Application of arbuscular mycorrhizal fungi in improving heavy metal stress resistance of poplar

Abstract

The invention belongs to the field of forestry, and particularly relates to application of arbuscular mycorrhizal fungi to improvement of heavy metal stress resistance of poplars, growth performance of the poplars is remarkably improved by inoculating the arbuscular mycorrhizal fungi, and net photosynthetic rate, stomatal conductance, transpiration rate, maximum photochemical quantum efficiency and effective photochemical efficiency of a photosystem II are remarkably improved. Under the condition of lead stress, the lead content in the leaves, stems and root systems of the poplar inoculated with the arbuscular mycorrhizal fungi is obviously reduced, which indicates that lead is mainly isolated in the root systems, and the transfer of lead to the overground part is reduced. In addition, the arbuscular mycorrhizal fungi relieve oxidative damage by improving the activity of antioxidant enzymes such as superoxide dismutase, catalase and peroxidase.

Description

Technical Field

[0001] The invention belongs to the field of forestry, and more specifically relates to the application of arbuscular mycorrhizal fungi in improving the resistance of poplars to heavy metal stress. Background Art

[0002] Heavy metal pollution is a widespread environmental problem worldwide. Among various heavy metals, lead is particularly troublesome because of its widespread presence and high persistence in the environment. Lead can disrupt key biological processes in plants, leading to slower growth, impaired photosynthesis, and increased oxidative stress. Phytoremediation technology has become a promising strategy to mitigate heavy metal pollution by using plants to remove or neutralize environmental pollutants.

[0003] Arbuscular mycorrhizae are referred to as AM in English. AM fungi have attracted much attention as a fungus that has many benefits for plants. AM fungi can absorb nutrients such as phosphorus, nitrogen, and potassium in the soil that are difficult for plants to absorb directly, and convert them into a form that can be used by plants for absorption and utilization. The arbuscular structure of arbuscular mycorrhizal fungi can expand the surface area of ​​plant roots, thereby increasing the plant's ability to absorb water. By symbiotically coexisting with plant roots, it can help plants absorb water from the soil more effectively and reduce water evaporation and loss, thereby improving the plant's drought resistance.

[0004] Poplar is considered an ideal candidate for phytoremediation due to its rapid growth and large biomass, but how to provide poplar with tolerance to heavy metal stress by arbuscular mycorrhizal fungi remains poorly understood. Summary of the invention

[0005] The invention aims to provide application of arbuscular mycorrhizal fungi in improving the resistance of poplar to heavy metal stress.

[0006] The above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0007] The invention provides application of arbuscular mycorrhizal fungi in improving the heavy metal stress resistance of poplars. The arbuscular mycorrhizal fungi are Heteromorpha rhizosporon, which are purchased from the Chinese arbuscular mycorrhizal fungi germplasm resource bank of Beijing Academy of Agriculture and Forestry Sciences and have a preservation number of BJ09.

[0008] The present invention significantly improves the growth and lead stress tolerance of poplars under lead stress by inoculating the arbuscular mycorrhizal fungus Heterosporium at the roots of poplars. After the inoculation of AM fungi, the growth and photosynthetic efficiency of the poplars are enhanced, the contents of hydrogen peroxide and malondialdehyde are reduced, and the activity of antioxidant enzymes is enhanced, which indicates that the AM fungi enhance the plant's intrinsic defense system against reactive oxygen and improve nutrition and photosynthesis.

[0009] Furthermore, the heavy metal is lead.

[0010] Furthermore, the arbuscular mycorrhizal fungi are used to improve the net photosynthetic rate, stomatal conductance, transpiration rate, maximum photochemical quantum efficiency of photosystem II and effective photochemical efficiency of poplar trees under heavy metal stress.

[0011] Furthermore, the arbuscular mycorrhizal fungi are used to improve the activities of superoxide dismutase, catalase and peroxidase in poplars under heavy metal stress.

[0012] Furthermore, the arbuscular mycorrhizal fungi are used to reduce the lead content in leaves, stems and roots of poplars under heavy metal stress.

[0013] Furthermore, the application is as follows:

[0014] S1. preparing arbuscular mycorrhizal fungal agent;

[0015] S2. Transplanting the poplar seedlings into sandy loam mixed with the arbuscular mycorrhizal fungal agent.

[0016] Furthermore, the specific steps of preparing the arbuscular mycorrhizal fungal agent described in S1 are as follows:

[0017] S11, inoculating the arbuscular mycorrhizal fungus Heterosporium heterorhizogenes into the roots of corn seedlings and culturing them in pure sand;

[0018] S12. After the corn has grown for 5 to 7 months, the corn roots are collected, the corn roots are cut into pieces and mixed with pure sand to obtain an arbuscular mycorrhizal fungal agent consisting of corn root segments, arbuscular mycorrhizal fungal hyphae, spores and pure sand.

[0019] Furthermore, the culture conditions of the arbuscular mycorrhiza in S11 are a temperature of 20° C. to 30° C. and a humidity of 70% to 80%.

[0020] Furthermore, the spore density in the S12 is 40 to 60 spores / g.

[0021] The present invention has the following beneficial effects:

[0022] The present invention provides a method for improving the resistance of poplar to heavy metal stress by using arbuscular mycorrhizal fungi, which significantly improves the growth performance of poplar through the interaction between plants and microorganisms, which is specifically reflected in the significant increase in plant height, aboveground biomass and root biomass. In addition, arbuscular mycorrhizal fungi significantly improve the net photosynthetic rate, stomatal conductance, transpiration rate, maximum photochemical quantum efficiency of photosystem II and effective photochemical efficiency. Under lead stress conditions, the lead content in leaves, stems and roots of poplars inoculated with arbuscular mycorrhizal fungi is significantly reduced, indicating that the lead is mainly isolated in the root system, reducing its transport to the aboveground part. In addition, arbuscular mycorrhizal fungi reduce oxidative damage by increasing the activity of antioxidant enzymes such as superoxide dismutase, catalase and peroxidase. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 This is a diagram showing the effect of AM fungi on the growth status of poplar under different lead concentrations, where A is the plant height diagram, B is the plant aboveground biomass diagram, and C is the underground biomass diagram.

[0025] Figure 2 The following is a diagram showing the effect of AM fungi on photosynthetic parameters of poplar under different lead concentrations, where A is the net photosynthetic rate, B is the intercellular CO2 concentration, C is the transpiration rate, and D is the stomatal conductance.

[0026] Figure 3 This is a graph showing the effect of AM fungi on the chlorophyll content of poplar trees under different lead concentrations.

[0027] Figure 4 The following are the effects of AM fungi on the fluorescence parameters of poplar chlorophyll under different lead concentrations, where A is the maximum photochemical quantum yield, B is the non-photochemical quenching, C is the photosynthetic electron transfer rate, and D is the effective photochemical efficiency.

[0028] Figure 5 The following is a diagram showing the effect of AM fungi on the lead content of poplar trees under different lead concentrations, where A is the lead content in leaves, B is the lead content in stems, and C is the lead content in roots.

[0029] Figure 6 The following are the effects of AM fungi on the transfer coefficient and bioaccumulation coefficient of poplar under different lead concentrations, where A is the transfer coefficient diagram and B is the enrichment coefficient diagram.

[0030] Figure 7 The figure shows the effect of AM fungi on the hydrogen peroxide and malondialdehyde content of poplar under different lead concentrations, where A is the hydrogen peroxide content graph and B is the malondialdehyde content graph.

[0031] Figure 8 These are the effects of AM fungi on poplar enzyme activity under different lead concentrations, where A is the peroxidase activity graph, B is the superoxide dismutase activity graph, and C is the glutathione content graph. DETAILED DESCRIPTION

[0032] The present invention is described in detail below in conjunction with the accompanying drawings and specific examples, but should not be construed as limiting the present invention. Unless otherwise specified, the technical means used in the following examples are conventional means well known to those skilled in the art, and the materials, reagents, etc. used in the following examples, unless otherwise specified, can be obtained from commercial sources.

[0033] The arbuscular mycorrhizal fungi in the following examples are Rhizophagus irregularis, purchased from the Chinese Arbuscular Mycorrhizal Fungi Germplasm Resource Bank of Beijing Academy of Agriculture and Forestry Sciences, with a deposit number of BJ09, which was published in the article "Inoculation with AMF improves soil microbial activity and drought resistance of oats under drought stress".

[0034] Example 1: Arbuscular mycorrhizal fungi affect poplar's resistance to heavy metal stress.

[0035] 1. Experimental methods

[0036] The poplar seedlings selected in the present invention are Populus simonii×P.nigra'1307', which is well-known for its fast growth and adaptation to environmental stress. The seedlings were inoculated with the arbuscular mycorrhizal fungus Heteromorpha rhizocystis. The experimental design mainly includes two groups: a control group that was not inoculated with arbuscular mycorrhizal fungi and a group that was inoculated with arbuscular mycorrhizal fungi. Both groups were exposed to four different concentrations of lead stress: 0 mg / kg, 250 mg / kg, 500 mg / kg and 750 mg / kg, and the selection of these concentrations was based on preliminary tests that showed phytotoxic effects and reflected typical environmental conditions at contaminated sites.

[0037] 1. Test microbial agent: The arbuscular mycorrhizal fungus Heteromorpha rhizosporium was purchased from the arbuscular mycorrhizal fungi germplasm resource bank of Beijing Academy of Agriculture and Forestry Sciences. The arbuscular mycorrhizal fungi spores were inoculated into the roots of corn seedlings at 80 spores / g, cultured in pure sand, and the strains were propagated. The corn roots were collected after 6 months of growth. The corn roots were chopped up with sterile scissors and mixed with pure sand to obtain a mixture of corn root segments, arbuscular mycorrhizal fungi hyphae, spores and pure sand as the test microbial agent, wherein the spore density was 52 spores / g.

[0038] 2. Soil preparation and characteristics: Local sandy loam soil was used in this experiment. River sand and vermiculite were purchased from Heilongjiang Academy of Agricultural Sciences. River sand was sterilized in an oven at 170℃ for 4h, and vermiculite was sterilized by high-pressure steam sterilization for 2h twice, 0.11MPa, 121℃, with an interval of 1h. River sand and vermiculite were mixed in a volume ratio of 1:1 and used as growth medium. The physical and chemical properties of the soil were pH = 7.98, total nitrogen content 0.835g / kg, available nitrogen 43.88mg / kg, available phosphorus 6.78mg / kg, available potassium 107.2mg / kg, organic matter 11.94g / kg, and total soluble salt 0.06%. The soil was sterilized at 121℃ for 30 minutes to eliminate local microorganisms and ensure that the observed effects could be fully attributed to the introduced arbuscular mycorrhizal fungi. There is a layer of pebbles at the bottom of the flowerpot, separated from the soil by two layers of newspaper. The test bacteria and sandy loam are evenly mixed in a mass ratio of 1:1 and then the poplar seedlings are transplanted. Each flowerpot is equipped with a polyvinyl chloride pipe for controlled irrigation.

[0039] 3. Plant growth conditions and treatments: Seedlings were maintained in a controlled greenhouse environment at 26°C, 65% relative humidity, and 16 h photoperiod. After a one-month acclimatization period, lead treatments were initiated and plants were grown for another 60 days. During this period, soil moisture content was measured regularly to ensure consistent hydration across all treatments.

[0040] 2. Sample testing

[0041] 1. Growth measurements: At the end of the treatment period, seedlings were harvested and divided into leaves, stems and roots. After drying the samples at 80 °C, fresh and dry biomass were recorded until a constant weight was reached. Plant height was measured from the base of the stem to the top of the apical bud.

[0042] 2. Photosynthetic parameters: The Ciras-3 portable photosynthesis system was used to evaluate photosynthetic performance. The measurements included net photosynthetic rate, stomatal conductance, transpiration rate, and intercellular carbon dioxide concentration. All measurements were performed at 1800 μmol·m -2 ·s -1 The light intensity and leaf temperature were standardized to 28 °C.

[0043] 3. Chlorophyll content and fluorescence analysis: After extracting 1 g of fresh leaf tissue in 80% acetone, chlorophyll a, chlorophyll b and total chlorophyll contents were quantified by spectrophotometry. The absorbance was measured at 665 nm and 649 nm, respectively. Chlorophyll fluorescence parameters, including the maximum photochemical quantum yield and effective photochemical efficiency of photosystem II, were evaluated using an FMS-2 fluorometer.

[0044] 4. Pb distribution and antioxidant enzyme activities: After acid digestion, the Pb concentration in leaves, stems and roots was determined by atomic absorption spectroscopy. The distribution of Pb within the plant was evaluated by calculating the transport coefficient and enrichment coefficient. The levels of hydrogen peroxide and malondialdehyde and the activities of superoxide dismutase, catalase and peroxidase were determined by standard biochemical analysis.

[0045] 3. Statistical analysis.

[0046] Data were statistically analyzed using ANOVA with Tukey post hoc test to determine significant differences between treatments. Significance was set at p < 0.05. Statistical analysis was performed using SPSS software version 23.0, and data visualization was performed using Sigma Plot version 12.5. All experiments were repeated three times, and the results are presented as mean ± standard deviation. AM in the figure indicates inoculated mycorrhizae, NM indicates uninoculated mycorrhizae, and significance between groups is marked by the ab method.

[0047] 4. Experimental results.

[0048] 1. Growth measurement: e.g. Figure 1 As shown in the figure, under the stress of 0mg / kg, 250mg / kg and 750mg / kg lead concentrations, inoculation with Heterosporangium promoted the growth of poplars, and the plant height, aboveground biomass and underground biomass of poplars were significantly higher than those of poplars not inoculated with Heterosporangium. As the lead treatment concentration increased, the plant height, aboveground biomass and underground biomass of non-inoculated mycorrhizal poplars all showed a downward trend. Figure 1 As shown in Figure B, the aboveground biomass of the inoculated mycorrhizal poplars was significantly higher than that of the non-inoculated mycorrhizal poplars under 750 mg / kg lead stress. Figure 1 As shown in C, the underground biomass of poplars inoculated with mycorrhizal roots was always significantly higher than that of non-inoculated mycorrhizal roots when subjected to 750 mg / kg lead stress.

[0049] 2. Photosynthetic parameters: such as Figure 2 As shown in Figure A, inoculation with Heterospora heterorhizogenes significantly improved the photosynthetic efficiency of poplars under Pb stress. Compared with non-inoculated mycorrhizal poplars, the net photosynthetic rate of inoculated mycorrhizal poplars was significantly increased. In contrast, the photosynthetic rate of non-inoculated mycorrhizal poplars decreased with increasing Pb concentrations.

[0050] like Figure 2 As shown in Figure B, the intercellular CO2 concentration of the inoculated mycorrhizal poplars decreased significantly under higher concentrations of lead stress, while the intercellular CO2 concentration of the non-inoculated mycorrhizal poplars increased when the lead stress concentration was 750 mg / kg. Figure 2 As shown in Figure C, under all Pb treatments, the transpiration rate of the inoculated mycorrhizal poplars was significantly higher than that of the non-inoculated mycorrhizal poplars, and a significant decrease was only observed under the lead stress of 750 mg / kg. Figure 2As shown in D, inoculation with mycorrhiza significantly increased stomatal conductance, especially under 0 mg / kg and 250 mg / kg Pb conditions, while the stomatal conductance of non-inoculated mycorrhizal poplar decreased with increasing Pb concentration.

[0051] As shown in Table 1, two-way ANOVA showed that both lead treatment and arbuscular mycorrhizal fungi inoculation had significant effects on these gas exchange parameters. With the increase of lead concentration, the physiological responses of both mycorrhizal and non-inoculated mycorrhizal poplars changed, especially at 750 mg / kg lead, indicating that the stress response mechanism was changed. Therefore, the subsequent analysis focused on the 0 mg / kg, 250 mg / kg and 750 mg / kg Pb treatments.

[0052] Table 1: Two-way ANOVA analysis of the effects of Pb treatment and AM fungi on photosynthetic parameters of poplar

[0053]

[0054] Note: Two-way ANOVA significant effect: *p<0.05; **p<0.01; ***p<0.001.

[0055] 3. Chlorophyll content: Figure 3 As shown in the figure, inoculation with the arbuscular mycorrhizal fungus Heterosporium had a significant effect on the concentration of photosynthetic pigments in poplars. Under the condition of 0 mg / kg lead, the concentrations of chlorophyll a, chlorophyll b and total chlorophyll in the plants inoculated with arbuscular mycorrhizal fungi increased, but there was no significant change in carotenoids. Among them, when treated with 750 mg / kg lead, the chlorophyll a of non-inoculated mycorrhizal poplars increased significantly by 84.17%. It is worth noting that the chlorophyll b between the inoculated mycorrhizal poplars was significantly different under the treatment of 750 mg / kg lead.

[0056] There was no significant difference in carotenoid concentration between plants inoculated with arbuscular mycorrhizal fungi and those not inoculated with arbuscular mycorrhizal fungi. In the 750 mg / kg lead treatment, the total chlorophyll content of the inoculated plants was higher.

[0057] 4. Fluorescence parameters: such as Figure 4 As shown in the figure, under lead stress, arbuscular mycorrhizal fungi also significantly increased the fluorescence parameters of poplar seedlings, including the maximum photochemical quantum yield and effective photochemical efficiency of photosystem II. Under 750 mg / kg lead treatment, the maximum photochemical quantum yield and effective photochemical efficiency values ​​of inoculated mycorrhizal poplars were significantly higher than those of non-inoculated groups.

[0058] Inoculation significantly affected the non-photochemical quenching of poplar. Compared with non-mycorrhizal poplar, the non-photochemical quenching of poplar inoculated with arbuscular mycorrhizal fungi was significantly reduced under 0mg / kg, 250mg / kg and 750mg / kg lead treatments.

[0059] As shown in Table 2, the results of two-way ANOVA showed that the inoculation treatment had a very significant effect on the maximum photochemical quantum yield of photosystem II and the effective photochemical efficiency of photosystem II. However, lead stress had no significant effect on the maximum photochemical quantum yield and effective photochemical efficiency. The interaction between inoculation and lead stress had a significant effect on the four indicators of poplar. The inoculation treatment had a significant effect on the photosynthetic electron transfer rate of poplar. Pb treatment had no significant effect on the photosynthetic electron transfer rate and non-photochemical quenching. The interaction between inoculation and lead treatment had a significant effect on the photosynthetic electron transfer rate.

[0060] Table 2: Two-way ANOVA analysis of the effects of Pb treatment and AM fungi on chlorophyll fluorescence parameters of poplar trees

[0061]

[0062] Note: NS, no statistically significant difference p>0.05; *p<0.05; **p<0.01; ***p<0.001.

[0063] Pb represents the Pb application rate, AM represents the AM fungus treatment, and Pb×AM represents the interaction between the AM fungus treatment and the Pb application rate.

[0064] 5. Lead content detection and analysis: Figure 5 As shown in Figure 2, lead treatment and inoculation with AMF significantly affected the lead content in leaves, stems, and roots of poplars. When the Pb concentration increased from 0 to 750 mg / kg, the lead content of non-inoculated AMF poplars increased in all tissues, while inoculation with AMF significantly reduced these levels. It is worth noting that under 250 mg / kg or 750 mg / kg lead treatment, the Pb content in the leaves of plants inoculated with AMF was not significantly different from the 0 mg / kg lead stress level of the control. At 250 mg / kg lead stress, there was no significant difference in the Pb content in the stems and roots of plants inoculated with AMF and those not inoculated.

[0065] 6. Transfer coefficient and enrichment coefficient analysis: Figure 6 As shown in the figure, lead stress and arbuscular mycorrhizal fungi inoculation had significant effects on the transfer coefficient and bioaccumulation factor of poplar. When the Pb concentration increased from 250 mg / kg to 750 mg / kg, the transfer coefficient and bioaccumulation factor of poplar inoculated with arbuscular mycorrhizal fungi showed a decreasing trend.

[0066] Compared with uninoculated poplars, inoculation with arbuscular mycorrhizal fungi significantly increased their transfer coefficient and enrichment coefficient under lead stress.

[0067] 7. Related enzyme activities: e.g. Figure 7As shown in Figure A, lead treatment and mycorrhizal inoculation significantly affected hydrogen peroxide concentrations. Hydrogen peroxide levels in non-inoculated mycorrhizal poplars increased under 250 mg / kg and 750 mg / kg lead treatments. However, in plants inoculated with arbuscular mycorrhizal fungi, there was no significant difference in hydrogen peroxide concentrations between these two Pb concentrations. At 750 mg / kg lead stress, hydrogen peroxide levels in plants inoculated with arbuscular mycorrhizal fungi were lower than those in non-inoculated mycorrhizal poplars.

[0068] like Figure 7 As shown in Figure B, the MDA levels of both the poplars inoculated with arbuscular mycorrhizal fungi and non-inoculated poplars increased significantly under 750 mg / kg lead treatment. Under 250 mg / kg lead stress, the MDA concentration of the plants inoculated with arbuscular mycorrhizal fungi was significantly lower than that of the non-inoculated plants.

[0069] like Figure 8 As shown in A, Pb treatment and arbuscular mycorrhizal fungi inoculation significantly affected peroxidase activity. In non-inoculated mycorrhizal poplars, the peroxidase activity in the stems was significantly reduced under 750 mg / kg lead stress. In all Pb treatments, the root peroxidase activity of inoculated mycorrhizal poplars was significantly higher than that of non-inoculated mycorrhizal poplars.

[0070] like Figure 8 As shown in Figure B, the superoxide dismutase activity in the roots of inoculated plants increased significantly under the treatments of 250 mg / kg and 750 mg / kg. In contrast, the superoxide dismutase activity in the branches of inoculated and non-inoculated plants decreased, but there was no significant difference. After inoculation with arbuscular mycorrhizal fungi, the superoxide dismutase activity in the roots of plants with a lead concentration below 0 mg / kg was significantly lower than that of non-inoculated plants.

[0071] like Figure 8 As shown in Figure C, the glutathione content of inoculated plants increased significantly under 750 mg / kg lead stress. Compared with non-inoculated mycorrhizal poplars, the glutathione levels in the shoots and roots of inoculated plants increased significantly under 0 mg / kg, 250 mg / kg and 750 mg / kg treatments.

[0072] The results showed that lead treatment had significant effects on hydrogen peroxide concentration, malondialdehyde concentration, and superoxide dismutase activity in roots, and on peroxidase activity in both leaves and roots. Inoculation with AM fungi had significant effects on hydrogen peroxide content, malondialdehyde, peroxidase activity, superoxide dismutase activity, and glutathione content, with particularly strong effects on glutathione levels in shoots and roots. However, the interactions between Pb treatment and inoculation with AMF were generally not significant, indicating that the combined presence of Pb and AMF did not significantly alter the individual effects of these factors on plant physiological and biochemical responses.

[0073] Although preferred embodiments of the present invention have been described, additional changes and modifications may be made to these embodiments by those skilled in the art once the basic inventive concepts are known. Obviously, various changes and modifications may be made to the present invention by those skilled in the art without departing from the spirit and scope of the present invention. Thus, the present invention is intended to include such changes and modifications if they fall within the scope of the claims and their equivalents.

Claims

1. The application of arbuscular mycorrhizal fungi in improving the resistance of poplar to heavy metal stress, characterized in that: The arbuscular mycorrhizal fungus is Rhizophagus irregularis, which is deposited in the Chinese Arbuscular Mycorrhizal Fungi Germplasm Resource Bank of Beijing Academy of Agriculture and Forestry Sciences with a deposit number of BJ09.

2. The use of arbuscular mycorrhizal fungi in improving the resistance of poplar to heavy metal stress according to claim 1, characterized in that: The heavy metal is lead.

3. The use of arbuscular mycorrhizal fungi in improving the resistance of poplar to heavy metal stress according to claim 1, characterized in that: The arbuscular mycorrhizal fungi are used for improving the net photosynthetic rate, stomatal conductance, transpiration rate, maximum photochemical quantum efficiency of photosystem II and effective photochemical efficiency of poplar trees under heavy metal stress.

4. The use of arbuscular mycorrhizal fungi in improving the resistance of poplar to heavy metal stress according to claim 1, characterized in that: The arbuscular mycorrhizal fungi are used for improving the superoxide dismutase, catalase and peroxidase activities of poplars under heavy metal stress.

5. The use of arbuscular mycorrhizal fungi in improving the resistance of poplar to heavy metal stress according to claim 1, characterized in that: The arbuscular mycorrhizal fungi are used to reduce the lead content in leaves, stems and roots of poplars under heavy metal stress.

6. The use of arbuscular mycorrhizal fungi in improving the resistance of poplar to heavy metal stress according to claim 1, characterized in that: The application is as follows: S1. preparing arbuscular mycorrhizal fungal agent; S2. Transplanting the poplar seedlings into sandy loam mixed with the arbuscular mycorrhizal fungal agent.

7. The use of arbuscular mycorrhizal fungi in improving the resistance of poplar to heavy metal stress according to claim 6, characterized in that: In S1, the specific steps of preparing the arbuscular mycorrhizal fungal agent are as follows: S11, inoculating the arbuscular mycorrhizal fungus Heterosporium heterorhizogenes into the roots of corn seedlings and culturing them in pure sand; S12. After the corn has grown for 5 to 7 months, the corn roots are collected, the corn roots are cut into pieces and mixed with pure sand to obtain an arbuscular mycorrhizal fungal agent consisting of corn root segments, arbuscular mycorrhizal fungal hyphae, spores and pure sand.

8. The use of arbuscular mycorrhizal fungi in improving the resistance of poplar to heavy metal stress according to claim 7, characterized in that: In S11, the culture temperature is 20°C to 30°C, and the humidity is 70% to 80%.

9. The use of arbuscular mycorrhizal fungi in improving the resistance of poplar to heavy metal stress according to claim 7, characterized in that: In S12, the spore density of the arbuscular mycorrhizal fungal agent is 40 to 60 spores / g.

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