Application of Mn3O4 nanofertilizer in alleviating the inhibitory effect of microplastic particles on plant growth

Abstract

The present invention discloses the application of Mn3O4 nanofertilizer in alleviating the inhibition of plant growth by microplastic particles. The present invention finds that Mn3O4 can alleviate the stress of PS on the root length and fresh weight of Arabidopsis thaliana, and promote the growth of Arabidopsis thaliana. In addition, when Fv / Fm is 0.7, Arabidopsis thaliana is considered to be stress-free. The present invention finds that PS exerts stress on Arabidopsis thaliana, and Mn3O4 has the ability to alleviate PS stress. According to the chlorophyll fluorescence-related parameters provided by the present invention, it is proved that Mn3O4 alleviates the photosynthesis of Arabidopsis thaliana under PS stress, and 100-200μg / mL of Mn3O4 has the best effect on alleviating PS stress. Therefore, the Mn3O4 nanofertilizer provided by the present invention has a mitigating effect on the root length and photosynthesis of Arabidopsis thaliana under PS stress, thereby significantly promoting the growth and development of plants.

Description

Technical Field

[0001] The invention relates to the application of Mn3O4 nano fertilizer in alleviating the inhibition of microplastic particles on plant growth, and belongs to the technical field of plant physiology. Background Art

[0002] Plastic products are widely used in production and daily life due to their low cost, strong ductility, and stable properties. Since the large-scale production of plastics in the 20th century, plastic production has increased annually, currently exceeding 3,200 million tons globally annually. However, while providing convenience to human life, plastics also pose serious environmental risks due to their low recycling rates and difficulty in decomposing. Microplastics, as an emerging pollutant, have attracted significant attention both domestically and internationally.

[0003] The concept of microplastics, first coined by Thompson in Science in 2004, refers to plastic fragments and particles smaller than 5 mm in diameter. Microplastics are difficult to degrade, carry a high concentration of pollutants, and can be ingested by plants and animals, posing a serious threat to the ecological environment and human health. At the Second United Nations Environment Assembly in 2016, microplastic pollution was listed as the second-most important scientific issue in environmental and ecological science research, recognized as a major global environmental problem alongside global climate change, ozone depletion, and ocean acidification.

[0004] Polystyrene (PS) is one of the world's top five most widely used plastics. Due to its excellent insulating properties, transparency, and weather resistance, it is widely used in common rigid plastic items such as packaging, construction materials, household goods, appliances, medical devices, and electronics. According to a 2023 report released by the United Nations Environment Programme, global plastic production exceeds 430 million tons annually, two-thirds of which are short-lived products that quickly become waste. Global per capita plastic consumption is projected to increase from 46.60 kg in 2020 to 84.37 kg in 2035. Furthermore, according to the Organization for Economic Cooperation and Development, approximately 350 million tons of plastic waste was generated globally in 2019, of which 45% was landfilled, 22% was discarded on land or at sea, 17% was incinerated, and only 9% was reused. Although PS is manufactured to perform certain functions, its high-temperature resistance and complex chemical structure make it extremely difficult to degrade in the environment. During the long degradation process of PS, smaller PS particles such as micron- and nano-sized particles are produced. Plastic pollution has become a recognized global environmental problem.

[0005] Oceans, rivers, and land are considered significant reservoirs for PS. Various human activities and industrial processes generate large quantities of PS-containing wastewater and sludge discharged into these areas, further contaminating agricultural soils through air deposition, surface runoff, sludge utilization, and residual agricultural film. Plants and crops in the soil are forced to absorb PS from the environment and transfer it to their stems, where it accumulates in leaves or roots. This severely impacts plant germination and growth, posing varying degrees of potential threats to organisms at different levels of the ecosystem. When PS accumulates to a certain level within plants and crops, it can severely inhibit their growth. Furthermore, in addition to disrupting normal growth, PS stress on plants and crops manifests itself in physiological processes such as reduced photosynthesis efficiency and respiration, causing significant harm to agriculture and other fields. However, existing methods and applications for mitigating PS stress rarely address methods for alleviating PS stress on plants and crops. Therefore, the search for environmentally friendly methods that can mitigate PS stress on plant and crop growth and photosynthesis is of great significance. Summary of the Invention

[0006] To address the current problem of microplastics causing stress on plants and crops, which in turn affects their normal growth, the present invention provides a method for using Mn3O4 nanofertilizer to alleviate the growth inhibition of microplastic particles on plants. Specifically, the present invention adopts the following technical solutions:

[0007] In the present invention, Mn3O4 nanofertilizer is used to alleviate the inhibitory effect of microplastic particles on plant growth. The Mn3O4 nanofertilizer is an organic and / or inorganic fertilizer containing at least Mn3O4 nanoparticles. The microplastics include at least one of polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyamide, and their derivatives. In this way, the present invention can use Mn3O4 alone as a nanofertilizer to alleviate the stress of PS on plant roots and photosynthesis, or it can be used with the addition of some additives.

[0008] Among them, preferably, the size of the Mn3O4 nanoparticles is 5-50 nm, preferably 8-20 nm, and more preferably 10-15 nm.

[0009] Preferably, the microplastic is at least one of polystyrene and its derivatives, more preferably, the polystyrene and its derivatives include at least one of amino-functionalized polystyrene, sulfonic acid polystyrene, and carboxylated polystyrene. It is well known that plastics are subject to certain weathering and degradation in the environment, which not only changes the physical and chemical properties of microplastics, but also changes their surface charge. Whether microplastics cause stress to plants, whether they accumulate on the surface of plants or are internalized into plants, depends on the surface charge of microplastics, and the functional groups modified on the surface of microplastics are the key factors affecting the toxicity of microplastics. Since the toxicity of microplastics to plants mainly depends on the charge on their surface; and in combination with reality, most microplastics in the environment are charged with functional groups, so the present invention preferably uses polystyrene with functional groups for research.

[0010] Preferably, the size of the microplastics is 20-80 nm.

[0011] It should be noted that the present invention conducted experiments on Arabidopsis thaliana, a commonly used model plant in the laboratory, to verify the role of Mn3O4 nanofertilizer in alleviating the inhibition of microplastic particles on plant growth. Therefore, the application of the present invention is not limited to Arabidopsis thaliana, which should be clear to those skilled in the art.

[0012] Preferably, the organic and / or inorganic fertilizer is liquid fertilizer or solid fertilizer.

[0013] Preferably, the plant growth inhibition refers to the effect on plant root length, fresh weight and / or photosynthesis.

[0014] Mn is one of the essential elements for plant photosynthesis. A moderate concentration of Mn can promote seed germination and seedling growth, and is one of the indispensable trace elements in plant growth and development. Mn3O4 nanoparticles are small in size, can release manganese ions cyclically, and have good stability in water. The inventors found that PS exerts stress on plant growth, producing H2O2, ·OH, ·O 2- Various ROS (reactive oxygen species) such as free radicals inhibit plant growth and photosynthesis; Mn3O4 is used as a nanofertilizer, and the addition of Mn3O4 eliminates various ROS produced by PS, thus alleviating PS stress.

[0015] The Mn3O4 nanofertilizer in this invention can be used as a nanofertilizer to alleviate the stress caused by PS on plant roots and photosynthesis. Because plant roots are highly sensitive to external stimuli, the Arabidopsis thaliana used in the series of experiments was germinated and grown in culture dishes. The method first creates a stress on the Arabidopsis thaliana growth process by applying PS-NH2 and PS-SO3H to the culture dishes during the germination stage of the Arabidopsis seeds. The PS stress is then alleviated by applying a certain amount of Mn3O4 nanofertilizer. The physiological mitigation effect on the Arabidopsis thaliana was determined using root length and aboveground fresh weight, while photosynthetic efficiency was analyzed using chlorophyll fluorescence data.

[0016] The PS stress induced by the present invention involves the effects of two PS nanoparticles (PS-NH2 and PS-SO3H) with different surface charges (positive and negative) on plant growth. The PS nanoparticles can be prepared using a variety of methods, such as microemulsion polymerization, and are not particularly limited in this invention. Preferably, the size of the positively charged PS-NH2 is 60 nm, while the size of the negatively charged PS-SO3H is 40 nm.

[0017] In the present invention, there are multiple methods for preparing the Mn3O4 nanoparticles, all of which are commonly used methods for synthesizing nanomaterials, such as solvent thermal method, microemulsion method, mechanical ball milling method, etc. However, the purpose of the present invention is to prove that Mn3O4 has a mitigating effect on PS with both positive and negative surface charges, so commercially available Mn3O4 nanoparticle materials can also be used in the present invention.

[0018] The present study found that PS stress on root growth and photosynthesis parameters in Arabidopsis thaliana was alleviated to a certain extent by various Mn3O4 concentrations. When exposed to PS at a concentration of 100 μg / mL, Mn3O4 at concentrations of 50-200 μg / mL or 50-200 μg / g significantly alleviated the stress, with the optimal Mn3O4 concentrations being 100-200 μg / mL or 100-200 μg / g.

[0019] The present invention applies Mn3O4 to Arabidopsis plants under PS stress, confirming its stress-relieving effect. First, the stress effect of PS on Arabidopsis growth and the promoting effect of Mn3O4 were visually compared using a root length phenotype. Root length and fresh weight were further observed. The Fv / Fm ratio of Arabidopsis plants decreased under PS stress, while the application of Mn3O4 alleviated this PS-induced stress. In particular, the application of Mn3O4 increased the transient fluorescence and chlorophyll fluorescence parameters of Arabidopsis leaves under PS stress, ultimately promoting growth and improving photosynthesis efficiency.

[0020] This invention uses small-sized Mn3O4 nanofertilizers to alleviate PS stress during the growth of Arabidopsis thaliana, providing a convenient and effective stress-mitigation solution. Since plants / crops are the cornerstone of the food chain, when PS residual in agricultural soil accumulates and internalizes within the plants / crops, it poses a threat to their yield, quality, and safety, ultimately entering the human body and endangering human health. This invention not only responds to the Ministry of Agriculture and Rural Affairs' call for the vigorous development of green fertilizers, but also provides a new, sustainable, green, and healthy approach to alleviating PS-stressed plant / crop growth. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 PS-NH2 ( Figure 1 a), PS-SO3H ( Figure 1 b) Mn3O4 ( Figure 1 c) Transmission electron microscopy image;

[0022] Figure 2 This is Example 3 of the present invention ( Figure 2 a) Example 4 ( Figure 2 b) Example 5 ( Figure 2 c) A comparative diagram of Arabidopsis root length phenotypes provided;

[0023] Figure 3 This is Example 3 of the present invention ( Figure 3 a) Example 4 ( Figure 3 b) Example 5 ( Figure 3 c) The provided diagram of Arabidopsis root length analysis;

[0024] Figure 4 This is Example 3 of the present invention ( Figure 4 a) Example 4 ( Figure 4 b) Example 5 ( Figure 4 c) The provided figure of Arabidopsis fresh weight analysis;

[0025] Figure 5 This is Example 4 of the present invention ( Figure 5 a) Example 5 ( Figure 5 b. Figure 5 c) Fv / Fm analysis of Arabidopsis leaves provided;

[0026] Figure 6 This is Example 4 of the present invention ( Figure 6 a) Example 5 ( Figure 6 b. Figure 6 c) Transient fluorescence parameters of Arabidopsis leaves provided;

[0027] Figure 7This is Example 4 of the present invention ( Figure 7 a) Example 5 ( Figure 7 b, 7c) Chlorophyll fluorescence parameter analysis diagrams of Arabidopsis leaves provided;

[0028] FIG8 is a diagram of embodiment 4 of the present invention ( Figure 8a )、Example 5( Figure 8b 、 Figure 8c ) Radar chart of chlorophyll fluorescence parameters of Arabidopsis leaves provided by . DETAILED DESCRIPTION

[0029] The following embodiments are further descriptions of the present invention to illustrate the technical content of the present invention, but the essential content of the present invention is not limited to the following embodiments. Ordinary technicians in this field can and should know that any simple changes or replacements based on the essential spirit of the present invention should fall within the scope of protection required by the present invention.

[0030] Example 1

[0031] 1. Preparation of PS-NH2 nanoparticles with amino groups, comprising the following steps:

[0032] Dissolve 0.5 g of styrene and 0.2 g of dodecyl sulfate (emulsifier) in 9 mL of deionized water and pre-emulsify with magnetic stirring for 1 hour to obtain a mixture. This mixture is then thoroughly mixed with 0.6 g of potassium persulfate (initiator), which has been pre-emulsified for 1 hour, at 50°C. The mixture is hydrothermally dissolved at 80°C under nitrogen for 5 hours. The mixture is then dialyzed using a 1 kDa dialysis tubing for 3-5 days to obtain positively charged PS-NH2.

[0033] The prepared PS-NH2 nanoparticles are 60 nm in size and positively charged.

[0034] 2. Preparation of PS-SO3H nanoparticles with sulfonic acid groups, comprising the following steps:

[0035] Dissolve 0.5 g of styrene, 2 g of 2-aminoethyl ester hydrochloride, and 0.6 g of dodecylamine hydrochloride (emulsifier) in 9 mL of deionized water and pre-emulsify with magnetic stirring for 1 hour to obtain a mixture. This mixture was then mixed with 0.5 g of 2,2'-azobisisobutylnitrile (initiator), which had been pre-emulsified for 1 hour, at 50°C. The mixture was hydrothermally dissolved at 80°C under nitrogen for 5 hours. The mixture was then dialyzed using a 1 kDa dialysis tubing for 3-5 days to obtain negatively charged PS-SO3H.

[0036] The prepared PS-SO3H nanoparticles are 40 nm in size and negatively charged.

[0037] Example 2

[0038] The preparation method of Mn3O4 nanoparticles comprises the following steps:

[0039] 0.408 g of manganese acetate was thoroughly dissolved in 20 mL of anhydrous ethanol (magnetically stirred for 20 minutes) to obtain a pink mixture. The mixture was transferred to a polytetrafluoroethylene reactor and heated at 120°C for 24 hours. After the reaction was complete, the brown solution was cooled to room temperature and transferred to a centrifuge tube. The solution was washed three times with ethanol and deionized water (centrifuged at 12,000 rpm for 10 minutes) and finally dispersed in deionized water to obtain Mn3O4 nanoparticles. The prepared Mn3O4 nanoparticles were 10 nm in size.

[0040] Example 3

[0041] Determination of the effects of PS on root length and photosynthesis in Arabidopsis thaliana.

[0042] 1. Preparation of MS medium

[0043] Prepare the solution in a 200 mL glass bottle: First, weigh 0.46 g 1 / 2MS and 2 g sucrose and dissolve them in 200 mL of deionized water. Ultrasonicate to dissolve thoroughly. Then weigh 2.4 g agar and dissolve thoroughly. Adjust the pH of the solution to 5.7-5.9 and sterilize by autoclaving at 121°C for 30 min.

[0044] 2. Treatment of Arabidopsis seeds with different concentrations of PS

[0045] Add 50, 100, and 200 μg / mL of PS-NH2 and PS-SO3H to the culture medium, respectively, and use a blank culture medium as a control group; cool until solidified and set aside.

[0046] 3. Disinfection, Sowing and Germination of Arabidopsis Seeds

[0047] The present invention uses Col-0 Arabidopsis thaliana. Before sowing, the seeds are first sterilized by soaking and blowing in 75% ethanol for 1 minute and then washing with sterile water 2-3 times. They are then sterilized by soaking in 5% NaClO for 6-8 minutes and then washing with sterile water 2-3 times.

[0048] Use toothpicks to evenly spot Arabidopsis seeds on the culture medium and seal with parafilm. Place the spotted seeds in a 4°C refrigerator for 2 days for vernalization. Then, transfer them to a growth chamber at 20°C, 6000 lux, 68% humidity, and 16 h light / 8 h dark for 8 days.

[0049] 4. Determination of Arabidopsis Root Length

[0050] Arabidopsis seedlings that had been vernalized for 2 days and cultured for 8 days had their roots straightened with tweezers. A standard ruler was placed parallel to the seedlings and photographed. The root lengths were measured using Image J based on the length of the standard ruler. The average root length for each group of samples was calculated, and the Arabidopsis seedlings with the closest root length to the average were transferred to the same plate to observe the effects of different PS concentrations on Arabidopsis root length. The specific results are shown in the figure. Figure 2 、 3 As shown. Figure 2 The provided Arabidopsis root length phenotype diagram, Figure 2 (a) It can be seen that PS-NPs have a certain inhibitory effect on the growth of Arabidopsis root length, and the inhibitory effect of PS-SO3H is slightly stronger than that of PS-NH2. Figure 3 What is shown is Figure 2 The corresponding specific parameters of Arabidopsis root length.

[0051] 5. Determination of Arabidopsis Fresh Weight

[0052] Select 10 Arabidopsis seedlings with similar growth status and weigh them to observe the effect of different concentrations of PS on the fresh weight of Arabidopsis. The specific results are as follows: Figure 4 As shown. Figure 4 (a) It can be seen that both positively and negatively charged PS-NPs had a certain inhibitory effect on the fresh weight of Arabidopsis thaliana, and the higher the concentration of PS-NPs, the more obvious the inhibition on the fresh weight of Arabidopsis thaliana.

[0053] 6. Determination of Arabidopsis Chlorophyll Fluorescence Parameters

[0054] Five intact leaves of uniform size were cut from Arabidopsis seedlings of similar growth conditions and treated in the dark for 20 minutes. A Yaxin-1161G portable fluorometer (Beijing Yaxin Instrument Technology Co., Ltd.) was used to measure chlorophyll fluorescence kinetic parameters, including the maximum photochemical quantum yield of PSII (Fv / Fm), OJIP curve parameters (transient fluorescence parameters), electron transport rate (ETR), fluorescence quantum yield of photosynthetic system II (φPSII), photochemical quenching constant (qP), non-photochemical quenching constant (qPN), specific activity parameters, and performance index.

[0055] Example 4

[0056] Determination of the effects of Mn3O4 nanoparticles on root growth and photosynthesis in Arabidopsis thaliana.

[0057] 1. Preparation of MS medium

[0058] Same as Example 3.

[0059] 2. Treatment of Arabidopsis seeds with different concentrations of Mn3O4

[0060] Add 50, 100, and 200 μg / mL of Mn3O4 to the culture medium, respectively, and use a blank culture medium as a control group; cool until solidified and set aside.

[0061] 3. Disinfection, Sowing and Germination of Arabidopsis Seeds

[0062] Same as Example 3.

[0063] 4. Determination of Arabidopsis Root Length

[0064] Same as Example 3. Figure 2 (b) It can be seen that Mn3O4-NP has a certain promoting effect on the root length of Arabidopsis thaliana. Figure 3 What is shown is Figure 2 The corresponding specific parameters of Arabidopsis root length.

[0065] 5. Determination of Arabidopsis Fresh Weight

[0066] Same as Example 3. Figure 4 (b) It can be seen that 100 μg / mL of Mn3O4-NP has the strongest promoting effect on the fresh weight of Arabidopsis; while 200 μg / mL of Mn3O4-NP has a promoting effect on the fresh weight of Arabidopsis, the promoting effect is significantly lower than 100 μg / mL, which may be due to the fact that the supersaturated Mn causes a certain load on the roots of Arabidopsis.

[0067] 6. Determination of Arabidopsis Chlorophyll Fluorescence Parameters

[0068] Same as Example 3. Figure 5 The Fv / Fm value of Arabidopsis photosynthesis parameters is shown. Generally speaking, when Fv / Fm is around 0.7, it is considered that the plant is not under stress. Figure 5 (a) It can be seen that Mn3O4-NP did not cause stress to Arabidopsis. Figure 6 The OJIP curve of plant photosynthesis parameters is shown. Arabidopsis seedlings are first adapted to a dark environment for 20 minutes, and then pulse instantaneous fluorescence detection is performed. The total detection time is generally ≥150 seconds. Among them, Fj is the fluorescence at 2 ms of illumination after dark adaptation (point J), Fi is the fluorescence at 30 ms of illumination after dark adaptation (point I), and Fp is the fluorescence intensity at the maximum fluorescence (point P). Figure 6 (a) It can be seen that when Mn3O4 is used alone as a nanofertilizer, its concentration of 50-100 μg / mL has a more obvious promoting effect on the transient fluorescence parameters of Arabidopsis OJIP. Figure 7is the pulse transient fluorescence curve parameter of plant photosynthesis, where: ETR is the electron transfer rate, ΦPSII is the fluorescence quantum yield of photosynthetic system II, qP is the photochemical quenching constant (an increase in qP indicates an increase in the conversion of light energy absorbed by PSII into photochemical energy), and qNP is the non-photochemical quenching constant (a decrease indicates a decrease in lost energy). Figure 7 (a) It can be seen that when Mn3O4 is used alone as a nanofertilizer in Arabidopsis, the ETR coefficient increases with the increase of nanofertilizer concentration. ΦPSII and qP have no obvious change trend overall, and qNP decreases slightly, indicating that Mn3O4 can promote photosynthesis in Arabidopsis seedlings when used as a nanofertilizer. Figure 8 shows the specific activity parameters and performance indexes in photosynthesis, where ABS / RC is the light energy absorbed per unit reaction center, TR o / RC is the energy captured by the reaction center for reducing QA, ET o / RC is the energy captured by the reaction center for electron transfer, ABS / CS m is the light energy absorbed per unit area, TR o / CS m is the light energy captured per unit area, ET o / CS m is the quantum yield of electron transfer per unit area, PI ABS This performance index is based on the absorption of light energy. Figure 8(a) shows that when Mn₃O₄ is used alone as a nanofertilizer, its effect on promoting photosynthesis in Arabidopsis seedlings increases with increasing concentration. Overall, Mn₃O₄ as a nanofertilizer has a promoting effect on Arabidopsis photosynthesis.

[0069] Example 5

[0070] Arabidopsis seeds were exposed to 100 μg / mL PS-NH2 and PS-SO3H stress and treated with different concentrations of Mn3O4, and the root length and photosynthesis of Arabidopsis were measured.

[0071] 1. Preparation of MS medium

[0072] Same as Example 3.

[0073] 2. Apply PS stress to Arabidopsis

[0074] 100 μg / mL of PS-NH2 and PS-SO3H were added to the culture medium and set aside.

[0075] 3. Apply Mn3O4 to Arabidopsis under PS stress

[0076] 50, 100, and 200 μg / mL of Mn3O4 were added to the above-mentioned PS medium with 100 μg / mL, respectively, and a blank medium was used as a control group; the medium was cooled to solidify and set aside.

[0077] 4. Disinfection, Sowing and Germination of Arabidopsis Seeds

[0078] Same as Example 3.

[0079] 5. Determination of Arabidopsis Root Length

[0080] Same as Example 3. Figure 2 (c) Shows the alleviating effect of Mn3O4-NP on Arabidopsis root length at 100 μg / mL of PS-NPs. It can be seen that Mn3O4-NP has the best alleviating effect on root length at 100 μg / mL. Figure 3 What is shown is Figure 2 The corresponding specific parameters of Arabidopsis root length.

[0081] 6. Determination of Arabidopsis Fresh Weight

[0082] Same as Example 3. Figure 4 (c) The alleviating effects of 50, 100, and 200 μg / mL of Mn3O4-NP on the fresh weight of Arabidopsis were investigated under the stress of 100 μg / mL of PS-NH2 and PS-SO3H, respectively. It can be seen that 100 μg / mL of Mn3O4-NP had the best alleviating effect on the fresh weight of Arabidopsis.

[0083] 7. Determination of Arabidopsis Chlorophyll Fluorescence Parameters

[0084] Same as Example 3. Figure 5 (b) It can be seen that due to Fv / Fm<0.7, 100 μg / mL PS-NH2 exerted a certain stress on the growth of Arabidopsis, and the addition of Mn3O4-NP could alleviate the stress caused by PS-NH2. Figure 5 (c) It can be seen that due to Fv / Fm<0.7, the growth of PS-SO3H Arabidopsis produced a certain stress, and the addition of Mn3O4-NP can alleviate the stress caused by PS-SO3H. This may be because PS produces H2O2, ∙OH and O2 during the growth of Arabidopsis. ·- Mn3O4-NPs with catalase-like and superoxide dismutase-like activities can remove ROS produced by PS and alleviate the stress caused by PS on Arabidopsis. Figure 6(b) (c) It can be seen that PS-NH2-100 μg / mL and PS-SO3H-100 μg / mL both significantly inhibited the transient fluorescence of chlorophyll in Arabidopsis seedlings, and when Mn3O4 was added as nanofertilizer, 100 μg / mL of nanofertilizer had the best mitigating effect on PS-NH2 and PS-SO3H. Figure 7 (b) It can be seen that the addition of PS-NH2 significantly stressed the photosynthesis of Arabidopsis seedlings, and the addition of Mn3O4 effectively alleviated the stress; Figure 7 In (c), PS-SO₃H had little effect on the photosynthesis of Arabidopsis seedlings, possibly because PS-SO₃H is negatively charged and has relatively weak adsorption capacity on plant and Mn₃O₄ surfaces. Based on the increase in qP, it can be seen that Mn₃O₄ enhances the conversion of light energy absorbed by PSII into photochemical energy during photosynthesis in Arabidopsis seedlings under PS-SO₃H stress. Figures 8(b) and 8(c) show that both PS-NH₂ and PS-SO₃H inhibited Arabidopsis photosynthesis. The addition of Mn₃O₄ effectively ameliorated PS stress, with the best mitigation effect achieved at Mn₃O₄ concentrations of 100-200 μg / mL.

[0085] To ensure the observability of the experimental effects and considering the actual residual PS concentration in agricultural soil, the present invention selected 100 μg / mL of PS-NH2 and PS-SO3H as the optimal final concentration for exploring the effect of Mn3O4 nanofertilizers in alleviating PS stress. Preferably, using PS-NH2 and PS-SO3H as stress conditions, both inhibited Arabidopsis growth at concentrations of 50-200 μg / mL. Furthermore, the inhibitory effects of PS-NH2 and PS-SO3H on Arabidopsis growth increased with increasing concentrations. Furthermore, the stress effects of PS-NH2 on Arabidopsis root length and photosynthesis parameters were slightly lower than those of PS-SO3H.

[0086] In order to explore whether the synthesized Mn3O4 nanoparticles can promote the growth of Arabidopsis thaliana as a fertilizer, the present invention investigated the effects of Mn3O4 nanoparticles alone as a fertilizer on root length and photosynthesis during the germination period of Arabidopsis thaliana seeds. The Mn3O4 nanoparticles were applied at a concentration range of 50-200 μg / mL. The Mn3O4 nanoparticles were applied by thoroughly mixing Mn3O4 at different concentrations with liquid 1 / 2MS culture medium, pouring the medium onto a plate, streaking the plate, and then seeding the seeds. The Arabidopsis thaliana seeds were sterilized during the experiment. Mn3O4, as a nanofertilizer, at different concentrations all had a certain promoting effect on the root length and photosynthesis parameters of Arabidopsis thaliana. Mn3O4 at a concentration of 100-200 μg / mL had the best promoting effect on the root length and photosynthesis parameters of Arabidopsis thaliana.

[0087] To investigate the effects of varying concentrations of Mn3O4 nanofertilizer on the growth of Arabidopsis thaliana subjected to PS stress, the present invention provides a Mn3O4 nanofertilizer and its application for alleviating PS-NH2 and PS-SO3H stress on root growth and photosynthesis in Arabidopsis. The PS-NH2 and PS-SO3H stresses were applied at a concentration of 100 μg / mL. The Mn3O4 concentration ranged from 50 to 200 μg / mL. The application method for these materials was as follows: first, 100 μg / mL of PS-NH2 and PS-SO3H were applied to liquid 1 / 2 MS culture medium to induce PS stress; then, varying concentrations of Mn3O4 were applied and thoroughly mixed; then, plates were poured, streaked, and seeds were sown. Mn3O4 at varying concentrations showed a certain degree of mitigation effect on root growth and photosynthesis parameters in Arabidopsis thaliana. The study found that applying Mn3O4 to Arabidopsis thaliana under PS stress at a concentration of 100 μg / mL significantly alleviated the stress, with the optimal Mn3O4 concentration being between 100 and 200 μg / mL. Mn3O4, as a nanofertilizer, can alleviate PS stress on Arabidopsis growth and photosynthesis. This is likely because PS-SO3H generates various ROS, including H2O2, ∙OH, and ∙O2-, during the growth of Arabidopsis. Mn3O4-NPs, which possess catalase- and superoxide dismutase-like activities, can scavenge PS-generated ROS, thereby alleviating PS stress in Arabidopsis.

[0088] The present invention discloses for the first time the application of Mn3O4 nanofertilizer in alleviating the inhibition of plant growth by microplastic particles, wherein PS is used as a stress condition and Mn3O4 is used as a nanofertilizer. The effect of Mn3O4 on alleviating PS stress is demonstrated by means of phenotype, root length, fresh weight and photosynthesis parameter results. The present invention found that under PS stress, the root length and fresh weight of Arabidopsis thaliana were inhibited to a certain extent, while Mn3O4 alone as a nanofertilizer significantly increased the root length and fresh weight of Arabidopsis thaliana. Importantly, the present invention found that Mn3O4 can alleviate the stress of PS on the root length and fresh weight of Arabidopsis thaliana and promote the growth of Arabidopsis thaliana. In addition, when Fv / Fm is 0.7, Arabidopsis thaliana is considered to be stress-free. The present invention found that PS exerted stress on Arabidopsis thaliana, and Mn3O4 has the ability to alleviate PS stress. Importantly, the chlorophyll fluorescence-related parameters provided by the present invention demonstrate that Mn₃O₄ alleviates photosynthesis in Arabidopsis thaliana under PS stress, with 100-200 μg / mL of Mn₃O₄ showing the best mitigating effect. Therefore, the Mn₃O₄ nanofertilizer provided by the present invention has a mitigating effect on root growth and photosynthesis in Arabidopsis thaliana under PS stress, significantly promoting plant growth and development.

[0089] It should be noted that the technical contents of the present invention described above are only for the purpose of explaining and illustrating the technical essence of the present invention to enable those skilled in the art to understand the technical essence of the present invention. Therefore, the technical contents described above are not intended to limit the substantial protection scope of the present invention. The substantial protection scope of the present invention shall be based on the claims. Those skilled in the art should be aware that any modifications, equivalent substitutions, and improvements based on the substantial spirit of the present invention shall fall within the substantial protection scope of the present invention.

Claims

1. The application of Mn3O4 nanofertilizer in alleviating the inhibition of microplastic particles on plant growth, wherein the Mn3O4 nanofertilizer is an organic and / or inorganic fertilizer containing at least Mn3O4 nanoparticles, and the microplastics include at least one of polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyamide and their derivatives.

2. The use according to claim 1, characterized in that The size of the Mn3O4 nanoparticles is 8-20 nm.

3. The use according to claim 2, characterized in that The size of the Mn3O4 nanoparticles is 10-15 nm.

4. The use according to claim 1, wherein The microplastic is at least one of polystyrene and its derivatives.

5. The use according to claim 4, characterized in that The polystyrene derivative includes at least one of aminated polystyrene, sulfonated polystyrene, and carboxylated polystyrene.

6. The use according to claim 1, wherein The size of the microplastics is 20-80 nm.

7. The use according to claim 1, wherein The organic and / or inorganic fertilizer is liquid fertilizer or solid fertilizer.

8. The use according to claim 1, wherein The plant growth inhibition refers to the effect on the plant root length, fresh weight and / or photosynthesis.

9. The use according to claim 1, wherein In the Mn3O4 nanofertilizer, the concentration of Mn3O4 nanoparticles is 50-200 μg / mL or 50-200 μg / g.

10. The use according to claim 9, characterized in that The concentration of the Mn3O4 nanoparticles is 100 - 200 μg / mL or 100 - 200 μg / g.

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