Detection method of inositol hexaphosphate and application of inositol hexaphosphate in plant cultivation

Abstract

The invention discloses a detection method of inositol hexaphosphate and application thereof in plant cultivation, the electrostatic and chelation effects of nano iron oxide and inositol hexaphosphate are utilized to induce aggregation of nano particles to cause color change or UV-Vis absorption peak shift (200-220 nm), the detection method is used for rapidly detecting the concentration of inositol hexaphosphate in soil or a nutrient solution, the detection limit is 0.1 mg / L, the detection time is short, and the detection result is accurate. Total time lt; the time is 10 minutes. The method comprises the steps of sample extraction, reaction and optical determination, and is suitable for field monitoring of phosphorus fixation and fertilizer quality control. The detection result can guide the application of the compound, the phosphorus utilization efficiency is improved by 20-30%, and the plant cultivation effect is enhanced (for example, the alfalfa yield is increased by 18%, and the growth period of rice is shortened by about 7 days). The method provided by the invention is suitable for soil phosphorus fixation monitoring.

Description

Technical Field

[0001] This invention belongs to the fields of agricultural nanotechnology and materials analysis, specifically relating to a method for detecting inositol hexaphosphate and its application in plant cultivation. Background Technology

[0002] Phosphorus is a key nutrient element for plant growth, but it is easily fixed or lost in soil or hydroponic systems, resulting in low utilization. Inositol hexaphosphate (IP6, phytic acid) is the main form of phosphorus storage in plants, releasing phosphates and promoting root development through the auxin signaling pathway. In existing technologies, although IP6 can serve as a phosphorus source and growth signaling molecule, it degrades rapidly in soil or hydroponic systems (releasing >85-90% within 7 days), leading to low phosphorus utilization (500 mg / L) and potentially causing excessive iron accumulation, resulting in phytotoxicity risks, oxidative stress, and phytotoxicity (chlorophyll reduction >15%). These challenges make it difficult for existing phosphorus-iron composite materials to simultaneously achieve slow phosphorus release, iron supplementation, and root signaling regulation in greenhouse cultivation, limiting yield increases in crops such as alfalfa, tomato, tobacco, and rice (<10%).

[0003] IP6 is a major component of organic phosphorus in soil, accounting for approximately 50-80% of total soil organic phosphorus. It primarily originates from plant residues, seeds, and organic fertilizers. In the soil environment, it does not exist stably in a free form but tends to bind with soil components, forming various complexed or adsorbed forms. This binding often leads to phosphorus immobilization, reducing its bioavailability and affecting plant uptake and soil phosphorus cycling. In existing technologies, the detection of inositol hexaphosphate content in matrices mainly relies on enzymatic colorimetry or ion chromatography, which suffers from drawbacks such as long processing time (>1 hour), expensive equipment, and inapplicability to on-site conditions. This invention utilizes a composite material as an optical nanoprobe, coupled with a UV-Vis spectrophotometer or colorimetric card, to achieve rapid and low-cost detection, solving the problem of phosphorus use efficiency monitoring. Summary of the Invention

[0004] Purpose of the invention: The technical problem to be solved by the present invention is to provide a method for detecting inositol hexaphosphate.

[0005] Another technical problem to be solved by the present invention is to provide the application of the detection method in plant cultivation, detection of phosphorus fixation in soil, fertilizer quality control or hydroponic nutrient analysis.

[0006] The technical problem that this invention also aims to solve is to provide a low-concentration (100 mg / L) environmentally friendly IP6-FeNPs complex that achieves phosphorus release control at 55-60% within 30 days and synergistically promotes root development by 20-25%.

[0007] Another technical problem to be solved by the present invention is to provide the application of the aforementioned inositol hexaphosphate-nano iron oxide complex in plant cultivation or preparation of plant growth promoters.

[0008] Technical Solution: To solve the above-mentioned technical problems, the present invention provides a method for detecting inositol hexaphosphate. The method utilizes nano-iron oxide to react with inositol hexaphosphate, and detects the concentration of inositol hexaphosphate in the sample based on the linear relationship between the absorbance of the reaction solution and the concentration of inositol hexaphosphate.

[0009] The detection method includes the following steps: (1) Add standard solutions of inositol hexaphosphate with different known concentrations to nano iron oxide suspension to react and measure absorbance, and establish a standard curve of absorbance versus inositol hexaphosphate solution concentration; (2) Add the test sample containing inositol hexaphosphate to the nano iron oxide suspension for reaction and measure the absorbance value. Substitute the absorbance value into the standard curve obtained in step (1) to obtain the concentration of inositol hexaphosphate in the test sample.

[0010] The final concentration of inositol hexaphosphate is 0.1~10 mg / L.

[0011] The concentration of the nano-iron oxide is 10~100 mg / L.

[0012] The samples to be tested include soil, nutrient solution, or plant tissue.

[0013] The absorbance value is measured by visually observing color changes or by UV-Vis.

[0014] The absorbance value of this invention is determined by quantifying the IP6 concentration in the following two ways: Semi-quantitative: Visually observe the color change of the solution, referring to the standard color card (pre-calibrated to a concentration range of 0.1~10 mg / L IP6), with an accuracy of ±10%.

[0015] Quantitative analysis: The absorption peak intensity at 200-220 nm was measured using a portable UV-Vis spectrophotometer, or the optical signal was recorded via a smartphone app (based on RGB color analysis). The IP6 concentration was calculated using the formula: C_IP6 = (A_sample - A_blank) / k, where A_sample is the sample absorbance, A_blank is the blank absorbance, and k is a calibration constant (established using a standard IP6 solution, with a linear range of FeNPs:IP6 mass ratio of 2~5:1). The measurement time was approximately 2 minutes.

[0016] The present invention also includes the application of the aforementioned method for detecting inositol hexaphosphate in soil phosphorus fixation, fertilizer quality control, or hydroponic nutrient analysis.

[0017] This invention also provides a portable detection device, costing approximately 50-100 USD per set, suitable for laboratory or field use. The device includes the following modules: (1) Extraction container: 5 mL centrifuge tube for extraction and shaking of matrix sample with acid solution, equipped with a sealing cap to prevent leakage.

[0018] (2) Reaction module: including dropper (for precise addition of FeNPs suspension, 0.5 mL / time) and small shaker (manual or electric, frequency 100-300 rpm) to ensure uniform reaction.

[0019] (3) Detection module: Includes a portable UV-Vis spectrophotometer (wavelength range 190~400 nm, accuracy ±0.01AU) or a smartphone stand (equipped with an LED light source, wavelength 400-700 nm, for color analysis). The smartphone app captures RGB values ​​through the camera, combines them with a preset calibration curve, and outputs the IP6 concentration.

[0020] (4) Auxiliary components: microfilter (0.45 μm, for extract clarification), reagent bottle (for storing FeNPs suspension, light-proof design), and waste collection tank (meeting environmental protection requirements). The device is compact (approximately 20 cm x 10 cm x 10 cm), weighs less than 1 kg, and can be battery powered, making it suitable for on-site operation. All components are made of corrosion-resistant materials (such as polypropylene and glass) to ensure long-term stability.

[0021] The present invention also includes an inositol hexaphosphate-nano iron oxide composite, the composite comprising nano iron oxide with a particle size of 10-50 nm and inositol hexaphosphate loaded on its surface through electrostatic and chelating interactions, wherein the mass ratio of nano iron oxide to inositol hexaphosphate is 2-5:1, which can ensure sufficient chelation without causing excessive IP6 to cause aggregation or reduced stability.

[0022] The present invention also includes a method for preparing an inositol hexaphosphate-nano iron oxide composite, comprising the following steps: (1) Synthesis of FeNPs: FeNPs with a particle size of 10~50 nm were synthesized by coprecipitation method; (2) FeNPs functionalization: FeNPs were dispersed in deionized water to obtain FeNPs solution, ultrasonic treatment was performed, pH was adjusted, citric acid was added, and after reaction, the solution was centrifuged and washed before being dispersed in deionized water. (3) IP6 loading: Functionalized FeNPs were added to the IP6 solution, ultrasonicated and stirred, centrifuged and washed, and freeze-dried to obtain IP6-FeNPs powder.

[0023] The specific steps in step (1) are as follows: FeCl2·4H2O and FeCl3·6H2O are dissolved in deionized water, heated under nitrogen protection, NH4OH is added dropwise, stirred, black Fe3O4 precipitate is collected, washed and vacuum dried to obtain FeNPs with a particle size of 10~50nm.

[0024] In step (2), the mass ratio of FeNPs solution to citric acid is 8:1 to 12:1.

[0025] In step (2), the pH is 5.0 to 6.0.

[0026] In step (3), the mass ratio of the IP6 solution to the functionalized FeNPs is 0.2:1 to 0.5:1.

[0027] In step (3), the ultrasonic power is 80~120 W, the ultrasonic frequency is 30~50 kHz, the ultrasonic time is 5~15 min, the freeze-drying temperature is -40~-60°C, and the freeze-drying time is 20~30 h.

[0028] The present invention also includes the application of the aforementioned inositol hexaphosphate-nano iron oxide complex in plant cultivation or the production of plant growth promoters, wherein the plants include one or more of alfalfa, tomato, or tobacco.

[0029] The cultivation includes soil cultivation or hydroponics.

[0030] Mechanism of the invention: The six phosphate groups (-PO4) of IP6 3- Fe on the surface of functionalized FeNPs is adsorbed and chelated by electrostatic adsorption and chelation. 3+ / Fe 2+ Ions form Fe-OP bonds (FTIR confirmed at 600 cm⁻¹) -1 The core-shell structure is constructed to achieve nanoscale encapsulation with IP6. Citric acid functionalization introduces carboxyl groups (-COOH), adjusting the zeta potential to -25 mV, improving dispersibility and preventing oxidation. In application, the complex slowly hydrolyzes and releases phosphorus at pH 5.0-6.0 (35% at 14 days, 55-60% at 30 days). Phosphate activates the plant PI3K signaling pathway, promoting root elongation and lateral root differentiation (root length +20%, lateral root +25%). Simultaneously, a low dose of Fe... 2+ / Fe 3+Iron supplementation (<0.1 mg / L) enhances the activity of photosynthetic enzymes (such as Rubisco) (Fv / Fm +10%) and antioxidant enzymes (SOD +15%), shortening the reproductive period by 3 days. This synergistic effect is superior to single IP6 or FeNPs, innovatively combining phosphorus slow release with iron signal regulation, improving utilization efficiency by 20-30%. The detection method described in this invention utilizes the six phosphate groups (-PO4) of IP6. 3- The electrostatic and chelating interactions between FeNPs and functionalized nano-iron oxides (FeNPs, particle size 10–50 nm, surface modified with citric acid, Zeta potential approximately -25 mV) form stable Fe-OP bonds (confirmed by Fourier transform infrared spectroscopy, characteristic peak at 600 cm⁻¹). -1 This chelation reaction alters the surface charge of FeNPs, leading to particle aggregation and subsequent changes in optical signals, including a change in solution color from brownish-red to dark brown or an increased intensity of the absorption peak at 200-220 nm in the UV-Vis spectrum. These optical changes can be semi-quantitatively or quantitatively analyzed by visual observation, a portable UV-Vis spectrophotometer, or a smartphone application (App). The detection method of this invention synergistically enhances phosphorus utilization efficiency when applied to plant cultivation. The detection method provides precise guidance for the application of the IP6-FeNPs complex by rapidly determining the IP6 concentration in the substrate. For example, in soil cultivation, the IP6 level in the substrate can be detected first to determine whether the complex (100 mg / L) needs to be supplemented to maintain a stable phosphorus supply; in hydroponics, the IP6 concentration in the nutrient solution can be detected to optimize the application rate to promote rice root development (20% increase in root length and 25% increase in lateral root number). Therefore, this detection mechanism can be further applied to the preparation of FeNPs-IP6 complexes, whose chelation mechanism involves the phosphate groups of IP6 reacting with the Fe6 groups on the surface of FeNPs. 3+ / Fe 2+ Fe-OP bonds are formed (FTIR 600 cm⁻¹) -1 The peak), changing the zeta potential (shifted from -25 mV), causes particle aggregation, generating a measurable optical signal. This signal is positively correlated with IP6 concentration (UV-Vis absorption peak intensity increases with concentration), and this was verified by DLS (particle size increase) and SEM (root adsorption observation).

[0031] Beneficial Effects: Compared with existing technologies, this invention provides a method for the rapid determination of inositol hexaphosphate (IP6) concentration in soil, nutrient solutions, or plant tissue matrices. This method has high sensitivity, with a detection limit for IP6 as low as 0.1 mg / L, superior to enzymatic methods (approximately 40 mg / L), and a total detection time of less than 10 minutes. Compared with traditional enzymatic colorimetric or ion chromatography methods, it shortens the time by 70% compared to traditional methods (>1 hour), and requires no complex pretreatment or expensive equipment. Using a UV-Vis spectrophotometer or colorimetric card, it reduces costs by 90% compared to ion chromatography equipment (>10,000 USD), making it suitable for rapid on-site monitoring; it is environmentally friendly, non-toxic, and does not cause environmental pollution. The detection results of this invention can guide the application of compound fertilizers, improving phosphorus use efficiency by 20-30% and enhancing plant cultivation effects (e.g., increasing alfalfa yield by 18% and shortening the rice growth period by approximately 7 days). The method of this invention is applicable to soil phosphorus fixation monitoring, fertilizer quality control, and hydroponic nutrient analysis, and can be further developed into test strips for simplified operation. The complex prepared in this invention, when added at a concentration of 100 mg / L inositol hexaphosphate-nano iron oxide complex in soil culture, promotes the fresh weight and yield of alfalfa, tomato, and tobacco. Simultaneously, when added at a concentration of 100 mg / L in Kimura B nutrient solution in hydroponics, it promotes root development in rice (root length increases by 20%, lateral root number increases by 25%) through 35% phosphorus release and root adsorption within 14 days, and shortens the growth period by 3 days. Attached Figure Description

[0032] Figure 1 UV-Vis spectrum (curve) for IP6.

[0033] Figure 2 This is a color change graph for IP6 detection.

[0034] Figure 3 Phenotypic diagram of seedlings grown in soil.

[0035] Figure 4 Phenotypic chart of hydroponically grown rice over three weeks. Detailed Implementation

[0036] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0037] Example 1: FeNPs-based method for detecting inositol hexaphosphate This embodiment describes a method for rapid detection of inositol hexaphosphate (IP6) concentration in soil matrix. This method utilizes the chelation reaction between functionalized FeNPs and IP6 to induce particle aggregation and optical changes, enabling on-site quantitative analysis.

[0038] 1. Preparation of FeNPs suspension: (1) FeNPs synthesis: Dissolve 0.02 mol FeCl2·4H2O and 0.04 mol FeCl3·6H2O in 100 mL of deionized water (Fe 2+ Fe 3+ = 1:2). Under nitrogen protection, heat to 80°C, add 10 mL of 25% NH4OH dropwise, and stir at 800 rpm for 30 minutes. Collect the black Fe3O4 precipitate, wash, and vacuum dry at 60°C. DLS (Malvern Zetasizer Nano ZS) analysis revealed FeNPs with a particle size of 10–50 nm.

[0039] (2) Functionalization of FeNPs: Disperse 1 g of FeNPs in 100 mL of deionized water and treat with ultrasound (100 W, 40 kHz, 15 min).

[0040] Adjust the pH to 5.5, add 0.1 g citric acid, and stir at 25°C for 2 hours (300 rpm). Centrifuge (10,000 rpm, 10 minutes), wash, and disperse in deionized water to prepare a 100 mg / L FeNPs suspension (Zeta potential -25 mV), and store in the dark for later use.

[0041] 2. Sample extraction: Take 1 g of soil matrix (peat:vermiculite:perlite = 2:1:1, organic matter 320.13 g / kg, initial phosphorus content 7.28 g / kg), add 5 mL of 0.1 M hydrochloric acid (HCl) solution (pH adjusted to 5.5), and manually shake for 1 minute (300 rpm). Then centrifuge (10,000 rpm, 1 minute) or filter through a 0.45 μm membrane to obtain a clear extract. This step achieves an extraction efficiency >90% and minimizes interfering substances.

[0042] 3. Establish a standard curve Different concentrations of IP6 solutions (sodium phytate, pH 5.5, Maclean Chemical Reagent, CAS No.: 14306-25-3) were prepared, and 0.5 mL of FeNPs suspension was added to achieve final IP6 concentrations of 0, 0.1, 1, 5, and 10 mg / L in the reaction system. Manual shaking for 10 seconds promoted the adhesion of IP6 phosphate groups to FeNPs on the FeNPs surface. 3+ / Fe 2+ Fe-OP bond formation (FTIR confirmed at 600 cm⁻¹) -1After the reaction, the solution color gradually changed from brownish-red to dark brown. Particle aggregation led to an enhancement of the UV-Vis absorption peak (200-220 nm). Measurements of the absorbance yielded the linear equation: A = 0.18 × C_IP6 + 0.1(R0). 2 =0.98, where A is the absorbance value and C_IP6 is the concentration of IP6. C_IP6 = (A_sample - A_blank) / 0.18, where A_sample is the sample absorbance value and A_blank is the blank absorbance value (approximately 0.1 AU). See Table 1 for results. Figure 1 .

[0043] Table 1: UV-Vis absorbance and calculated concentration at different IP6 concentrations

[0044] Note: Data are mean ± standard deviation (n=3 replicates). Accuracy is calculated as (calculated concentration / standard concentration) × 100%. Overall accuracy is 95–105%, and linearity ranges from 0.1 to 10 mg / L.

[0045] From Table 1 and Figure 2 It can be seen that as the concentration of IP6 increases, the absorbance increases linearly (the peak intensity at 210 nm increases from 0.1 AU to 2.0 AU), and the color changes from light brownish-red (RGB 200,100,50) to dark brown (RGB 80,40,25).

[0046] 4. Actual soil sample testing Add 0.5 mL of FeNPs suspension to 1 mL of the extract obtained in step 2, and shake manually for 10 seconds to promote the adhesion of IP6 phosphate groups to Fe on the FeNPs surface. 3+ / Fe 2+ Fe-OP bond formation (FTIR confirmed at 600 cm⁻¹) -1 After the reaction, the solution color gradually changed from brownish-red to dark brown, and particle aggregation led to an enhancement of the UV-Vis absorption peak (200-220 nm). The absorbance of the reaction solution in the 200-220 nm range was measured using a UV-Vis spectrophotometer. The IP6 concentration was calculated by referring to the standard curve established in step 3. In actual soil sample testing, the IP6 concentration of the extract was approximately 2.5 mg / L, consistent with the results of the enzymatic colorimetric method (deviation <5%).

[0047] Iron safety: Fe release during the reaction is <0.1 mg / L, which is below the toxicity threshold (>10 mg / L), and there is no environmental risk.

[0048] In summary, this detection method, through the FeNPs-IP6 chelation mechanism, achieves rapid and accurate analysis, superior to traditional methods (70% reduction in time and 20% reduction in cost), and can guide the application of the compound (e.g., optimizing the 100 mg / L addition amount in phosphorus-fixed soils). The detection limit in this embodiment is 0.1 mg / L, and the total time is less than 10 minutes, making it suitable for monitoring phosphorus fixation in soil.

[0049] Example 2 Preparation of IP6-FeNPs complex 1. FeNPs synthesis: Dissolve 0.02 mol FeCl2·4H2O and 0.04 mol FeCl3·6H2O in 100 mL of deionized water (Fe 2+ Fe 3+ = 1:2). Under nitrogen protection, heat to 80°C, add 10 mL of 25% NH4OH dropwise, and stir (800 rpm) for 30 minutes. Collect the black Fe3O4 precipitate, wash, and vacuum dry at 60°C. DLS (Malvern Zetasizer Nano ZS) analysis revealed FeNPs with a particle size of 10–50 nm.

[0050] 2. FeNPs functionalization: Disperse 1 g of FeNPs in 100 mL of deionized water and treat with ultrasound (100 W, 40 kHz, 15 min).

[0051] Adjust the pH to 5.5, add 0.1 g citric acid, and stir at 25°C for 2 hours (300 rpm). Centrifuge (10,000 rpm, 10 minutes), wash, and disperse in 50 mL deionized water to obtain a functionalized FeNPs suspension.

[0052] 3. Loading IP6: Prepare 50 mL of 0.01 M IP6 solution (sodium phytate, pH 5.5). Add 1 g dry weight of functionalized FeNPs suspension (approximately 45 mL), sonicate (100 W, 40 kHz, 10 min), and stir for 24 h (400 rpm, 25°C). Centrifuge (10,000 rpm, 15 min), wash, and freeze-dry (-50°C, 24 h) to obtain IP6-FeNPs powder. Characterization: UV-Vis determination showed an IP6 loading efficiency of 85% (loading efficiency was determined by UV-Vis: initial IP6 concentration (A0, 200-220 nm absorption peak) minus supernatant concentration (A1), efficiency = (A0 - A1) / A0 × 100% = 85%); FTIR (Thermo Fisher Nicoleti S50) confirmed PO (1000-1100 cm⁻¹). -1 ) and Fe-OP (600 cm -1 () bond; Zeta potential -25 mV; DLS (Malvern Zetasizer Nano ZS) shows particle size of 10-50 nm, and uniform coating.

[0053] Example 3: Application of IP6-FeNPs in Soil-grown Plants 1. Matrix preparation and experimental design: The substrate consisted of peat moss:vermiculite:perlite in a ratio of 2:1:1 (initial organic matter 320.13 g / kg, P 7.28 g / kg, K 1.73 g / kg, N 7.43 g / kg). Alfalfa, tomato (mini-tomato), and tobacco (NC89) were planted on the substrate.

[0054] The experimental groups included: Experimental group: Prepare a 100 mg / L IP6-FeNPs solution (with an IP6 concentration of 30 mg / L) (IP6-FeNPs group). Spray different plants with the IP6-FeNPs solution weekly at a concentration of 200 mL / kg substrate.

[0055] Control group: Free IP6 (30 mg / L IP6) solution (IP6 group) was prepared and sprayed on different plants weekly at a concentration of 200 mL / kg substrate; unloaded nano iron oxide (FeNPs, sprayed on different plants weekly at 80 mg / kg) (FeNPs group) and blank substrate (no additional phosphorus source, CK group).

[0056] Experimental conditions: Greenhouse temperature 22–25°C, humidity 60%, photoperiod 16 hours light / 8 hours dark, light intensity 200 µmol·m-2 ·s -1 Water 200 mL / kg substrate (pH 6.0) weekly. Growth cycle: alfalfa 5 weeks, tomato and tobacco 8 weeks. See Table 2 for experimental results. Figure 3 .

[0057] Table 2

[0058] Note: Data are mean ± standard deviation (n=5 replicates). Different lowercase letters (a, b) indicate significant differences between groups. p <0.05, based on ANOVA test and Tukey post-hoc multiple comparisons). p The value represents the significance level of the difference between groups in the overall population. p Values ​​are rounded to two decimal places, with 0 indicating p < 0.01. The percentages in parentheses represent the relative increase compared to the CK group (for reference only and not included in the statistics).

[0059] From Table 2 and Figure 3 It can be seen that, in terms of the fresh weight of the above-ground parts: alfalfa ( Figure 3 a): The fresh weight of the aboveground parts of the IP6-FeNPs group (2.0g) was significantly higher than that of the control group in all three treatments. p <0.05, no significant difference was found between the IP6, FeNPs group and the blank matrix group. Tomato ( Figure 3 (b) The fresh weight of the aboveground parts of the IP6-FeNPs group (14.4g) was significantly higher than that of the control group in all three treatments. p <0.05), no significant differences were found between the IP6, FeNPs group and the blank matrix group; tobacco ( Figure 3 c): The fresh weight of the aboveground parts of the IP6-FeNPs group (10.3g) was significantly higher than that of the control group in all three treatments. p<0.05), there were no significant differences among the IP6 group, FeNPs group, and blank substrate group. In terms of yield: Tomato: The fruit yield in the IP6-FeNPs group was 115 g, significantly higher than the three control treatments. Alfalfa: The dry matter yield in the IP6-FeNPs group was 1.18 g, significantly higher than the three control treatments. Tobacco had no fruit yield; the leaf area in the IP6-FeNPs group was 48 cm², significantly higher than the three control treatments. Phosphorus content: The phosphorus content in the leaves of the IP6-FeNPs group was significantly increased. Iron content: The iron content in the leaves of both the IP6-FeNPs and FeNPs groups increased. Phosphorus use efficiency: The IP6-FeNPs group showed a significant increase of 20-25%; free IP6 and the blank substrate group showed no significant increase. Substrate nutrients: The final phosphorus content in the substrate of the IP6-FeNPs group was 4.28 g / kg, while the phosphorus content in the free IP6 and blank substrate groups was <0.01 g / kg, reflecting phosphorus loss due to rapid release of free IP6 (>85% after 7 days). Iron safety: The iron release from the matrix solution of the IP6-FeNPs group was <0.1 mg / L, which is below the toxicity threshold (>10 mg / L).

[0060] In summary, IP6-FeNPs significantly improved the fresh weight and yield of soil-grown plants through slow-release phosphorus and low-dose iron supplementation, while free IP6 showed no difference from the blank substrate due to rapid release.

[0061] Example 4: Application of IP6-FeNPs in hydroponic rice cultivation 1. Experimental Design: Plants: Rice (Nipponbare, Japan) Oryza sativa cv. Nipponbare).

[0062] Hydroponic conditions: Kimura B nutrient solution (basal phosphorus content 0.36 mM, approximately 11 mg / LP, Jiangxi Qiyun Biotechnology, product number: QM4003), temperature 25-28°C, humidity 60%, photoperiod 16 hours light / 8 hours dark, light intensity 200 µmol·m -2 ·s -1 .

[0063] Treatment group: Experimental group: Nutrient solution with a final concentration of 100 mg / L IP6-FeNPs (final concentration of 30 mg / L IP6). Control group: Nutrient solution with free IP6 (final concentration of 30 mg / L), unloaded nano-iron oxide (final concentration of FeNPs, 80 mg / L), and blank (CK, Kimura B nutrient solution only).

[0064] The experimental conditions were as follows: the nutrient solution was changed every 2 weeks, maintaining a pH of 5.0-5.5. The growth cycle was 6 weeks (from the vegetative growth stage to the tillering stage). The experimental results are shown in Table 3 and... Figure 4 .

[0065] Table 3

[0066] Data are presented as mean ± standard deviation (n=5 replicates). Different lowercase letters (a, b, c) indicate significant differences between groups (p<0.05, based on Tukey post-hoc multiple comparisons after ANOVA test). The ANOVA p-value represents the significance level of the overall difference between groups. p-values ​​are rounded to two decimal places, with 0.00 indicating p<0.01. The percentages in parentheses represent relative increases compared to the control group (for reference only and not statistically significant).

[0067] From Table 3 and Figure 4 In terms of root development: compared with the control (CK), the IP6-FeNPs group showed a 20% increase in root length (14.3 cm vs. 11.9 cm) and a 25% increase in the number of lateral roots (18 vs. 15). Compared with the CK, the free IP6 group showed a 10% increase in root length (13.1 cm) and a 12% increase in the number of lateral roots (16). Compared with the CK, the FeNPs group showed no significant increase in root length or the number of lateral roots (11.9 cm, 15). Regarding the growth period: compared with the CK, the IP6-FeNPs group had a 7-day earlier tillering stage (26 days vs. 33 days); other treatments showed no significant changes compared to the CK. Regarding biomass: compared with the CK, the IP6-FeNPs group showed an 18% increase in aboveground fresh weight (3.8 g vs. 3.2 g); other treatments showed no significant changes compared to the CK. Regarding phosphorus content: Compared with the control (CK), the root phosphorus content of the IP6-FeNPs group increased by 25% (0.34% vs. 0.27%), and the leaf phosphorus content increased by 20% (0.31% vs. 0.26%); other treatments showed no significant changes compared with the control (CK). Regarding iron content: Compared with the control (CK), the leaf iron content of both the IP6-FeNPs group and the FeNPs group increased, with a significant change compared with the control (CK). Regarding photosynthetic efficiency: Compared with the control (CK), the Fv / Fm value of the IP6-FeNPs group increased by 10% (0.83 vs. 0.75); other treatments showed no significant changes compared with the control (CK). Regarding iron safety: The iron release from the nutrient solution in the IP6-FeNPs group was <0.1 mg / L, below the toxicity threshold (>10 mg / L). Changing the nutrient solution every 2 weeks further reduced the risk of accumulation.

[0068] Significance of slow release: The IP6-FeNPs group released 35% phosphorus within 14 days, >95% compared to the free IP6 group, providing a stable phosphorus supply; SEM observation confirmed that the nanoparticles were adsorbed on the root surface, forming a local slow-release microenvironment. Nanotreatment enables the slow release of phosphorus from IP6, improving IP6 utilization efficiency by 20-25% and cost-effectiveness, while reducing phosphorus loss from the nutrient solution.

[0069] In summary, IP6-FeNPs, through short-term slow release, root adsorption, and iron supplementation, are significantly superior to free IP6 and the control, promoting root development and shortening the growth period of rice.

Claims

1. A method for detecting inositol hexaphosphate, characterized in that, The detection method utilizes the reaction of nano-iron oxide with inositol hexaphosphate, and detects the concentration of inositol hexaphosphate in the sample based on the linear relationship between the absorbance of the reaction solution and the concentration of inositol hexaphosphate.

2. The method for detecting inositol hexaphosphate according to claim 1, characterized in that, Includes the following steps: (1) Add standard solutions of inositol hexaphosphate with different known concentrations to nano iron oxide suspension to react and measure absorbance, and establish a standard curve of absorbance versus inositol hexaphosphate solution concentration; (2) Add the test sample containing inositol hexaphosphate to the nano iron oxide suspension for reaction and measure the absorbance value. Substitute the absorbance value into the standard curve obtained in step (1) to obtain the concentration of inositol hexaphosphate in the test sample.

3. The method for detecting inositol hexaphosphate according to claim 2, characterized in that, The final concentration of inositol hexaphosphate is 0.1~10 mg / L.

4. The method for detecting inositol hexaphosphate according to claim 2, characterized in that, The concentration of the nano-iron oxide is 10~100 mg / L.

5. The method for detecting inositol hexaphosphate according to claim 2, characterized in that, The samples to be tested include soil, nutrient solution, or plant tissue.

6. The method for detecting inositol hexaphosphate according to claim 2, characterized in that, The absorbance value was determined by visually observing color changes or by UV-Vis.

7. The application of the method for detecting inositol hexaphosphate according to any one of claims 1 to 6 in plant cultivation, detection of phosphorus fixation in soil, fertilizer quality control or hydroponic nutrient analysis.

8. An inositol hexaphosphate-nano iron oxide composite, characterized in that, The composite comprises iron oxide nanoparticles with a particle size of 10-50 nm and inositol hexaphosphate loaded on its surface through electrostatic and chelation interactions, wherein the mass ratio of the iron oxide nanoparticles to inositol hexaphosphate is 2-5:

1.

9. The application of the inositol hexaphosphate-nano iron oxide complex of claim 8 in plant cultivation or preparation of plant growth promoters, wherein the plant includes one or more of alfalfa, tomato, or tobacco.

10. The application according to claim 9, characterized in that, The cultivation includes soil cultivation or hydroponics.

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