nanomaterials. The XRD pattern of Fe3O4NCs (blue line) showed obvious diffraction peaks at 30.1°, 35.5°, 43.1°, 53.4°, 57.0°, and 62.6°, corresponding to the (220), (311), (400), (422), (511), and (440) crystal planes of the cubic spinel Fe3O4 structure (JCPDS No. 19-0629). Notably, Fe3O4@SiO2 NCs (red line) retained all the characteristic diffraction peaks of the Fe3O4 core, and no obvious peak shifts or impurity peaks were observed, indicating that the silica coating process did not change the crystal structure of the magnetite nanoparticles. Figure 1 D).

[0063] Example 2: The promoting effects of different nanomaterials and different concentrations on seed germination and seedling growth

[0064] 1. Method

[0065] Seeds of the cultivars "Ningchun 16" and "Dingxi 18" with plump and uniformly sized kernels were selected as experimental materials. The seeds were first surface-sterilized with a 5% sodium hypochlorite solution for 10 min, then rinsed five times with deionized water to remove residual disinfectant. Subsequently, suspensions of SiO2@Fe3O4, SiO2@Fe2O3, SiO2@ZnO, SiO2@MgO, and SiO2@Al2O3 were prepared at concentrations of 10, 25, 50, 75, and 100 mg / L. The sterilized seeds were placed in these different treatment solutions and soaked for 24 h at 25 ℃ in the dark, with a seed-to-solution volume ratio of 1:5. After soaking, the seeds were removed and their surface moisture was dried for subsequent germination experiments.

[0066] To evaluate the effects of different nanotreatments on seed germination and seedling growth, treated seeds were evenly placed in sterile petri dishes with a diameter of 9 cm. Two layers of filter paper were placed at the bottom of each dish, and 25 seeds were placed in each dish. An equal volume of deionized water was added. Each treatment was repeated five times. The petri dishes were incubated in a controlled climate chamber at 25 ± 1 ℃ for 7 days. The filter paper was kept moist during the experiment, and the same treatment solution was added as needed. Seed germination was recorded periodically during the germination process. Germination was defined as the radicle breaking through the seed coat and reaching more than half the seed length. The formulas for calculating germination potential and germination rate are as follows:

[0067] Germination potential = Number of seeds that germinate normally within a specified time / Total number of seeds tested × 100%.

[0068] Germination rate = (Number of normally germinated seeds at the end of the experiment / Total number of seeds tested) × 100%.

[0069] Subsequently, the plant height was determined by measuring the length from the cotyledon node to the terminal bud using a ruler, the stem diameter was measured using calipers, and the leaf area was determined using the length-width ratio method. Each treatment was replicated five times. The relative moisture content was determined by weighing, based on the third functional leaf, between 9:00 and 11:00. Following this, five wheat seedlings from each treatment were taken, divided into above-ground and below-ground portions, placed in kraft paper envelopes, and after recording the measurements, placed in a precision drying oven. The oven was set to 105 ℃ for 20 min to fix the seedlings, then dried at 85 ℃ to constant weight, and the dry weight was obtained by weighing.

[0070] 2. Results

[0071] To screen for the best mitigation nanocomposite materials and their applicable concentrations, the effects of five SiO2-based nanomaterials (SiO2@Fe3O4, SiO2@Fe2O3, SiO2@ZnO, SiO2@MgO, and SiO2@Al2O3) at different concentrations on the seedling growth and germination characteristics of two wheat varieties (Ningchun 16 and Dingxi 48) under drought stress were systematically compared. Figure 2 – Figure 5 Compared with DS, the SiO2@Fe3O4 treatment significantly increased the plant height, leaf area, relative water content, dry weight, germination potential, and germination rate of the two wheat varieties by 15.63–47.10%, 18.63–34.76%, 65.08–291.95%, 59.95–142.16%, 1.42–50.45%, and 5.18–45.82%, respectively (P < 0.05). Figure 2Compared with DS, SiO2@Fe2O3 treatment significantly increased the plant height, leaf area, relative water content, dry weight, germination potential, and germination rate of both varieties by 46.80–65.20%, 25.90–45.46%, 86.36–170.00%, 50.18–116.04%, 6.96–19.38%, and 8.76–49.40%, respectively (P < 0.05). Figure 3 Compared with DS, SiO2@ZnO treatment significantly increased plant height, leaf area, relative water content, dry weight, germination potential, and germination rate of both varieties by 2.49–48.02%, 4.77–32.19%, 6.95–196.69%, 14.09–86.92%, 7.90–23.43%, and 5.78–31.87%, respectively (P < 0.05). Figure 4 Compared with DS, SiO2@MgO treatment significantly increased plant height, leaf area, relative water content, dry weight, germination potential, and germination rate of both varieties by 10.85–74.80%, 22.01–43.08%, 97.54–266.44%, 56.89–100.75%, 1.26–18.48%, and 28.88–55.58%, respectively (P < 0.05). Figure 5 Compared with DS, SiO2@Al2O3 treatment significantly increased the plant height, leaf area, relative water content, dry weight, germination potential, and germination rate of both varieties by 35.79–63.65%, 8.23–41.20%, 192.03–346.95%, 41.95–94.29%, 5.03–22.59%, and 18.53–47.21%, respectively (P < 0.05). Figure 6 Concentration-effect analysis showed that the treatments of 75 mg / L SiO2@Fe3O4, 25 mg / L SiO2@Fe2O3, 25 mg / L SiO2@ZnO, 25 mg / L SiO2@MgO, and 100 mg / L SiO2@Al2O3 had the most significant promoting effects overall. Under these treatments, the seedling growth, physiological state, and germination characteristics of both varieties reached a high level.

[0072] To further verify the advantages of composite nanomaterials, a comparative analysis was conducted on the effects of SiO2 treatment alone and composite nanomaterial treatment on wheat growth and germination. The results showed that drought stress significantly inhibited seedling growth and germination in both varieties: compared with the control (CK), plant height, leaf area, relative water content, dry weight, germination potential, and germination rate decreased by 21.1–33.9% under the DS treatment. Figure 7While applying SiO2 alone could partially alleviate the aforementioned inhibitory effects, the recovery of each indicator was limited and most did not reach a significant level (P > 0.05). In contrast, all five composite nanomaterial treatments significantly improved the above indicators, with increases ranging from 32.2–74.8% (plant height), 45.5–86.9% (leaf area), 19.4–50.5% (relative water content), 31.9–55.6% (dry weight), 51.3–144.8% (germination potential), and 68.6–91.9% (germination rate) (P < 0.05). Figure 7 (AH). This indicates that the introduction of Fe3O4, MgO, and Al2O3 are key determinants of the enhanced drought mitigation effect of SiO2 nanomaterials. Consistent with the screening results above, Ningchun 16 showed better overall recovery under composite treatment than Dingxi 48, with significant increases in plant height, leaf area, relative water content, dry weight, germination potential, and germination rate of 14.3%, 39.4%, 17.0%, 18.1%, 21.9%, and 19.4%, respectively (P < 0.05). Notably, SiO2@Fe3O4, SiO2@MgO, and SiO2@Al2O3 exhibited the strongest or most stable promoting effects across multiple indicators, suggesting that these three materials have higher application potential.

[0073] To preliminarily elucidate the physiological mechanism by which composite nanomaterials alleviate drought stress, the photosynthetic pigment content and key enzyme activities of the antioxidant system were measured in two wheat varieties under their respective optimal concentration treatments (SiO2@Fe3O4: 75 mg / L, SiO2@Fe2O3: 25 mg / L, SiO2@ZnO: 25 mg / L, SiO2@MgO: 25 mg / L, SiO2@Al2O3: 100 mg / L). Drought stress significantly disrupted photosynthetic pigment metabolism and antioxidant balance. Compared with the control (CK), the DS treatment resulted in a significant decrease of 23.5%, 25.2%, 20.1%, and 25.9% in chlorophyll a, chlorophyll b, total chlorophyll, and carotenoid contents, respectively (P < 0.05). Figure 8 (AD), indicating that drought stress caused significant damage to the photosynthetic system. Treatment with composite nanomaterials significantly restored photosynthetic pigments. Compared with DS, the five composite treatments significantly increased chlorophyll b, total chlorophyll, and carotenoids by 0.2–65.4%, 43.5–65.4%, and 24.3–53.2%, respectively (P < 0.05). Figure 9 (AD). Among them, SiO2@Fe3O4 showed the most outstanding performance in terms of photosynthetic pigment content and the activity of key enzymes in the antioxidant system.

[0074] The activities of key enzymes in the antioxidant system and the content of malondialdehyde (MDA) were further determined under the optimal concentration treatments (SiO2@Fe3O4: 75 mg / L, SiO2@Fe2O3: 25 mg / L, SiO2@ZnO: 25 mg / L, SiO2@MgO: 25 mg / L, SiO2@Al2O3: 100 mg / L). Figure 9 Compared with the control (CK), the DS treatment significantly increased APX, SOD, and POD by 68.3%, 61.5%, and 127.8%, respectively, while the MDA content also significantly increased by 33.2% (P < 0.05), indicating that although drought activated the antioxidant defense system, it was insufficient to completely prevent oxidative damage. Compared with DS, the activities of APX, SOD, and POD, and the content of MDA decreased by 31.8–67.7%, 36.6–79.6%, 25.2–74.1%, and 10.7–32.9%, respectively, under the five combined treatments (P < 0.05). Among them, SiO2@Fe3O4 showed the most outstanding performance in mitigating oxidative damage. Inter-varietal comparisons showed that, compared with Dingxi 48, Ningchun 16 exhibited a significant 21.3% reduction in MDA content under combined treatment (P < 0.05), indicating that Ningchun 16 possesses a lower level of oxidative damage and a more efficient antioxidant system regulation capability, which is consistent with its stronger mitigation effect on growth and germination indicators.

[0075] Example 3: The promoting effect of Fe3O4@SiO2 NCs on seed germination and seedling growth

[0076] 1. Method

[0077] Plump and uniformly sized "Ruichun No. 1" seeds were selected as experimental materials. The seeds were first surface-sterilized with a 5% sodium hypochlorite solution for 10 min, then rinsed five times with deionized water to remove residual disinfectant. Subsequently, suspensions of Fe3O4, SiO2, and Fe3O4@SiO2 NCs were prepared at a concentration of 75 mg / L to eliminate concentration-effect interference. The sterilized seeds were then placed in the different treatment solutions and soaked for 24 h at 25 ℃ in the dark, with a seed-to-treatment-solution volume ratio of 1:5. After soaking, the seeds were removed and their surface moisture was dried for subsequent germination experiments.

[0078] To evaluate the effects of different nanoparticle treatments on seed germination and seedling growth, the treated seeds are evenly placed in a sterile petri dish with a diameter of 9 cm. Two layers of filter paper are laid at the bottom of the petri dish, 25 seeds are placed in each dish, and 3 mL of equal volume of deionized water is added. Five replicates are set for each treatment. The petri dishes are cultured in an artificial climate incubator, the temperature is controlled at 25 ±1 °C, and the culture time is 7 d. The filter paper is kept moist during the test, and the same treatment solution is supplemented when necessary. The germination of seeds is counted regularly during the germination process. Wherein, the standard for seed germination is that the radicle breaks through the seed coat and its length reaches more than half of the seed length. The calculation formulas of germination potential and germination rate are as follows:

[0079] Germination potential = Number of normally germinated seeds within a specified period / Total number of test seeds × 100%.

[0080] Germination rate = Number of normally germinated seeds at the end of the test / Total number of test seeds × 100%.

[0081] Subsequently, the samples are dried in an oven at 75 °C to constant weight and weighed to obtain the dry weight per plant.

[0082] 2. Results

[0083] Compared with separate application of treatments, combined application of nanomaterials significantly improves seed germination and seedling growth performance. In terms of germination vigor ( Figure 10 A) and germination rate ( Figure 10 B), the Fe3O4@SiO2 treatment reaches the highest level, and is significantly higher than the separate application of Fe3O4 and SiO2 treatments. Among them, the Fe3O4 treatment is the lowest, and the SiO2 treatment is in the middle, showing an obvious gradient difference (Fe3O4<SiO2< Fe3O4@SiO2). Meanwhile, in terms of the dry weight ( Figure 10 C) indicator, the combined treatment also shows a higher accumulation level, indicating that it not only promotes the germination process, but further enhances the early biomass formation ability. In conclusion, the promotion effect of composite nanomaterials is significantly better than that of single materials, indicating that there is a synergistic effect between the two nano-components, thereby exerting a stronger physiological promotion effect in the seed germination and seedling growth stages.

[0084] Example 4: Alleviation effect of different concentrations of Fe3O4@SiO2 NCs on shoot and root phenotypes of wheat under drought stress

[0085] 1. Method

[0086] The test material was selected from the drought-resistant variety "Ruichun No. 1" previously screened by the applicant. Four treatments were set up: control (soil relative moisture content 75%–80%, root application of distilled water); 50 mg / L Fe3O4@SiO2NCs (soil relative moisture content 75%–80%, root application of 50 mg / L nano-solution); 75 mg / L Fe3O4@SiO2NCs (soil relative moisture content 75%–80%, root application of 75 mg / L nano-solution); and 100 mg / L Fe3O4@SiO2NCs (soil relative moisture content 75%–80%, root application of 100 mg / L nano-solution). The specific operational methods involved in this example are as follows:

[0087] Preparation of nanomaterials: Same as in Example 1.

[0088] Determination of aboveground phenotypes: On day 15 after treatment, aboveground morphological indicators of wheat plants were measured. Plant height was measured using a ruler from the cotyledon node to the terminal bud; stem diameter was measured using calipers; and leaf area was determined using the length-width ratio method. Each treatment was replicated five times. Relative chlorophyll content was measured using a SPAD photosynthetic pigment analyzer (SPAD-502; Konica Minolta, Tokyo, Japan), avoiding the leaf veins. Relative moisture content was determined by weighing. These measurements were based on the third functional leaf and were performed between 9:00 and 11:00. Subsequently, five wheat seedlings from each treatment were taken, divided into aboveground and underground portions, placed in kraft paper envelopes, and recorded. Samples were placed in a precision drying oven, set to 105 ℃ for 20 min for blanching, and then dried at 85 ℃ to constant weight. The aboveground dry weight and aboveground fresh weight were weighed and recorded.

[0089] Root system measurements: On day 15 after treatment, the root morphology of wheat plants was measured. Three plants were randomly selected from each treatment, and the roots were slowly rinsed along the edge of the pot until all soil adhering to the roots was removed. After rinsing, the above-ground parts of the wheat plants were cut off, and the roots were placed in an acrylic glass tank filled with clean water in multiple stages, with the roots fully spread out. Images were acquired using an EPSON V370 dual-light source scanner. Finally, the WinRHIZOReg2009c root analysis system was used to automatically analyze the acquired images, obtaining root morphology indicators such as total root length, average taproot length, number of lateral roots, maximum root width, maximum root depth, width-to-depth ratio, and convexity area.

[0090] 2. Results

[0091] The applicant systematically evaluated the mitigating effects of different concentrations of Fe3O4@SiO2NCs on the aboveground and root phenotypes of wheat under drought stress. Figure 11(A and 12A). The results showed that under drought stress, leaf area, plant height, SPAD, aboveground fresh weight, aboveground dry weight, and relative water content all decreased compared to the control treatment (CK) (P < 0.05). Figure 11 (BG). However, under drought stress, the values ​​of aboveground traits first increased and then decreased with increasing Fe3O4@SiO2NCs concentration. The maximum value was reached at a Fe3O4@SiO2NCs concentration of 75 mg / L. Compared with the drought + 50 mg / L Fe3O4@SiO2NCs treatment, the 75 mg / L Fe3O4@SiO2 treatment significantly increased these traits by 7.42%, 23.71%, 18.81%, 46.97%, 55.80%, and 49.44%, respectively (P < 0.05). Similarly, under drought treatment, total root length, average taproot length, number of lateral roots, maximum root width, maximum root depth, width-to-depth ratio, convexity area, root fresh weight, and root weight also showed similar trends (P < 0.05). Figure 12 (BJ). The above results indicate that 75 mg / LFe3O4@SiO2NCs can effectively improve the growth performance of wheat under drought stress, which can directly support subsequent mechanism research.

[0092] Example 5: Effects of Fe3O4@SiO2NCs on wheat structure and hormones under drought stress

[0093] 1. Method

[0094] Consistent with Example 4, the experiment included four treatments: control (soil relative moisture content 75%–80%, root application of distilled water); control + Fe3O4@SiO2NCs (soil relative moisture content 75%–80%, root application of 75 mg / L nano solution); drought (soil relative moisture content 50%–55%); and drought + Fe3O4@SiO2NCs (soil relative moisture content 50%–55%, root application of 75 mg / L nano solution). The specific operational methods involved in this example are as follows:

[0095] Preparation of nanomaterials: Same as in Example 1.

[0096] Anatomical structure determination: Root segments (approximately 0.5 cm) were collected on day 15 post-treatment at locations 3 cm, 6 cm, and 9 cm from the secondary root tip. These segments were preserved in 75% ethanol, and the presence of RCS in the cortex was phenotypically analyzed using acridine orange staining, a feasible method for assessing RCS. Acridine orange fluorescent cell nuclei were used for phenotypic analysis of the onset time of RCS in individual cortical layers. The disappearance of the cortex was determined by measuring the percentage of surviving cells, thus indicating the manifestation of RCS in the root cross-section. Acridine orange-stained root segments were embedded in gelatin capsules containing the Tissue-Tek CRYO-OCT complex (Thermo Fisher Scientific, Waltham, MA, USA), then rapidly frozen in liquid nitrogen, and subsequently stored at -20°C. Cross-sections (8 μm thick) of the embedded segments were cut using a cryostat (Leica CM1950) and imaged using a laser scanning confocal microscope (FV-1000, Olympus, Japan). The main measurements performed using the cross-sectional images included area determination and variable counting. The following regional measurements were obtained by pixel counting: total cross-sectional area and diameter, stem area and diameter, and cortical area and diameter. The number of acridine orange fluorescent cell nuclei was counted in all cell layers of the 8 μm thick sections. Count data included the number of cortical cell layers and the area of ​​cortical lacunar tissue. A control sample without RCS was obtained from root segments collected 3 cm from the root tip. The percentage of cortical senescence was calculated by comparing the cortical area at 3 cm from the root tip (total cross-sectional area - stem area) with the corresponding area at the sampling location.

[0097] Determination of endogenous abscisic acid (ABA) content: On day 15 after treatment, three pots of plants from each treatment were randomly selected and slowly rinsed along the edge of the pot until the soil attached to the roots was washed away. After rinsing, the above-ground parts of the wheat plants were cut off, and root segments (approximately 0.5 cm) were quickly collected at 3 cm, 6 cm, and 9 cm from the tip of the secondary roots. The ABA content in different root segments was determined using an Agilent 1260 high-performance liquid chromatograph and an Eclipse XDB-C18 column (250 mm × 4.6 mm, 5 μm, Agilent, California, USA). Briefly, 2 g of fresh root segments were mixed and ground in an ice bath with 10 mL of pre-cooled 80% methanol. The mixture was then centrifuged at 8000 g for 10 minutes at 4°C, the supernatant was collected, and the residue was resuspended in 8 mL of pre-cooled 80% methanol for another round of centrifugation and supernatant collection. The aqueous phase was then extracted three times with 20 mL of ethyl acetate. The sample was evaporated and dried at 40°C, and the ABA plant hormone was separated by gradient elution.

[0098] 2. Results

[0099] The results showed that drought treatment significantly increased root ABA content, cortical cavity area, and cortical senescence percentage; while Fe3O4@SiO2 NCs treatment significantly reduced drought-induced cortical cavity area and cortical senescence percentage. Figure 13 The key finding is that the effect of Fe3O4@SiO2 NCs on ABA content is not entirely synchronized with changes in RCS, suggesting that tissue-specific distribution or signal sensitivity remodeling of ABA may be more critical than changes in total ABA levels. This result provides direct preliminary evidence for further analysis of how Fe3O4@SiO2 NCs regulate wheat RCS through ABA signaling at the tissue-specific level in this project.

[0100] To verify the mitigation effect of Fe3O4@SiO2NCs on drought stress under field conditions, we conducted a yield verification experiment in Luyang Town, Jingtai County, Baiyin City, Gansu Province. Figure 14For both tested wheat varieties (Ruichun 1 and Dingxi 48), the treatments resulted in a significant decrease in yield. Specifically, compared to the control (CK), the yields of Ruichun 1 and Dingxi 48 under the DS treatment were significantly reduced by 21% and 23%, respectively (P < 0.05). The application of Fe3O4@SiO2NCs alone also had a certain promoting effect on wheat yield under the CK treatment. After applying the CK+Fe3O4@SiO2NCs treatment, the yields of Ruichun 1 and Dingxi 48 increased significantly by 4.36% and 2.69%, respectively, compared to the CK treatment (P < 0.05). More importantly, DS+Fe3O4@SiO2NCs effectively mitigated yield losses caused by drought. Compared to the DS treatment, the yields of Ruichun 1 and Dingxi 48 under the DS+Fe3O4@SiO2NCs treatment were significantly increased by 13.68% and 13.59%, respectively (P < 0.05). The above results indicate that Fe3O4@SiO2NCs have a stable yield-increasing effect on wheat under drought stress.

[0101] In summary, this invention provides the application of Fe3O4@SiO2 nanocomposites in promoting wheat seed germination and seedling growth under drought stress. The promoting effect of the Fe3O4@SiO2 nanocomposites is significantly better than that of the single material, indicating a synergistic effect between the two nanocomponents, thereby exerting a stronger physiological promoting effect during the seed germination and seedling growth stages. Simultaneously, Fe3O4@SiO2NCs can effectively improve the growth performance of wheat under drought stress, including increases in total root length, average taproot length, number of lateral roots, maximum root width, maximum root depth, width-to-depth ratio, convexity area, root fresh weight, and root weight. It can be used to prepare seed coating agents and plant growth promoters, showing broad application prospects.

[0102] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. Application of Fe3O4@SiO2 nanocomposites in promoting wheat seed germination under drought stress.

2. Application of Fe3O4@SiO2 nanocomposites in promoting wheat seedling growth under drought stress.

3. Application of Fe3O4@SiO2 nanocomposites in delaying wheat root senescence under drought stress.

4. Application of Fe3O4@SiO2 nanocomposites in improving wheat yield under drought stress.

5. The application as described in any one of claims 1-4, characterized in that, The Fe3O4@SiO2 nanocomposite material was prepared by the following method: (1) Fe3O4 NPs and Tween-60 were dispersed in cyclohexane by ultrasonic treatment; (2) After vortex mixing of the reaction solution obtained in step (1), add ammonium hydroxide to make a transparent brown solution; (3) After adding tetraethyl orthosilicate to the solution in step (2), react at room temperature, and precipitate Fe3O4@SiO2NCs with methanol, and collect by centrifugation.

6. A seed soaking agent for promoting wheat seed germination, characterized in that, The seed soaking agent contains Fe3O4@SiO2 nanocomposite material.

7. A wheat growth promoter, characterized in that, The growth promoter contains Fe3O4@SiO2 nanocomposite material.

8. A method for promoting wheat seed germination under drought stress, characterized in that, Includes the following steps: Select plump wheat seeds of uniform size, disinfect them with 5% sodium hypochlorite solution for 10 min, and then rinse them with deionized water to remove residual disinfectant. Place the disinfected seeds in Fe3O4@SiO2 nanocomposite material and soak them at 25℃ in the dark for 24 h. The seed mass to Fe3O4@SiO2 nanocomposite material volume ratio is 1:

5. After soaking, remove the seeds and dry the surface moisture for germination.

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