Microplastic polluted area crop screening method based on root system type and morphological concentration

Abstract

The invention discloses a micro-plastic polluted area crop screening method based on root type and morphological concentration, which comprises the following steps: respectively sowing taproot system and fibrous system crop seeds in a plurality of control group soil with powdery polyethylene micro-plastic gradient concentration, flaky PE-MPs gradient concentration and no PE-MPs for cultivation and planting; various growth and physiological indexes of crops in a culture period are measured, and a correlation between concentration gradients of MPs in different forms and the suitability of plant root system types is constructed, so that crops suitable for planting in a micro-plastic polluted area are screened out. According to the method disclosed by the invention, PE-MPs (powdery and flaky) in different forms are determined to be selected in crops with different concentrations, and the pertinence is strong; the crop adaptability is determined by measuring the two-dimensional indexes of the crop growth index and the physiological index, and the accuracy is high; the method can be directly reused through a standardized process, can be quickly judged only by measuring key indexes during field application, and is good in application effect and high in operability.

Description

Technical Field

[0001] This invention relates to the fields of agricultural environmental remediation and crop cultivation technology, specifically a method for screening crops in microplastic-polluted areas based on root type and morphological concentration. Background Technology

[0002] Microplastics (MPs) can affect plant germination, growth, photosynthesis, and oxidative stress responses directly or indirectly. The roots are most significantly affected by MPs, followed by leaves, young shoots, and stems. The initial stage of MPs' action on plants involves adsorption onto the surface of seeds and roots, blocking root hair pores and altering the plant's absorption of substances such as water. They then enter the plant body through the roots, ultimately affecting growth indicators such as plant height and biomass.

[0003] In current agricultural production, polyethylene (PE) is widely used in mulch film, drip irrigation pipes and other products due to its low cost and excellent performance. The PE-MPs produced by its degradation have the highest accumulation in farmland soil (accounting for 26.2% of the total soil microplastics). Moreover, it is chemically inert and difficult to degrade naturally, posing a long-term threat to soil and plant growth.

[0004] Existing research focuses only on the effects of MPs on single crops or specific indicators, without combining differences in crop root types (such as taproots and fibrous roots) with concentration gradients of different forms of MPs to establish a compatibility relationship. It also lacks unified screening criteria and quantitative indicators, and cannot provide clear guidance for the selection of suitable crops for soils contaminated with different forms of MPs. Summary of the Invention

[0005] The purpose of this invention is to provide a method for screening crops in microplastic-polluted areas based on root type and morphological concentration, so as to solve the above-mentioned defects.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] The crop screening method for microplastic-polluted areas based on root type and speciation concentration proposed in this invention includes the following steps:

[0008] S1. Material preparation: Prepare polyethylene microplastics (PE-MPs), including powdered PE-MPs and flake PE-MPs. Select seeds of taproot and fibrous root crops, collect and pre-treat crop planting soil, and set aside for later use.

[0009] S2. Preparation of microplastic planting environment: Powdered PE-MPs and flake PE-MPs were mixed into the treated crop planting soil at multiple gradient concentrations to form several treatment groups; at the same time, a control group CK was set up with crop planting soil without added PE-MPs; the crop planting soil of the above treatment groups and 1 control group were placed in several pots for later use.

[0010] S3. Trial cultivation: Take several flowerpots containing soil for several treatment groups and one control group of crops, respectively. Sow taproot seeds in half of them and fibrous root crop seeds in the other half. After emergence, thin out the seedlings in each group. Then, cultivate them under suitable cultivation conditions.

[0011] S4. Index Measurement: The growth and physiological indicators of the taproot and fibrous root crops tested in step S3 were measured during the cultivation period.

[0012] S5. Data Analysis: Using the data indicators obtained in step S4, construct the correlation between the concentration gradient of different forms of MPs and the adaptability of plant root types, thereby screening out suitable crops for planting in microplastic-polluted areas.

[0013] Preferably, in step S1, the particle size of the powdered PE-MPs is 120μm to 180μm; the sheet-like PE-MPs are cut from polyethylene sheets with a thickness of 0.3mm and have a particle size ≤5mm.

[0014] Preferably, in step S1, the taproot crop seed is lettuce seed; the fibrous root crop seed is wheat seed.

[0015] Preferably, in step S1, the pretreatment measures for the crop planting soil are as follows: after being air-dried at room temperature, it is passed through a 5mm sieve and thoroughly mixed; the initial physicochemical properties of the crop planting soil are: ammonium nitrogen 4.83mg / kg, nitrate nitrogen 2.29mg / kg, pH 7.78, electrical conductivity 194μS / cm, organic carbon 0.56%, total nitrogen 0.037%, and carbon-nitrogen ratio 15.28.

[0016] Preferably, in step S2, the multiple gradient concentrations are as follows: powdered PE-MPs or flake PE-MPs are 0.02%, 0.2%, and 2% of the dry weight of the soil, respectively.

[0017] Preferably, in step S4, the determination of crop growth indicators includes: recording the germination rate, i.e., continuously recording the number of germinations after sowing until the data is stable; measuring the crop height and stem diameter periodically; and separating the above-ground part and the root at harvest time, and measuring the fresh weight of the above-ground part, the dry weight of the above-ground part, the fresh weight of the root, and the dry weight of the root respectively.

[0018] Preferably, in step S4, the determination of crop physiological indicators includes: determining leaf chlorophyll content using spectrophotometry; determining superoxide dismutase activity using the nitroblue tetrazolium photoreduction method; determining catalase activity using ultraviolet spectrophotometry; determining malondialdehyde content using the thiobarbituric acid method; quantitatively determining glutamine synthase activity using a spectrophotometer; and determining the direction of sucrose synthase decomposition, the direction of sucrose synthase synthesis, and the activity of sucrose phosphate synthase using a Greens reagent kit. For soil physicochemical indicators and enzyme activity determination, pH and conductivity are measured using a pH / conductivity meter; nitrate nitrogen and ammonium nitrogen content are determined using a potassium chloride extraction method; total carbon, total nitrogen, and C / N ratio are determined using an elemental analyzer; and high-throughput sequencing is used to analyze changes in microbial community composition, diversity, and functional genes.

[0019] The beneficial effects of this invention are as follows:

[0020] This invention provides a crop screening method for microplastic-polluted areas based on root type and morphological concentration. It clarifies the crop selection for different PE-MPs at different concentration gradients, making it highly targeted. The method uses two dimensions of crop growth and physiological indicators to determine crop suitability with high accuracy. The standardized process (fixed concentration gradient, culture conditions, and measurement methods) allows for direct reuse. In field applications, only key indicators (such as plant height, root dry weight, and GS activity) need to be measured for rapid determination, resulting in good application effects and strong operability. Attached Figure Description

[0021] Figure 1 This is a growth trend diagram of lettuce and wheat according to an embodiment of the present invention.

[0022] Figure 2 The above-ground and below-ground parts and roots of lettuce and wheat are shown in the following diagrams, along with their fresh and dry weights and chlorophyll content, according to embodiments of the present invention.

[0023] Figure 3 The graph shows the pH value, electrical conductivity, organic carbon, and C / N data of the rhizosphere soil of lettuce and wheat in embodiments of the present invention.

[0024] Figure 4 This is a graph showing the nitrate nitrogen, ammonium nitrogen, and nitrogen content data of the rhizosphere soil of lettuce and wheat in embodiments of the present invention;

[0025] Figure 5 The graph shows the data of sucrase, dehydrogenase, urease and catalase activities in the rhizosphere soil of lettuce and wheat, according to embodiments of the present invention.

[0026] Figure 6 This is a diagram showing the OTU composition and bacterial community diversity of the rhizosphere soil bacteria and fungi of lettuce according to an embodiment of the present invention.

[0027] Figure 7This is a diagram showing the variation of the rhizosphere soil fungal community in lettuce according to an embodiment of the present invention.

[0028] Figure 8 This is an embodiment of the present invention showing the OTU composition and bacterial community heatmap of wheat rhizosphere soil bacteria.

[0029] Figure 9 This is a diagram showing the composition of OTUs and the variation of fungal community diversity in the wheat rhizosphere soil according to an embodiment of the present invention.

[0030] Figure 10 This is a diagram showing the intergroup differences in the diversity of β-genes related to carbon and nitrogen metabolism in the rhizosphere soil microbial community of lettuce according to an embodiment of the present invention.

[0031] Figure 11 This is a diagram illustrating the functional gene analysis related to carbon and nitrogen metabolism in the rhizosphere soil of lettuce, according to an embodiment of the present invention.

[0032] Figure 12 This is a differential gene diagram of the experimental group and the control group of lettuce rhizosphere soil nitrogen metabolism-related functional genes in an embodiment of the present invention;

[0033] Figure 13 This is a diagram showing the intergroup differences in the β diversity of carbon and nitrogen metabolism functional genes in the wheat rhizosphere soil microbial community according to an embodiment of the present invention.

[0034] Figure 14 This is a diagram illustrating the analysis of functional genes related to carbon and nitrogen metabolism in wheat rhizosphere soil according to an embodiment of the present invention.

[0035] Figure 15 This is a partial least squares path modeling analysis diagram of microplastic concentration and speciation, soil nutrients, microorganisms, soil enzyme activity, plants, and plant growth in the lettuce and wheat systems of this invention. Detailed Implementation

[0036] The present invention will be further described below with reference to the embodiments. It should be noted that these are merely examples and descriptions of the inventive concept. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the inventive concept or exceed the scope defined in the claims, they should all be considered to fall within the protection scope of the present invention.

[0037] Example 1:

[0038] The crop screening method for microplastic-polluted areas based on root type and speciation concentration proposed in this invention includes the following steps:

[0039] S1. Material Preparation:

[0040] Polyethylene microplastics (PE-MPs) were prepared, including powdered PE-MPs and flake PE-MPs. The powdered PE-MPs, with a particle size of 120 μm to 180 μm, were purchased from Guangzhou Huachuang Plastic Products Co., Ltd., China. The flake PE-MPs were cut from 0.3 mm thick polyethylene sheets, with a particle size ≤ 5 mm, and the polyethylene sheets were purchased from Xindayuan Plastic Materials Co., Ltd. The two forms of powdered and flake PE-MPs simulated common microplastic particles and fragments in the environment, respectively.

[0041] Seeds of taproot and fibrous root crops were selected. For taproot crops, Italian lettuce seeds were purchased from Shouhe Horticulture Company. For fibrous root crops, wheat variety "Baimai 1811" seeds were purchased from local agricultural product retail stores.

[0042] Soil samples were collected (from the Qinyuan Campus of Anhui University, Anhui Province, China, geographical coordinates: 31°82′N, 117°22′E), and pretreated for later use. The pretreatment measures for the crop-growing soil were: air-drying at room temperature, passing through a 5mm sieve, and thoroughly mixing. The initial physicochemical properties of the crop-growing soil were: ammonium nitrogen 4.83 mg / kg, nitrate nitrogen 2.29 mg / kg, pH 7.78, electrical conductivity 194 μS / cm, organic carbon 0.56%, total nitrogen 0.037%, and carbon-nitrogen ratio 15.28.

[0043] S2. Preparation of the microplastic planting environment:

[0044] Powdered PE-MPs (P) and flake PE-MPs (F) were mixed into the treated crop planting soil at gradient concentrations of 0.02%, 0.2%, and 2% (w / w, based on soil dry weight), respectively, to form 6 treatment groups: 0.02% P, 0.2% P, 2% P, 0.02% F, 0.2% F, and 2% F. At the same time, a control group (CK) without added PE-MPs was set up. The crop planting soil of the above 6 treatment groups and 1 control group were prepared in several pots for later use.

[0045] S3. Trial cultivation:

[0046] Take several flowerpots containing soil from several treatment groups and one control group. Sow taproot seeds in half of the pots and fibrous root seeds in the other half. After germination, thin out the seedlings in each pot. Then, cultivate the plants under suitable growing conditions. The specific steps are as follows:

[0047] Sowing and thinning: For lettuce planting, use flower pots with a diameter of 19.7cm and a height of 14cm. Fill each pot with 1.8kg of treated soil and sow 8 seeds per pot. After 30 days, thin the seedlings to 4 plants per pot. For wheat planting, use flower pots with a diameter of 12cm and a height of 17cm. Fill each pot with 1.8kg of treated soil and sow 15 seeds per pot. After 7 days, thin the seedlings to 5 plants per pot.

[0048] Cultivation conditions control: During the cultivation period, the soil moisture content was maintained at 60% of the maximum water holding capacity every 3 days using the weighing method; the cultivation period for lettuce was from December 1, 2024 to February 9, 2025, with the cultivation environment temperature controlled at 25℃, light intensity at 6000 Lux, and a light-dark cycle of 18h / 6h. Ten days after emergence, 100mL of 1 / 2 concentration Hogland's nutrient solution (purchased from Solarbio, model LA2061) was applied to each pot every 3 days; the cultivation period for wheat was from October 9, 2024 to March 7, 2025, with temperature and light fluctuating naturally according to the local season. On December 9, 2024, 0.6g of compound fertilizer was applied to each pot to supplement the nutrients required for wheat growth.

[0049] S4. Index Measurement:

[0050] The growth and physiological indicators of taproot and fibrous root crops in the S3 step trial were measured during the cultivation period.

[0051] The determination of crop growth indicators includes: recording the germination rate, i.e., continuously recording the number of germinated plants after sowing until the data is stable; measuring the plant height and stem diameter regularly; and separating the aboveground part and the root at harvest and measuring the fresh weight of the aboveground part, the dry weight of the aboveground part, the fresh weight of the root, and the dry weight of the root.

[0052] The determination of crop physiological indicators included: leaf chlorophyll content using spectrophotometry; superoxide dismutase (SOD) activity using the nitroblue tetrazolium (NBT) photoreduction method; catalase (CAT) activity using ultraviolet spectrophotometry; malondialdehyde (MDA) content using the thiobarbituric acid (TBA) method; quantitative determination of glutamine synthase (GS) activity using a spectrophotometer; and determination of sucrose synthase decomposition direction (SS-Ⅰ), sucrose synthase synthesis direction (SS-Ⅱ), and sucrose phosphate synthase (SPS) activity using a Greens reagent kit. Soil physicochemical indicators and enzyme activity were determined by measuring pH and conductivity using a pH / conductivity meter; determining nitrate and ammonium nitrogen content using potassium chloride extraction; determining total carbon, total nitrogen, and C / N ratio using an elemental analyzer; and analyzing changes in microbial community composition, diversity, and functional genes using high-throughput sequencing.

[0053] S5. Data Analysis:

[0054] Using the data indicators obtained in step S4, a correlation was constructed between the concentration gradients of different forms of microplastics and the adaptability of plant root types, thereby screening suitable crops for planting in microplastic-polluted areas. The details are as follows:

[0055] 1. Crop germination rate:

[0056] The germination rate data of lettuce and wheat obtained are shown in Table 1. All lettuce in the control group (CK) germinated. All PE-MPs treatment groups had lower germination rates than CK, with 0.02%P and 2%F having the lowest (87.50±10.21%) and 0.02%F the highest (96.88±6.25%). The germination rate of wheat in the control group was 81.50±8.35%. Except for 2%P (75.00±12.33%), which was lower than CK, all other PE-MPs treatment groups had higher germination rates than CK, with 0.02%P having the highest (95.00±10.00%). The effect of microplastics (PE-MPs) on seed germination rate exhibited species specificity, generally inhibiting lettuce germination while generally promoting wheat germination. The effect also varied by morphology; for example, 0.02%F promoted lettuce germination, but 0.02%P inhibited lettuce germination, while 0.02%P promoted wheat germination.

[0057] Table 1. Germination rates of lettuce and wheat

[0058] Processing group CK 0.02%P 0.2%P 2%P 0.02%F 0.2%F 2%F Lettuce germination rate 100±0.00% 87.50±10.21% 93.75±12.50% 93.75±7.22% 96.88±6.25% 93.75±7.22% 87.50±10.21% wheat germination rate 81.50±8.35% 95.00±10.00% 93.25±5.32% 75.00±12.33% 90.00±11.55% 83.25±12.97% 93.25±9.43%

[0059] 2. Plant growth indicators and chlorophyll content:

[0060] (1) The growth trend data of lettuce and wheat obtained are shown in Figure 1 As shown, where, Figure 1 (A) represents the height of the lettuce plant. Figure 1 (B) represents the height of the wheat plant. Figure 1 (C) represents the thickness of the wheat stem.

[0061] from Figure 1We can see that, on day 75, the lettuce plant height was inhibited compared to the control (CK) (7.54±1.01cm), with inhibition rates of 2.19% (0.02%P), 13.32% (0.2%P), 28.34% (2%P), 18.30% (0.02%F), 12.06% (0.2%F), and 24.93% (2%F), respectively, with 2%P and 2%F showing the most significant inhibition. When the wheat culture period reached day 130, the plant height of the control group (CK) wheat was 40.68±2.51cm. The effects of different types of polyethylene microplastics (PE-MPs) on wheat plant height were inconsistent: only the 2% flake PE-MPs treatment group (2%F) showed an inhibitory effect on wheat plant height (1.48%); the remaining treatment groups all showed a promoting effect on wheat plant height (3.74%-6.51%), with 0.02%P and 0.02%F showing similar and minimal inhibition rates, and 0.2%P showing the largest inhibition rate. Regarding wheat stem diameter, the control group (CK) had a stem diameter of 3.70±0.30 mm. All PE-MPs treatment groups increased wheat stem diameter, with increases ranging from 2.91% to 11.71%, with the 0.2% flake PE-MPs treatment group showing the highest increase rate (11.71%) and the 2% flake PE-MPs treatment group showing the lowest increase rate (2.91%).

[0062] (2) The fresh and dry weights of the aboveground parts and roots of lettuce and wheat, as well as the chlorophyll content data, are shown in [reference needed]. Figure 2 As shown, where, Figure 2 (A) is the fresh weight (g) of the above-ground part of the lettuce. Figure 2 (B) is the dry weight (g) of the above-ground part of the lettuce. Figure 1 (C) represents the fresh weight (g) of the lettuce root. Figure 2 (D) is the dry weight (g) of the lettuce root. Figure 2 (E) represents lettuce chlorophyll (mg / g fresh weight). Figure 2 (F) represents the fresh weight (g) of the aboveground parts of wheat. Figure 2 (G) represents the dry weight (g) of the aboveground parts of wheat. Figure 2 (H) represents the fresh weight (g) of wheat roots. Figure 2 (I) represents the dry weight (g) of wheat roots. Figure 2 (J) represents wheat chlorophyll (mg / g fresh weight).

[0063] Figure 2The study presented the fresh and dry weights of the aboveground parts and roots of lettuce and wheat, as well as their chlorophyll content. Compared to the control group (CK), there were no significant differences in the fresh and dry weights and chlorophyll content of the aboveground parts of lettuce. However, the effects of different forms and concentrations of microplastics (PE-MPs) on the fresh and dry weights of the aboveground parts were significant: For powdered microplastics (P), the fresh weight of the aboveground parts of lettuce gradually decreased with increasing concentration (0.02%, 0.2%, 2%), at 43.30±7.89 g, 36.29±7.37 g, and 22.90±2%, respectively. The total amount of microplastics (F) was 6.74g. The 2% P treatment group showed the largest decrease, reducing the amount by 67.82% compared to the control (CK). The 2% F treatment group showed a decrease of 23.44%, second only to the 2% P treatment group in terms of inhibition. In the 0.02% and 0.2% F treatment groups, both the fresh and dry weight of the lettuce aboveground parts increased compared to the control (CK). For example, the 0.02% F treatment group had a leaf fresh weight of 43.30±7.89g and a dry weight of 1.96±0.64g, representing increases of 13.64% and 3.95% respectively compared to the control (CK). The fresh weight of lettuce roots in the microplastic treatment groups (3.71±1.28g-5.36±1.25g) increased compared to the control (CK) (2.97±0.43g), with the same effect observed in the dry weight. The chlorophyll content of lettuce leaves was 0.86±0.11 mg / g in the control group (CK). Except for the 0.02% P treatment group (0.88±0.06 mg / g), which showed an increase, all other treatment groups showed a decrease. The fresh and dry weights of wheat aboveground parts in the CK group were 63.82±3.91 g and 35.55±2.41 g, respectively. The 0.02% F treatment group showed the largest increase in both fresh and dry weights, at 6.40% and 5.08%, respectively. Compared with the CK group (8.76±0.85 g and 1.76±0.45 g), the fresh and dry weights of wheat roots increased in all treatment groups except for the 0.2% F treatment group (8.42±0.63 g), which showed a decrease. The 0.02% F treatment group showed the largest increase, at 37.23% and 44.82%, respectively. Compared with the control (0.62±0.32 mg / g), the chlorophyll content of wheat increased in all treatment groups, with the 0.02% treatment group showing the largest increase at 74.58%.

[0064] 3. Enzyme activity in plant leaves:

[0065] The data on the antioxidant enzyme activity and MDA content of lettuce and wheat are shown in Table 2; the data on the carbon and nitrogen metabolism enzyme activity of lettuce and wheat are shown in Table 3.

[0066] Table 2. Plant antioxidant enzyme activity and MDA content

[0067] Treatments L SOD(U / g FW) L CAT(U / g FW) L MDA ( nmol / g FW) W SOD (U / g FW) W CAT(U / g FW) W MDA ( nmol / g FW) CK 208.43±41.50 36.44±5.43 10.534±1.893 206.36±17.33 132.88±28.81 5.35±2.09 0.02%P 264.94±18.89 34.79±6.64 9.967±1.652 211.83±4.76 111.05±38.66 7.18±1.64 0.2%P 235.21±16.03 32.94±5.04 11.503±1.547 212.28±6.77 143.23±32.97 6.38±2.55 2%P 253.25±11.71 33.53±4.47 10.271±2.891 194.82±18.91 149.46±31.43 8.40±1.12 0.02%F 208.14±63.89 27.30±2.16 14.255±2.803 168.20±23.76 91.63±61.91 4.19±2.21 0.2%F 183.43±23.17 29.97±6.50 13.222±1.571 192.16±16.09 161.78±48.90 6.13±1.52 2%F 243.49±39.41 37.80±7.31 11.194±2.615 192.60±20.34 117.29±33.82 4.84±0.90

[0068] Note: "L" represents lettuce, and "W" represents wheat.

[0069] Table 3. Data on Crop Carbon and Nitrogen Metabolism Enzyme Activities

[0070] Treatments LGSA540 / (g·h) L SS-Ⅰ(㎍ / min / g FW) L SS-Ⅱ (㎍ / min / g FW) L SPS (㎍ / min / g FW) WGSA540 / (g·h) W SS-Ⅰ(㎍ / min / g FW) W SS-Ⅱ(㎍ / min / g FW) W SPS (㎍ / min / g FW) CK 0.43±0.11 1238.04±93.53 373.94±118.36 419.46±283.13 1.75±0.47 1155.22±81.78 1066.63±284.12 379.95±150.95 0.02%P 0.45±0.06 1284.72±198.50 476.89±185.54 188.21±53.51 1.11±0.61 1239.99±102.61 1169.46±397.73 339.51±202.62 0.2%P 0.31±0.04 1276.38±171.28 535.73±87.26 448.00±372.03 1.19±0.32 1250.67±161.07 1660.50±652.84 222.76±93.55 2%P 0.31±0.07 1338.56±74.12 542.69±177.38 471.46±277.90 2.10±0.87 1407.44±62.74 1147.65±176.75 278.66±147.60 0.02%F 0.31±0.02 1324.50±108.11 521.23±42.79 557.20±257.13 1.40±0.49 1384.72±354.33 1160.15±494.74 499.41±207.13 0.2%F 0.43±0.13 1319.16±204.40 319.22±72.52 376.53±217.43 2.72±0.40 1420.85±277.47 1041.16±82.68 368.99±117.25 2%F 0.40±0.08 1501.45±99.66 540.57±142.49 524.53±77.06 1.96±0.65 1397.74±220.90 1171.70±343.12 455.31±176.38

[0071] Note: "L" represents lettuce, and "W" represents wheat.

[0072] As shown in Table 2, the effects of microplastics on plant antioxidant indices varied by morphology, concentration, and crop. In lettuce, SOD activity was increased by all powdered microplastics compared to the control (CK), with the largest increase (27.11%) observed in the 0.02% P treatment group. SOD activity decreased by 12.00% in the 0.2% F treatment group. However, CAT activity was lower than CK in all treatments except the 2% F group (37.80±7.31 U / g FW), which was slightly higher than CK (36.44±5.43 U / g FW) (the lowest being the 0.02% F group at 27.30±2.16 U / g FW). MDA content was higher in the 0.02% F and 0.2% F treatment groups than in CK, and lower in the 0.02% P and 2% P treatment groups than in CK. In wheat, SOD activity was higher than CK in the 0.02% P and 0.2% P treatment groups, but lower in all other treatments, with the 0.02% F treatment group showing the lowest activity. The 0.02% F treatment group also had the lowest CAT activity. The 0.02%P treatment group had the highest MDA content compared to the CK group, while the 0.02%F treatment group had the lowest MDA content.

[0073] As shown in Table 3, the activities of key enzymes in carbon and nitrogen metabolism differed between lettuce and wheat under different concentrations of microplastics (powdered P and flake F). For wheat, the 2% F treatment group showed a comprehensive positive response, with higher activities of glutamine synthase (GS) and sucrose phosphate synthase (SPS) in its leaves compared to the control. Simultaneously, the activities of sucrose synthase (SS) in both directions were also enhanced, indicating more active carbon and nitrogen metabolism in wheat under this treatment, thus it can be considered a suitable treatment for cultivation. In contrast, lettuce showed metabolic imbalances in response to all treatments. Among all treatments, no group consistently showed a sustained increase in the activities of both GS (a key enzyme in nitrogen metabolism) and SPS (a key enzyme in carbon metabolism); at least one carbon and nitrogen metabolic pathway was inhibited, indicating that lettuce is more sensitive to microplastic stress.

[0074] 4. Crop rhizosphere soil:

[0075] The obtained data on pH, electrical conductivity (EC), state organic carbon (SOC), and C / N ratio of the rhizosphere soil for lettuce and wheat are shown in the figure. Figure 3 As shown. Among them, Figure 3 (A) Figure 3 (B) is a graph showing pH data. Figure 3 (C) Figure 3 (D) is a graph showing electrical conductivity (EC) data. Figure 3 (E) Figure 3(F) is a graph of organic carbon (SOC) data. Figure 3 (G) Figure 3 (H) is a C / N data graph.

[0076] The obtained data on nitrate nitrogen, ammonium nitrogen, and nitrogen content in the rhizosphere soil of lettuce and wheat are shown in the figure. Figure 4 As shown. Among them, Figure 4 (A) Figure 4 (D) is a graph showing nitrate nitrogen data. Figure 4 (B) Figure 4 (E) is a graph showing ammonium nitrogen data. Figure 4 (C) Figure 4 (F) is a graph showing nitrogen content data.

[0077] The data on sucrase (SUC), dehydrogenase (DH), urease (URE), and catalase (CAT) activities in the rhizosphere soil of lettuce and wheat are shown in the figure. Figure 5 As shown. Among them, Figure 5 (A) is a graph showing the activity data of lettuce sucrase (SUC). Figure 5 (B) is a graph showing wheat sucrase (SUC) activity data. Figure 5 (C) is a graph showing the activity data of lettuce dehydrogenase (DH). Figure 5 (D) is a graph showing wheat dehydrogenase (DH) activity data. Figure 5 (E) is a graph showing the urease (URE) activity data of lettuce. Figure 5 (F) is a graph showing wheat urease (URE) activity data. Figure 5 (G) is a graph showing the activity data of catalase (CAT) in lettuce. Figure 5 (H) is a graph showing wheat catalase (CAT) activity data.

[0078] like Figure 3 As shown, microplastic treatment had no significant effect on the pH of the rhizosphere soil of lettuce and wheat (p > 0.05). Figure 3 (A, 3B). Regarding electrical conductivity, microplastic treatment had no significant overall effect on the rhizosphere soil of lettuce, but powdered microplastic treatment reduced it by approximately 7.95%, 4.71%, and 3.04%, respectively (p > 0.05). Figure 3 C); In contrast, low-concentration flake microplastic treatment (0.02%F) significantly reduced the rhizosphere soil electrical conductivity of wheat by 13.38% (p < 0.05, Figure 3 D). Regarding carbon-related indicators, high-concentration powdered microplastic treatment (2% P) significantly increased the organic carbon content of the rhizosphere soil of lettuce ( Figure 3 E), the carbon-to-nitrogen ratio also showed the same trend (p < 0.05, Figure 3G). The organic carbon content and carbon-nitrogen ratio in the wheat rhizosphere soil increased by 88.28% and 154.36%, respectively, but the differences were not significant (p > 0.05). Figure 3 F, 3H).

[0079] like Figure 4 As shown, regarding nitrogen, the nitrate nitrogen content in the rhizosphere soil of lettuce significantly increased under the 2% F treatment (p < 0.05). Figure 4 A), while ammonium nitrogen and nitrogen showed no significant changes ( Figure 4 B, 4C). No significant differences were observed in the nitrate nitrogen, ammonium nitrogen, and nitrogen content of the wheat rhizosphere soil. Figure 4 (D, 4E, 4F), but compared with the control group, microplastic treatments led to a decrease in nitrogen content in both crops.

[0080] like Figure 5 As shown, microplastic treatment had no significant effect on the activities of sucrase (SUC) and dehydrogenase (DH) in the rhizosphere soil of both crops (p > 0.05). Figure 5 A-5D). Regarding urease (URE), the rhizosphere soil of lettuce showed no significant response to microplastic treatment. Figure 5 E), while wheat rhizosphere soil significantly increased under 0.2% F and 2% F treatments (p < 0.05, Figure 5 F). In contrast, catalase (CAT) activity showed a different pattern: lettuce rhizosphere soil was significantly increased under 0.2% F and 2% F treatments (p < 0.05, Figure 5 G), but the rhizosphere soil of wheat was not significantly affected (p > 0.05). Figure 5 H). Overall, microplastic stress showed differential effects on the activity of extracellular enzymes in the rhizosphere soil of the two crops.

[0081] 5. Crop soil microbial community:

[0082] The obtained OTU composition and bacterial community diversity diagram of lettuce rhizosphere soil bacteria and fungi are shown in [link to diagram]. Figure 6 As shown. Among them, Figure 6 (A) is a diagram showing the OTU composition of each bacterial community. Figure 6 (B) is a diagram showing the OTU composition of each fungal community. Figure 6 (C) is a graph showing the relative abundance data at the bacterial phylum level. Figure 6 (D) is a graph showing bacterial taxa with significant differences in relative abundance at the phylum level compared to the control group. Figure 6 (E) is a graph showing the relative abundance of bacteria at the genus level. Figure 6 (F) is a graph showing bacterial genera with significant differences in mean relative abundance among groups.

[0083] The obtained diagram of the diversity changes in the rhizosphere soil fungal community of lettuce is shown in [reference needed]. Figure 7 As shown. Figure 7 (A) is a graph showing the relative abundance of fungi at the phylum level. Figure 7 (B, D) are plots showing fungal taxa data where the relative abundance at the phylum level differed significantly from the control group. Figure 7 (C) is a graph showing the relative abundance of fungi at the genus level. Figure 7 (E) is a graph showing the fungal taxa data where the relative abundance at the genus level differs significantly from that of the control group.

[0084] The obtained OTU composition and bacterial community heatmap of wheat rhizosphere soil bacteria are shown in [reference needed]. Figure 8 As shown. Among them, Figure 8 (A) is a graph showing the composition of bacterial community OTUs. Figure 8 (B) is a heatmap of the bacterial community in the rhizosphere soil of wheat.

[0085] The obtained diagrams of OTU composition and fungal community diversity changes in wheat rhizosphere soil are shown in [reference needed]. Figure 9 As shown. Among them, Figure 9 (A) is a graph showing the composition of fungal community OTUs. Figure 9 (B) is a graph showing the relative abundance of fungi at the phylum level. Figure 9 (C) is a graph showing the relative abundance of fungi at the genus level. Figure 9 (D) is a graph showing the differences between fungal genera.

[0086] like Figure 6 , Figure 7 As shown, 8564 OTUs (97% similarity) were obtained from the bacterial community co-clustering of lettuce rhizosphere soil samples, of which 2673 were shared by the seven treatment groups. The number of unique OTUs in each treatment group were as follows: CK 248, 0.02%P 386, 0.02%F 396, 0.2%P 281, 0.2%F 278, 2%P 279, and 2%F 318. Low concentration of flake microplastics (0.02%F) had the strongest disturbance to the bacterial community, with the highest proportion of unique OTUs (4.51%), which may be related to the enrichment of degrading functional bacteria; while the effect of the same concentration of powdered microplastics (0.02%P) was weaker (2.90%). The 0.2% P treatment group showed higher community stability (unique OTU percentage of 1.82%), while the high concentration treatments (2% P and 2% F) showed more similar community responses (3.25%–3.26%). Figure 6 A). At the phylum level, Proteobacteria, Cyanobacteriota, Actinobacteriota, Acidobacteriota, and Bacteroidota were the dominant taxa, with relative abundances of 78.04%–82.12% (A). Figure 6C). Compared with the CK (2.33%), the relative abundance of Patescibacteria was significantly increased in the 2%P treatment group (3.04%) (p<0.05). Figure 6 D). At the genus level, *norank_o__Chloroplast*, *Arthrobacter*, *Massilia*, and *Oxalicibacterium* are dominant genera. Figure 6 E). Significant differences in the relative abundance of Arthrobacter and Methylotenera were observed among the treatment groups (p<0.05). Figure 6 F).

[0087] A total of 1728 OTUs were obtained from the co-clustering of lettuce rhizosphere soil fungal communities, of which 215 (12.44%) were core communities shared by all groups. The control group (CK) had 115 unique OTUs (6.65%), while the number of unique OTUs was significantly reduced in the 0.02%P (67, 3.88%) and 2%F (59, 3.41%) treatments. Figure 6 B). At the phylum level, Ascomycota, Olpidiomucota, Mortierellomycota, and Chytridiomycota are the dominant groups. Figure 7 A). Compared with the CK group, there were significant differences in the relative abundance of the two phyla in the 2%F treatment group: the relative abundance of Ascomycota decreased significantly (from 80.7% to 20.75%), while the relative abundance of Olpidiomycota increased significantly (from 0.51% to 63.26%), and both differences were statistically significant (p<0.05). Figure 7 B, 7D). At the genus level, microplastic treatment led to an increase in the relative abundance of Olpidiaster compared to CK (0.51%). Figure 7 C), and significantly increased to 63.26% in the 2%F (63.26%) treatment, significantly increased (p<0.05, Figure 7 E).

[0088] like Figure 8 , Figure 9 As shown, the number of bacterial sequences in each sample of wheat rhizosphere soil ranged from 45,184 to 66,900, with 97% of the sequences clustering at the same threshold, resulting in the identification of 4,235 OTUs. The Venn diagram generated from the OTUs showed that the CK group shared most of the OTUs with the six MPs treatment groups. However, we observed that, except for the 2%F treatment group which had more unique OTUs (116) than the CK group (108), the other treatment groups had fewer unique OTUs than the CK group. Figure 8A). The heatmap shows the relative abundance of bacterial communities at the genus level under different treatment groups, and the phylum to which the bacteria belong is labeled. The figure shows that *Arthrobacter*, *TM7a*, *Sphingomonas*, and *Massilia* are the dominant genera, belonging to the phyla *Actinomycetota*, *Patescibacteria*, and *Pseudomonadota*, respectively. Figure 8 B).

[0089] The system systematically demonstrates the changes and significant differences in the genus-level composition of wheat rhizosphere soil fungal communities under different microplastic treatments. Petal-shaped Venn diagrams reveal the differentiation in fungal community structure among different treatment groups: coexisting OTUs accounted for only 14.68% of the total across the seven treatment groups, while each group possessed a varying number of unique OTUs (22-74), with the 2%P treatment group having the highest number of unique genera. Figure 9 A). Mortierellomycota and Ascomycota were the dominant phyla, with relative abundances of 65.27%-41.22% and 55.35%-30.48%, respectively. Figure 9 B). At the genus level, Mortierella (58.82%-41.15%) and Fusarium (41.83%-19.38%) are the dominant genera. Figure 9 C), and the relative abundance of Fusarium showed significant differences between groups (p<0.05); Figure 9 D).

[0090] 6. Crop rhizosphere soil carbon and nitrogen metabolism:

[0091] The obtained β-diversity map of carbon and nitrogen metabolism functions in the rhizosphere soil microbial community of lettuce is shown in [reference needed]. Figure 10 As shown. Among them, Figure 10 (A) is a graph showing the differences in β-diversity among groups of functional genes related to carbon metabolism. Figure 10 (B) is a graph showing the differences in β diversity among groups of nitrogen metabolism-related functional genes.

[0092] The obtained functional gene analysis diagram related to carbon and nitrogen metabolism in lettuce rhizosphere soil is shown in [link to diagram]. Figure 11 As shown. Among them, Figure 11 (A) is a graph showing the relative abundance of each function of the carbon metabolism gene set at the functional level. Figure 11 (B) is a bar chart showing the LEfSe differential discrimination analysis of the functional carbon metabolism gene set. Figure 11 (C) is a bar chart of LEfSe differential discrimination analysis of nitrogen metabolism gene sets at the gene level.

[0093] The differential gene maps obtained between the experimental group and the control group are shown in [the image]. Figure 12 As shown. Among them, Figure 12(A) is a differential gene diagram obtained by comparing the CK and 2%P groups. Figure 12 (B) is a differential gene diagram obtained by comparing the CK and 2%F groups.

[0094] like Figure 10 As shown, among the 1,299,241 total genes present in the rhizosphere soil of lettuce, 47,224 and 5,999 non-redundant genes involved in carbon and nitrogen transformation reactions were identified, respectively. In carbon metabolism, the distance values ​​between the 0.02%P and 2%P groups were relatively high; between groups, the differences between CK and 0.2%P and between 0.02%F and 2%F were extremely significant (p<0.01), and there were also significant differences between the powdered MPs treatment groups between 0.02%P and 0.2%P, and between 0.2%P and 2%P (p<0.05). In nitrogen metabolism, the 0.2%P group had the lowest distance value, while the CK, 0.02%P, and 2%P groups had higher distance values. In the inter-group comparison, the differences between CK and 0.2%P and 0.02%F were extremely significant (p<0.01), and the differences between 0.02%P and 0.2%P and between 0.2%P and 2%P in the powder MPs treatment group were extremely significant (p<0.01), reflecting the selective perturbation of the β diversity of nitrogen metabolism functional genes in microbial communities by microplastics.

[0095] like Figure 11 , Figure 12 As shown, the functional relative abundance analysis shows ( Figure 11 A), hemicellulose, starch, dicarboxylate-hydroxybutyrate cycle, and amino acid utilization all showed high relative abundance in all treatment groups. LEfSe analysis revealed that cellulose and aerobic oxidation of methane were the differentially expressed functions among the groups (p<0.05). Figure 11 B).

[0096] Forty target genes related to nitrogen metabolism were screened, and LEfSe analysis showed that ( Figure 11 C), differential enrichment of nitrogen-related functional genes was observed among the groups (LDA>3, P<0.05). The 2%P group was enriched with genes related to nitrate reduction (narH, narY, nxrB), hydroxylamine oxidation (hao), and ammonia oxidation (pmoC-amoC); the CK group was enriched with the glutamate synthesis-related gene gltD; and the 0.2%F group was enriched with the nitrogen fixation-related genes nifD / nifK. Through comparison between the two groups ( Figure 12A, 12B), the high concentration treatment groups (2%P and 2%F) compared with CK, both significantly reduced the abundance of gltD and significantly increased the abundance of hao (p<0.05). 2%P also significantly increased the abundance of narH, narY and nxrB.

[0097] The obtained intergenomic β-diversity map of carbon and nitrogen metabolism function in wheat rhizosphere soil microbial community is shown in [reference needed]. Figure 13 As shown. Among them, Figure 13 (A) is a graph showing the intergroup differences in β-diversity of functional genes related to carbon metabolism in wheat rhizosphere soil. Figure 13 (B) is a graph showing the differences in β-diversity among functional genes related to nitrogen metabolism in wheat rhizosphere soil.

[0098] The obtained functional gene analysis diagram related to carbon and nitrogen metabolism in wheat rhizosphere soil is shown in [link to diagram]. Figure 14 As shown. Among them, Figure 14 (A) is a graph showing the relative abundance of each function of the carbon metabolism gene set at the functional level. Figure 14 (B) Comparative bar chart of multiple groups of functional genes related to nitrogen metabolism at the functional level

[0099] like Figures 13-14 As shown, among the 1,974,814 total genes detected in wheat rhizosphere soil, 70,168 and 8,128 non-redundant genes involved in carbon and nitrogen transformation reactions were identified, respectively. In the β-diversity analysis of the abundance of functional genes related to carbon metabolism, (…) Figure 13 A) Compared with CK, except for the 2%F treatment group, the functional gene community structure of all other groups showed significant differences (p<0.05), with 0.02%F and 0.2%F showing highly significant differences (p<0.01). In nitrogen metabolism ( Figure 13 B), compared with CK, except for the 2%F treatment group, the functional gene community structure of the other groups was significantly different (p<0.05), and 0.02%P, 0.2%P and 0.2%F were extremely significant (p<0.01).

[0100] Depend on Figure 14 (A) It can be seen that Hemicellulose, the Reductive citrate cycle (Arnon-Buchanan cycle), and Starch are dominant functions. MPs treatment did not significantly affect key processes in the wheat rhizosphere nitrogen metabolism pathway (p>0.05). Figure 14 B).

[0101] 7. Crop rhizosphere soil-crop-microbe system:

[0102] Based on the partial least squares path model (PLS-PM) analysis results (lettuce: GoF = 0.46; wheat: GoF = 0.49), microplastics (MPs) exhibit complex multipath influence mechanisms in the soil-microbe-plant system.

[0103] The partial least squares path modeling analysis diagrams obtained from the lettuce and wheat systems regarding microplastic concentration speciation, soil nutrients (organic carbon, C / N), microorganisms (Bacterial_chao, fungal_ace), soil enzyme activities (NAG, SUC, DH), plant physiology (SPS, C / N, ammonium nitrogen), and plant growth (plant height, leaf dry weight) are shown in [link to diagram]. Figure 15 As shown. Among them, Figure 15 (A) is a diagram of the lettuce system. Figure 15 (B) is a wheat system diagram; Figure 15 The red and blue arrows represent positive and negative relationships, respectively. The number next to the arrow is the path coefficient (β). The line thickness indicates the degree of significance. Dashed lines represent paths with no significant difference. Asterisks indicate statistically significant differences (*P < 0.05, **P < 0.01, ***P < 0.001).

[0104] The direct and indirect effects among the latent variables in the lettuce system are shown in Table 4; the direct and indirect effects among the latent variables in the wheat system are shown in Table 5.

[0105] Table 4. Direct and indirect effects among latent variables in the lettuce system

[0106] Path Relationship direct effects Indirect effects Total effect Microplastics -> Soil Nutrients 0.6019 0.0000 0.6019 Microplastics -> Microbial biodiversity 0.6492 -0.2916 0.3577 Microplastics -> Soil Enzyme Activity 0.7276 -0.0818 0.6457 Microplastics -> Plant Physiology -0.1444 0.4688 0.3245 Microplastics -> Lettuce growth -0.6840 0.0004 -0.6836 Soil nutrients -> Microbial diversity -0.4845 0.0000 -0.4845 Soil nutrients -> Soil enzyme activity -0.2268 -0.0741 -0.3009 Soil nutrition -> Plant physiology 0.0754 -0.2513 -0.1759 Soil nutrients -> Lettuce growth -0.0633 -0.0351 -0.0984 Microbial diversity -> Soil enzyme activity 0.1529 0.0000 0.1529 Microbial diversity -> Plant physiology 0.1699 0.0859 0.2558 Microbial diversity -> Lettuce growth 0.0640 -0.0193 0.0447 Soil enzyme activity -> Plant physiology 0.5616 0.0000 0.5616 Soil enzyme activity -> lettuce growth 0.0887 -0.0721 0.0166 Plant Physiology -> Lettuce Growth -0.1284 0.0000 -0.1284

[0107] Table 5. Direct and indirect effects among latent variables in the wheat system

[0108] Path Relationship direct effects Indirect effects Total effect Microplastics -> Soil Nutrients -0.7067 0.0000 -0.7067 Microplastics -> Microbial biodiversity -0.2824 0.0843 -0.1981 Microplastics -> Soil Enzyme Activity 0.2367 0.0945 0.3313 Microplastics -> Plant Physiology 0.1999 0.0343 0.2342 Microplastics -> Wheat Growth 0.8178 -0.5936 0.2242 Soil nutrients -> Microbial diversity -0.1193 0.0000 -0.1193 Soil nutrients -> Soil enzyme activity 0.0156 0.0635 0.0791 Soil nutrition -> Plant physiology -0.2772 -0.0530 -0.3302 Soil nutrients -> Wheat growth 0.7587 0.0868 0.8455 Microbial diversity -> Soil enzyme activity -0.5325 0.0000 -0.5325 Microbial diversity -> Plant physiology 0.2000 0.1960 0.3960 Microbial diversity -> Wheat growth 0.5099 -0.3446 0.1653 Soil enzyme activity -> Plant physiology -0.3681 0.0000 -0.3681 Soil enzyme activity -> wheat growth 0.3829 0.1308 0.5137 Plant Physiology -> Wheat Growth -0.3553 0.0000 -0.3553

[0109] like Figure 15As shown in (A) and Table 4, microplastics exhibited a significant direct negative effect on lettuce growth (β = -0.68, p < 0.05), with weak indirect effects. Microplastics significantly promoted soil nutrients (β = 0.60, p < 0.001), soil enzyme activity (β = 0.73, p < 0.01), and microbial diversity (β = 0.65, p < 0.01). Within the system's pathways, soil nutrients significantly inhibited microbial diversity (β = -0.48, p < 0.05), while soil enzyme activity significantly promoted plant physiological indicators (β = 0.56, p < 0.05). Notably, while the direct effect of microplastics on plant physiology was negative (β = -0.14), the strong positive indirect effect (β = 0.47) through pathways such as soil enzyme activity turned its total effect positive (β = 0.32).

[0110] In the wheat system ( Figure 15 B (Table 5) shows that microplastics significantly promoted wheat growth directly (β = 0.82, p < 0.001), but a strong indirect inhibitory effect (β = -0.56) weakened this promoting effect, resulting in a total effect reduced to 0.22. Microplastics significantly inhibited soil nutrients (β = -0.71, p < 0.001), while soil nutrients significantly promoted wheat growth (β = 0.76, p < 0.001). Microplastics had no significant direct effect on microbial diversity (β = -0.28, p > 0.05), but microbial diversity significantly promoted wheat growth directly (β = 0.51, p < 0.01). In addition, soil enzyme activity and plant physiology significantly promoted (β = 0.38, p < 0.05) and inhibited (β = -0.36, p < 0.05) wheat growth, respectively.

[0111] Therefore, the partial least squares path model (PLS-PM) reveals fundamental differences in the mechanisms by which microplastics affect lettuce and wheat, highlighting the complexity of their role in the soil-plant-microbe system. In the lettuce system, while microplastics (MPs) directly inhibit growth, they generate a stronger positive indirect effect through a key pathway of strongly promoting soil enzyme activity, ultimately turning the overall physiological effect on plants from negative to positive. In other words, changes in soil enzyme activity caused by MPs directly and significantly affect plant growth. Conversely, in the wheat system, the direct promoting effect of MPs is significantly weakened by their strong indirect negative effect through inhibiting soil nutrients. This starkly different mechanism indicates that the ecological effects of MPs are highly dependent on plant species: shallow-rooted crops like lettuce may be more susceptible to changes in soil microbial activity driven by MPs, while nutrient-demanding crops like wheat are more sensitive to the soil fertility depletion they induce.

[0112] As can be seen from Example 1:

[0113] 1. Under low concentrations of PE-MPs (≤0.02% w / w), taproot crops are more sensitive, while fibrous-root crops are tolerant and benefit. The correlation mechanism between root type and the concentration of different forms of PE-MPs is as follows: at low concentrations, the "carrier effect" (adsorption of mineral elements) of flaky PE-MPs is beneficial to the absorption of fibrous roots, while taproots, due to their large taproots and sparse lateral roots, only benefit when flaky PE-MPs are evenly dispersed. Powdered PE-MPs tend to agglomerate and block root hairs.

[0114] 2. Under medium concentrations of PE-MPs (0.2% w / w), taproot systems were suppressed, while fibrous root systems compensated by increased activity. The relationship between root type and PE-MPs concentration is as follows: at medium concentrations, the fibrous root system maintains its growth through "dispersion buffering" (fine fibrous roots disperse MPs stress) and microbial interactions, while the taproot system, dominated by the main root, experiences metabolic inhibition due to excessively high local MPs concentrations.

[0115] 3. Under high concentrations of PE-MPs (2% w / w), the taproot system was severely damaged, while the fibrous root system showed resistance. The correlation mechanism between root type and PE-MPs concentration is as follows: at high concentrations, the "structural resistance" (fine fibrous roots, high resistance to MPs penetration) and functional gene adaptation (such as activation of the nitrate reduction pathway) of the fibrous root system make it tolerant, while the taproot system, due to its large taproot and weak repair capacity, is susceptible to physical damage from MPs and microbial dysbiosis.

[0116] As demonstrated in Example 1, the crop screening method for microplastic-polluted areas based on root type and morphological concentration of this invention clarifies the crop selection for different forms of PE-MPs at different concentrations, demonstrating strong targeting. The method uses a dual-dimensional approach, measuring crop growth and physiological indicators, to determine crop suitability with high accuracy. The standardized process (fixed concentration gradient, culture conditions, and measurement methods) allows for direct reuse. In field applications, only key indicators (such as plant height, root dry weight, and GS activity) need to be measured for rapid determination, resulting in good application effects and strong operability.

[0117] The above is an exemplary description of the invention. Obviously, the specific implementation of the invention is not limited to the above-described manner. Any non-substantial improvement made using the inventive concept and technical solution of the invention, or the direct application of the inventive concept and technical solution to other situations without modification, is within the protection scope of the invention.

Claims

1. A method for screening crops in microplastic-polluted areas based on root type and speciation concentration, characterized in that, Includes the following steps: S1. Material Preparation: Polyethylene microplastics (PE-MPs) were prepared, including powdered PE-MPs and flake PE-MPs. Seeds of taproot and fibrous root crops were selected, and crop planting soil was collected and pretreated for later use. S2. Preparation of the microplastic planting environment: Powdered PE-MPs and flake PE-MPs were mixed into the treated crop planting soil at multiple gradient concentrations to form several treatment groups; at the same time, a control group CK was set up with crop planting soil without added PE-MPs; the crop planting soil of the above treatment groups and 1 control group were placed in several pots for later use. S3. Trial cultivation: Take several flowerpots containing soil for several treatment groups and one control group of crops. Sow taproot seeds in half of the pots and fibrous root seeds in the other half. After germination, thin out the seedlings in each pot. Then, cultivate the plants under suitable growing conditions. S4. Index Measurement: The growth and physiological indicators of taproot and fibrous root crops in the S3 step trial were measured during the cultivation period. S5. Data Analysis: By using the data indicators obtained in step S4, we can construct a correlation between the concentration gradients of different forms of microplastics and the adaptability of plant root types, thereby screening out suitable crops for planting in microplastic-polluted areas.

2. The crop screening method for microplastic-polluted areas based on root type and speciation concentration according to claim 1, characterized in that, In step S1, the particle size of the powdered PE-MPs is 120μm to 180μm; the sheet-like PE-MPs are cut from polyethylene sheets with a thickness of 0.3mm and have a particle size ≤5mm.

3. The crop screening method for microplastic-polluted areas based on root type and speciation concentration according to claim 1, characterized in that, In step S1, the taproot crop seeds are lettuce seeds; the fibrous root crop seeds are wheat seeds.

4. The crop screening method for microplastic-polluted areas based on root type and speciation concentration according to claim 1, characterized in that, In step S1, the pretreatment measures for the crop planting soil are as follows: after being air-dried at room temperature, it is passed through a 5mm sieve and thoroughly mixed; the initial physicochemical properties of the crop planting soil are: ammonium nitrogen 4.83mg / kg, nitrate nitrogen 2.29mg / kg, pH 7.78, electrical conductivity 194μS / cm, organic carbon 0.56%, total nitrogen 0.037%, and carbon-nitrogen ratio 15.

28.

5. The crop screening method for microplastic-polluted areas based on root type and speciation concentration according to claim 1, characterized in that, In step S2, multiple gradient concentrations are specified as follows: powdered PE-MPs or flake PE-MPs are 0.02%, 0.2%, and 2% of the dry weight of the soil, respectively.

6. The crop screening method for microplastic-polluted areas based on root type and speciation concentration according to claim 1, characterized in that, In step S4, the determination of crop growth indicators includes: recording the germination rate, i.e., continuously recording the number of germinations after sowing until the data is stable; measuring the crop height and stem diameter at regular intervals; and separating the aboveground part and the root at harvest time, and measuring the fresh weight of the aboveground part, the dry weight of the aboveground part, the fresh weight of the root, and the dry weight of the root respectively.

7. The crop screening method for microplastic-polluted areas based on root type and speciation concentration according to claim 1, characterized in that, In step S4, the determination of crop physiological indicators includes: determining leaf chlorophyll content using spectrophotometry; determining superoxide dismutase activity using the nitroblue tetrazolium photoreduction method; determining catalase activity using ultraviolet spectrophotometry; determining malondialdehyde content using the thiobarbituric acid method; quantitatively determining glutamine synthase activity using a spectrophotometer; determining the direction of sucrose synthase decomposition, the direction of sucrose synthase synthesis, and the activity of sucrose phosphate synthase using a Green's reagent kit; determining soil physicochemical indicators and enzyme activity, including pH and conductivity using a pH / conductivity meter; determining nitrate nitrogen and ammonium nitrogen content using potassium chloride extraction; determining total carbon, total nitrogen, and C / N ratio using an elemental analyzer; and analyzing changes in microbial community composition, diversity, and functional genes using high-throughput sequencing.

Images