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Article

Effect of Arbuscular Mycorrhiza Fungus Diversispora eburnea Inoculation on Lolium perenne and Amorpha fruticosa Growth, Cadmium Uptake, and Soil Cadmium Speciation in Cadmium-Contaminated Soil

by
Jiahua Sun
1,2,
Qiong Jia
1,2,
Yi Li
1,2,
Kanglong Dong
1,
Shuai Xu
1,
Yanan Ren
1,
Ting Zhang
1,
Jiayuan Chen
1,
Nannan Shi
1,2,* and
Shenglei Fu
1,2,3,*
1
College of Geography and Environmental Science, Henan University, Kaifeng 475004, China
2
Key Laboratory of Geospatial Technology for the Middle and Lower Yellow River Regions, Henan University, Ministry of Education, Kaifeng 475004, China
3
Dabieshan National Observation and Research Field Station of Forest Ecosystem, Henan University, Kaifeng 475004, China
*
Authors to whom correspondence should be addressed.
Int. J. Environ. Res. Public Health 2023, 20(1), 795; https://doi.org/10.3390/ijerph20010795
Submission received: 7 November 2022 / Revised: 18 December 2022 / Accepted: 23 December 2022 / Published: 1 January 2023
(This article belongs to the Section Environmental Health)
Browse Figures
Review Reports Versions Notes

Abstract

:
Cadmium (Cd) pollution has become aggravated during the past decades of industrialization, severely endangering human health through its entry into the food chain. While it is well understood that arbuscular mycorrhizal fungi (AMF) have a strong ability to regulate plant growth and Cd uptake, studies investigating how they affect soil Cd speciation and influence Cd uptake are limited. We designed a pot experiment comprising two AMF-inoculant groups (inoculation with Diversispora eburnea or no inoculation), three Cd concentration levels (0, 5, and 15 mg/kg), and two plant species (Lolium perenne and Amorpha fruticosa) to study the effect of AMF Diversispora eburnea on plant growth, Cd uptake, and Cd speciation in the soil. The results revealed that L. perenne exhibited higher productivity and greater Cd uptake than A. fruticosa, regardless of AMF D. eburnea inoculation. However, AMF D. eburnea significantly altered soil Cd speciation by increasing the proportion of exchangeable Cd and decreasing residual Cd, resulting in Cd enrichment in the plant root organs and the elimination of Cd from the polluted soils. Our experiments demonstrate that inoculating plants with AMF D. eburnea is an effective alternative strategy for remediating Cd-contaminated soil.

1. Introduction

With the rapid increase in the rate of industrialization, increasing amounts of waste gas, waste water, and waste residue that frequently contain heavy metals are being discharged from industries [1,2,3]. The heavy metal cadmium (Cd) has attracted considerable attention because of its strong mobility and high toxicity. Reports from multiple countries (including Japan and China) have shown that Cd enters the human body through the food chain, where it can cause renal dysfunction and other diseases [4,5,6]. Physical and chemical methods are commonly used in Cd remediation [7], but the costs involved in the processes and the adverse effects they have on soil biological properties have caused controversy, and their residues can cause secondary pollution [8,9]. Therefore, biotechnological solutions, such as phytoremediation, are favored because they are environmentally friendly and do not require the use of high-cost technology [10].
Arbuscular mycorrhizal fungi (AMF) are an important functional group of soil microorganisms that can form a symbiotic relationship with 80% of vascular plant species in terrestrial ecosystems [11]. Previous studies have shown that AMF play an active role in removing Cd from soil [12,13], as AMF mycelium significantly increase the absorption of mineral ions (such as phosphorus) and water in plants, which increases the plant biomass, and previous studies have shown that AMF play an active role in removing Cd from soil [14,15,16]. The symbiosis between AMF and plants improved the activity of antioxidant enzymes in plants, which reduces the Cd toxicity [17,18,19]. Furthermore, Wang et al. (2020) found that AMF can change the form of soil Cd, and increase the acid-soluble Cd content, which assists in the removal of soil Cd by plants [20]. Other studies have found that AMF may promote the retention of Cd in the roots, which reduces the transfer of Cd to the shoots of plants through the fixation and isolation of Cd [21,22]. AMF colonization can also enhance plant resistance to Cd by altering the subcellular distribution and chemical forms of Cd in plants [23,24].
Diversispora eburnea (D. eburnea) is an AMF species commonly found in the Cd mine tailings and it has promising potential for use in heavy metal remediation in soil [25,26]. Lolium perenne and Amorpha fruticosa are fast-growing plants that have a wide distribution, and they can be strongly enriched in Cd [27,28]. Their synergistic effect with AMF Diversispora [29,30] is known to be beneficial for soil Cd pollution remediation [31,32]. In addition, AMF can provide an abundant supply of phosphorus to Amorpha fruticosa during nitrogen fixation [33,34]. Therefore, it is likely that compared with Lolium perenne, its growth would be comparatively more improved with AMF under Cd stress.
The aim of this study was to investigate the effect of D. eburnean on the growth, accumulation, and transfer of Cd in Lolium perenne and Amorpha fruticosa, as well as the associated changes in Cd chemical species in the soil. We hypothesized that AMF D. eburnea inoculation would promote Cd uptake and accumulation by promoting plant biomass and changing the form of Cd within the soil. The results obtained here can enhance our understanding of the mechanisms involved in combining D. eburnea with plants to remediate Cd-contaminated soil.

2. Materials and Methods

2.1. Soil Preparation

The original topsoil (0–20 cm depth) was collected from the campus of Henan University, China (34°49′3″ N, 114°18′38″ E). The parent material of the soil is Yellow River alluvium, and the soil type is predominantly yellow fluvio-aquic soil with a sandy loam texture. The soil used to be a farmland and it has been abandoned since 2015. The soils were passed through a 2 mm sieve to remove stones and plants and mixed with sand (1:1, v:v). The mixed soils were then autoclaved at 121 °C for 2 h to remove live AMF spores. Cd chloride solution was added based on the dry weight of the soil to attain Cd concentrations of 0, 5, and 15 mg/kg in the soil. The soils were then mixed thoroughly and placed in equilibrium for one month to stabilize their chemical properties. Table 1 shows the separate parameters of the soil and sand prior to mixing and conducting the pot experiment.

2.2. Host Plants and AMF Inocula

Two plant species, L. perenne and A. fruticosa, were selected for use in this study. Their seeds were provided by the Muyang Gramineae Seed Technology Limited Company, China. The plant seeds were surface-sterilized in 75% alcohol (v:v) for 5 min before being rinsed five times with distilled water. They were then placed on wet filter paper in a Petri dish for germination. The AMF species D. eburnea used in the present study was supplied by the Bank of Glomeromycota in China, Beijing Academy of Agriculture and Forestry, China ([BGC] HK02C). The inoculum was obtained after six months of co-culture with corn (Zea mays L.) in autoclaved sand/vermiculite (1:1, v:v). It comprised a mixture of spores (40 spores g−1 inoculum), mycelia, root fragments, and soil.

2.3. Experimental Design

The experiment used a 2 × 3 × 2 factorial design with two plant species (L. perenne and A. fruticosa), three levels of Cd concentration (0, 5, and 15 mg/kg), and two AMF treatments (D. eburnea and a non-mycorrhizal control) in a completely randomized design. Each treatment had four replicates, yielding a total of 48 units (pots). Each plastic pot (upper diameter, 14 cm; lower diameter, 10 cm; height, 10 cm) was filled with 1 kg of soil. Before sowing the seeds, 30 g mycorrhizal inoculum (approximately 1200 spores) and soil were mixed and placed in a pot. For the non-mycorrhizal control treatment, 30 g of sterilized mycorrhizal inoculum was added.
A 10 mL AMF-free filtrate was applied to minimize differences in microbial communities between mycorrhizal and non-mycorrhizal pots. Thirty germinated seeds of L. perenne or ten germinated seeds of A. fruticosa were sown in each pot. After two weeks of germination, thinning was performed, leaving 15 seedlings for L. perenne and 5 seedlings for A. fruticosa. Seedlings were arranged under natural light and temperature conditions in a greenhouse and irrigated with tap water to maintain the soil at a water holding capacity of 70% during the growing period. The greenhouse temperature ranged from 18 °C to 34 °C during the day. For the first two weeks, pots received 10 mL of a full-strength Hoagland nutrient solution per week and were rotated weekly (Table S1) [35]. The greenhouse pot experiments began on 23 August 2020, and ended on 22 October 2020.

2.4. Harvest and Measurements

At harvest, the plant shoots and roots were harvested separately. Roots were thoroughly cleaned with tap water to remove attached soil particles and then carefully cleaned with deionized water. Shoots and one root subsample were dried at 70 °C for 72 h and weighed. The AMF infection rate was determined using the other root subsample, and root biomass was calculated using the ratio of fresh and dry root weights. To determine the Cd concentration in the plants, the dried shoots and roots were ground and digested with HNO3–HClO4 (4:1, v:v). The digestion solution was fixed to 25 mL with 2% HNO3 and filtered after acid removal, and the Cd content was determined using graphite furnace atomic absorption spectrometry (GF-AAS, Perkin Elmer, Waltham, MA, USA). Soil pH was measured using a pH meter in a 1:2.5 (w:v) suspension of soil and deionized water. The NH4+-N and NO3−-N concentrations were measured using dual wavelength spectrophotometry and the indophenol blue method, and quantified using SmartChem 200 discrete auto analyzer (AMS Group Westco, Rome, Italy). Available phosphorus (A-P) was extracted using 0.5 M NaHCO3 at a pH of 8.5 and quantified using the SmartChem 200 discrete auto analyzer. The activities of soil alkaline phosphatase and neutral phosphatase were determined using respective assay kits (Solarbio, Beijing, China, BC0285, and BC0465). Soil Cd was separated into exchangeable Cd (1 M MgCl2, 2 h), carbonate bound Cd (1 M CH3COONa, 2 h), Fe-Mn oxide bound Cd (0.05 M NH2OH·HCl, 5 h), organic-bound Cd (0.02 M HNO3; 3.2 M NH4Ac, 2 h) and residual Cd (HF, HClO4 and HCl, high-purity, 0.5 h) fractions using Tessier’s five step extraction method [36]. Then, the contents of different Cd fractions were determined using GF-AAS.
The AMF structure of the roots was stained according to the improved Kormanik, method [37]. The cleaned fresh root segments (1 cm slices, 50 fragments randomly selected for each sample) were decolorized in 10% KOH solution (92 °C, 30 min). Roots were acidified with 2% HCl solution at 20 °C for 5 min and stained with 0.05% acid fuchsin solution (92 °C, 20 min). After the root fragments were stained, slides were prepared for observation. The structures of AM fungi in roots, such as arbuscule, vesicle, hyphal coil and non-septate hypha, were observed in each sample. The AMF colonization rate per unit root length was calculated using the grid-crossing method [38].

2.5. Calculation of Plant Cd Accumulation, Metal Tolerance Index, Transfer Factor, and Bioconcentration Factor

Plant Cd accumulation, metal tolerance index, transfer factor, and bioconcentration factor were used to evaluate the tolerance and Cd uptake capacity of plants. These indicators were calculated as follows:
Shoot   Cd   accumulation = shoot   biomass   ×   shoot   Cd   concentration
Root   Cd   accumulation = root   biomass   ×   root   Cd   concentration
Metal   tolerance   index = plant   biomass   under   Cd   treatments plant   biomass   under   Cd   free   soil
Transfer   factor = shoot   Cd   concentration root   Cd   concentration
Bioconcentration   factor = total   Cd   concentration   in   plant total   Cd   concentration   in   soil

2.6. Statistical Analysis

The two-way ANOVA was used to examine the effects of plant species, Cd, and their interaction on the D. eburnea colonization rate. The one-way ANOVA was used to examine the effects of AMF and Cd addition on soil properties, plant biomass, Cd uptake, and heavy metal tolerance for each plant species. Duncan’s test was used to compare the means among different treatments when the homogeneity of variance was satisfied; otherwise, the data were log or square root transformed. When the variances remained unequal, Tamhane’s T2 test was used as a post hoc test for multiple comparisons. A structural equation model (SEM) was also established using AMOS 24.0 to investigate the hypothetical approach associated with the effect of D. eburnea and Cd addition on the D. eburnea colonization rate and the bioconcentration factor for each plant species. Statistical analyses were performed using SPSS version 23.0, and the significance level was set at p < 0.05.

3. Results

3.1. D. eburnea Colonization Rate

The colonization rates of D. eburnea ranged from 11.00% to 29.60% for L. perenne, and 19.13% to 64.28% for A. fruticosa (Figure 1). The two-way ANOVA showed that the D. eburnea colonization rate was significantly influenced by the plant species and Cd, but not by their interaction (Figure 1). The addition of Cd had no effect on the root colonization rate of L. perenne (Figure 1). However, when compared with the Cd-free (0 mg/kg) treatment, the root colonization rate of A. fruticosa in low-Cd (5 mg/kg) and high-Cd (15 mg/kg) soil was significantly decreased by 45.15% and 26.10%, respectively (Figure 1).

3.2. Plant Biomass

Regardless of D. eburnea inoculation, the shoot biomass of L. perenne and A. fruticosa in the high-Cd treatment was lower than that in the Cd-free treatment (Figure 2a). Furthermore, in the absence of D. eburnean, A. fruticosa shoot biomass was significantly decreased in the low-Cd treatment. However, D. eburnea inoculation had no significant effect on shoot biomass of L. perenne or A. fruticosa in any of the Cd treatments (Figure 2a).
When compared with Cd-free plants, the root biomass of L. perenne was significantly increased by 62.81% in the high-Cd treatment when D. eburnea was present, while the total biomass of L. perenne was significantly decreased by 43.13% in the high-Cd treatment in the absence of D. eburnea (Figure 2b,c). D. eburnea inoculation significantly increased the root and total biomass of L. perenne by 206.47% and 103.72%, respectively, in the high-Cd treatment (Figure 2b,c). Regardless of D. eburnea inoculation, Cd addition had no significant effect on the root and total biomass of A. fruticosa (Figure 2b,c).
Without D. eburnea inoculation, the root-to-shoot rate of L. perenne was significantly higher under the low-Cd treatment than under the control and high-Cd treatments. By contrast, with D. eburnea inoculation, the root-to-shoot rate of L. perenne was significantly higher under the high-Cd treatment than under the Cd-free or low-Cd treatments (Figure 2d). However, Cd addition had no significant effect on the root to shoot rate of A. fruticosa, regardless of D. eburnea inoculation. D. eburnea inoculation significantly decreased the root to shoot rate of L. perenne by 27.31% under the low-Cd treatment, but significantly increased the root shoot ratio of L. perenne by 145.03% under the high-Cd treatment. Moreover, the root to shoot rate of A. fruticosa was significantly increased by D. eburnea inoculation by 58.21% and 77.00% under the control and low-Cd treatments, respectively (Figure 2d).

3.3. Soil Parameters

Compared with the Cd-free treatment, the pH of L. perenne soil was significantly increased in the low-Cd treatment without D. eburnea inoculation, whereas that of A. fruticosa soil was not significantly affected by D. eburnea inoculation or Cd addition (Table 2).
When D. eburnea was not inoculated, the available phosphorus (A-P) concentration in L. perenne soil in the low-Cd treatment was significantly lower than that under Cd-free or high-Cd treatments. However, compared with the Cd-free treatment, the A-P concentration in L. perenne soil was significantly increased by 96.70% under the low-Cd treatment when D. eburnea was inoculated. The A-P concentration in A. fruticosa soil was significantly increased in the high-Cd treatment, with or without D. eburnea (Table 2).
The high-Cd treatment significantly increased the NH4+-N and NO3−-N concentrations in L. perenne soil, compared to the low-Cd treatment after D. eburnea inoculation. However, Cd addition had no significant effect on the NH4+-N or NO3−-N concentrations in A. fruticosa soil, regardless of D. eburnea inoculation. D. eburnea inoculation had no significant effect on NH4+-N concentration in L. perenne or A. fruticosa soils in any of the Cd treatments (Table 2). However, D. eburnea inoculation significantly increased the NO3−-N concentration in L. perenne and A. fruticosa soils by 66.51% and 65.80%, respectively, under the high-Cd treatment (Table 2).
Neutral phosphatase activity in L. perenne and A. fruticosa soils and alkaline phosphatase activity in L. perenne soil were not significantly affected by Cd addition or D. eburnea inoculation (Table 2). Compared with Cd-free soil, the alkaline phosphatase activity in A. fruticosa soil was significantly increased by high-Cd treatment by 21.79% in the absence of D. eburnea, while it was significantly decreased in the high-Cd treatment by 24.35% in the presence of D. eburnea (Table 2). Alkaline phosphatase activity in A. fruticosa soil was significantly increased by D. eburnea inoculation under the Cd-free treatment, but was decreased by D. eburnea inoculation under the high-Cd treatment (Table 2).

3.4. Soil Cd Fractions

Compared with the low-Cd treatment, exchangeable Cd was significantly increased and carbonate-bound Cd was significantly decreased by the high-Cd addition in soils of both plant species, whether D. eburnea was inoculated or not (Figure 3a,b). Residual Cd was significantly higher under the low-Cd treatment without D. eburnea than under the other treatments (Figure 3a,b). Under the low-Cd treatment, D. eburnea inoculation significantly increased exchangeable Cd by 3.73% in L. perenne soil and significantly decreased residual Cd by 1.56% and 3.90% in L. perenne and A. fruticosa soils, respectively (Figure 3a,b).

3.5. Plant Cd Concentration and Accumulation

The shoot Cd concentrations of both plants significantly increased with an increase in the soil Cd concentration, regardless of D. eburnea inoculation (Figure 4a). D. eburnea inoculation significantly decreased the shoot Cd concentration of L. perenne by 28.54% under the high-Cd treatment, but had no significant effect on the shoot Cd concentration of A. fruticosa in any of the Cd treatments (Figure 4a). Regardless of D. eburnea inoculation, the high-Cd treatment significantly increased the root Cd concentration of L. perenne compared with the low-Cd treatment (Figure 4b). Among all the Cd treatments, D. eburnea inoculation had no significant effect on the root Cd concentration of L. perenne. Compared with the low-Cd treatment, the high-Cd treatment significantly increased the root Cd concentration of A. fruticosa by 189.74% under the D. eburnea inoculation treatment (Figure 4b). D. eburnea inoculation significantly increased the root Cd concentration of A. fruticosa by 252.44% under the high-Cd treatment (Figure 4b).
Regardless of D. eburnea inoculation, shoot Cd accumulation in L. perenne was significantly increased by the high-Cd treatment compared to the low-Cd treatment (Figure 4c). Neither D. eburnea inoculation nor Cd addition had a significant effect on shoot Cd accumulation in A. fruticosa (Figure 4c). Compared with the low-Cd treatment, the high-Cd treatment significantly increased root Cd accumulation in L. perenne under D. eburnea inoculation (Figure 4d). D. eburnea inoculation significantly increased root Cd accumulation in L. perenne by 260.98% under the high-Cd treatment. In addition, D. eburnea inoculation significantly increased root Cd accumulation in A. fruticosa by 161.37% and 398.31% under all low- and high-Cd treatments, respectively (Figure 4d).

3.6. Metal Tolerance Index, Transfer Factor, and Bioconcentration Factor (BCF)

In the absence of D. eburnea, the metal tolerance index of L. perenne was significantly reduced in the high-Cd treatment by 50.75% compared with the low-Cd treatment, but the metal tolerance index of L. perenne was significantly increased by 19.94% in the presence of D. eburnea. However, D. eburnea inoculation significantly decreased the metal tolerance index of L. perenne by 16.36% under the low-Cd treatment, but it significantly increased the metal tolerance index of L. perenne by 103.72% under the high-Cd treatment (Figure 5a). Compared with the low-Cd treatment, the metal tolerance index of A. fruticosa inoculated with D. eburnea in the high-Cd treatment was significantly reduced by 34.61%, and D. eburnea inoculation significantly increased the metal tolerance index of A. fruticosa by 33.30% under the low-Cd treatment (Figure 5a).
Compared with the low-Cd treatment, the high-Cd treatment had no significant effect on the transfer factor of L. perenne, but it significantly increased the transfer factor of A. fruticosa by 132.60% under non-AMF D. eburnea inoculation (Figure 5b), whereas D. eburnea inoculation significantly decreased the transfer factor of A. fruticosa by 59.34% under the high-Cd treatment (Figure 5b).
Compared with the low-Cd treatment, the bioconcentration factor of A. fruticosa was significantly increased by 8.77% in the high-Cd treatment by 8.77% in the presence of D. eburnea. D. eburnea inoculation had no significant effect on the bioconcentration factor of L. perenne but significantly increased the bioconcentration factor of A. fruticosa by 47.11% and 51.88% under the low and high Cd treatments, respectively (c).

3.7. Pathways of AMF D. eburnea and Cd Treatment Effects on D. eburnea Colonization Rate and Bioconcentration Factor

A structural equation model (SEM) analysis was conducted to separately evaluate the influence of the addition of AMF D. eburnea and Cd on the AMF colonization rate and bioconcentration factor for each plant species. According to the model, AMF D. eburnea inoculation had a direct and significant positive impact on the root biomass and plant colonization rate (Figure 6a) and a direct and positive impact on the soil neutral phosphatase content, but the impact was not significant (Figure 6a). The addition of Cd indirectly reduced the colonization rate of D. eburnea by increasing the proportion of exchangeable Cd, but it had no direct or significant impact on the colonization rate of D. eburnea (Figure 6a). Furthermore, D. eburnea inoculation had a direct and significant positive impact on the root biomass of L. perenne (Figure 6b), where the addition of Cd indirectly improved the bioconcentration factor of L. perenne by increasing the proportion of exchangeable Cd in the soil (Figure 6b). AMF D. eburnea inoculation had a direct and significant positive effect on the bioconcentration factor of A. fruticose, where the addition of Cd had a direct and significant negative impact on the root biomass of A. fruticosa (Figure 6c). Moreover, the addition of Cd indirectly reduced the root biomass of A. fruticosa by increasing the soil pH value (Figure 6c).

4. Discussion

4.1. Cd in Soil Affected the Colonization Rate of AMF D. eburnea

The colonization rate of AMF D. eburnea was decreased with an increase in Cd concentration in soil, and this occurrence has already been verified in other studies [39,40]. The structural equation model proved that Cd increased the proportion of exchangeable Cd in the soil, which increased the biological toxicity of Cd in the soil and inhibited the development of D. eburnea [41]. Moreover, the AMF colonization rate of Leguminosae A. fruticosa was generally higher than that of Gramineae L. perenne. It is considered that AMF provides A. fruticosa with plenty of phosphorus in the process of nitrogen fixation [33,34], while receiving nitrogen nutrition to improve symbiosis with the host plants [42].

4.2. AMF Inoculation and Cd Addition Affected Cd Fractions in Soil

The form of Cd in the soil affects its toxicity and uptake by plants [43]. In this study, the addition of Cd significantly increased the proportion of exchangeable Cd and reduced the proportion of carbonate bound Cd. Previous studies have shown that an increase in pH reduces the number of Cd ions in soil [44]. However, when pH increases to a high level, the solubility of Cd is increased [45,46,47], and some of the Cd ions in high-pH soil form Cd hydroxide precipitation [48,49]. In the present study, the AMF treatment increased the proportion of exchangeable Cd and decreased the residual Cd in the soil. This phenomenon has also been observed in previous studies [20]. It is considered that this occurred because D. eburnea inoculation increased the plant root biomass, and the amount of plant root activated soil Cd during the plant growth process, which resulted in an increase in the proportion of exchangeable Cd [50].

4.3. AMF Impact on Plant Biomass and Cd Uptake

D. eburnea inoculation increased the total biomass and root shoot ratio of both L. perenne and A. fruticosa under the high-Cd treatment, and this may have occurred because D. eburnea improved the soil environment (e.g., NO3−-N) and promotes plant growth [15]. The results of the structural equation model showed that D. eburnea inoculation had a positive effect on the root biomass, and the increased soil neutral phosphatase content significantly increased the plant root biomass (Figure 6a). The A-P concentration in soil was decreased in this study when D. eburnea was inoculated with a high-Cd treatment. This may be that the content of available phosphorus in the soil itself was relatively low (Table 1 and Table 2), and because D. eburnea inoculation increased the root biomass and the soil neutral phosphatase content, which enabled greater amounts of A-P to be absorbed by the plants [51]. Under the high-Cd treatment, D. eburnea reduced the transfer factor by 50.08% for L. perenne and 59.34% for A. fruticosa, which showed that AMF inhibited the transport of Cd to the plant aerial parts at high-Cd concentrations, thus reducing the damage caused by Cd to aerial parts and improving the resistance of plants. This phenomenon has also been observed in other studies [52,53], and it could result from AMF changing the intracellular distribution and chemical form of Cd in the roots and it increases the cellulose in root cell walls to bind Cd ions [25,54].
Some studies have shown that AMF can promote the absorption of Cd by plants [20,55], but other studies have reported opposite results [12,56]. The mechanism underlying this difference remains unclear. However, according to the findings of our study and those of others, it is possible that different AMF species, plant species, soil properties, and Cd concentrations have different effects on the efficiency of AMF in promoting Cd uptake. The differences between the plant species in this study were mainly evident with respect to the metal tolerance of L. perenne and A. fruticosa. In this respect, L. perenne showed a high tolerance to heavy metals in low-Cd soils and a low tolerance in high-Cd soils, whereas A. fruticosa showed a low tolerance to heavy metals in all of the Cd-treated soils, and the results are consistent with those of previous studies [57]. In summary, inoculation with D. eburnea increased the biomass of plant roots, increased the Cd content of plant roots, and improved the enrichment capacity of plants.

5. Conclusions

In our study, the biomass and Cd absorption capacity of L. perenne were higher than those of A. fruticosa regardless of D. eburnea inoculation. Under the high-Cd treatment, D. eburnea increased the root biomass and root shoot ratio of both L. perenne and A. fruticosa, and it also increased the Cd absorption and bioconcentration factor of L. perenne and A. fruticosa by altering the soil Cd speciation by increasing exchangeable Cd and decreasing residual Cd. However, Cd was mainly accumulated in the plant roots. Our study indicates that the combined use of D. eburnea and remediation plants may be a viable alternative for remediating Cd-contaminated soil. However, the current data were obtained under greenhouse conditions over a two-month period, and this may not be representative of the influence of AMF in a natural environment. In addition, soil heavy metal pollution under natural conditions can involve significant heavy metal content. Therefore, it is necessary to verify whether the results obtained in this study can be extrapolated to other heavy metal pollutants.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/ijerph20010795/s1. Table S1: Composition of full-strength Hoagland nutrient solution liquid. Table S2: The effects of plant species (Plant), Cd, AMF and their interactions on shoot biomass, root biomass, total biomass, root shoot rate, pH, available phosphorus (A-P), neutral phosphatase, alkaline phosphatase, ammonium nitrogen (NH4+-N), nitrate nitrogen (NO3−-N), shoot Cd concentration, root Cd concentration, shoot Cd accumulation, root Cd accumulation, total Cd accumulation, metal tolerance index, transfer factor, and bioconcentration factor by three-way ANOVA.

Author Contributions

N.S. and S.F. conceived and designed the experiments; Y.L. and T.Z. performed the pot experiments and collected the samples; Q.J., K.D., J.C., Y.R. and S.X. assisted J.S. in completing the soil physical and chemical experiments, and J.S. analyzed the data and wrote the paper; N.S. and S.F. polished the English language to improve the quality of this manuscript. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the National Natural Science Foundation of China (No. 31800438), Key Science and Technology Research and Development & Promotion Project of Henan (No. 202102110064), and Interdisciplinary Research for First-class Discipline Construction Project of Henan University (No. 2019YLXKJC04).

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Applicable.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Haider, F.U.; Cai, L.Q.; Coulter, J.A.; Cheema, S.A.; Wu, J.; Zhang, R.Z.; Ma, W.J.; Farooq, M. Cadmium toxicity in plants: Impacts and remediation strategies. Ecotoxicol. Environ. Saf. 2021, 211, 111887. [Google Scholar] [CrossRef] [PubMed]
  2. Wei, B.; Yang, L. A review of heavy metal contaminations in urban soils, urban road dusts and agricultural soils from China. Microchem. J. 2010, 94, 99–107. [Google Scholar] [CrossRef]
  3. Zhao, F.-J.; Ma, Y.; Zhu, Y.-G.; Tang, Z.; McGrath, S.P. Soil Contamination in China: Current Status and Mitigation Strategies. Environ. Sci. Technol. 2015, 49, 750–759. [Google Scholar] [CrossRef] [PubMed]
  4. Yan, L.J.; Allen, D.C. Cadmium-Induced Kidney Injury: Oxidative Damage as a Unifying Mechanism. Biomolecules 2021, 11, 1575. [Google Scholar] [CrossRef] [PubMed]
  5. Jarup, L. Hazards of heavy metal contamination. Br. Med. Bull. 2003, 68, 167–182. [Google Scholar] [CrossRef] [Green Version]
  6. Uraguchi, S.; Fujiwara, T. Cadmium transport and tolerance in rice: Perspectives for reducing grain cadmium accumulation. Rice 2012, 5, 5. [Google Scholar] [CrossRef] [Green Version]
  7. Bolan, N.; Kunhikrishnan, A.; Thangarajan, R.; Kumpiene, J.; Park, J.; Makino, T.; Kirkham, M.B.; Scheckel, K. Remediation of heavy metal(loid)s contaminated soils—To mobilize or to immobilize? J. Hazard. Mater. 2014, 266, 141–166. [Google Scholar] [CrossRef]
  8. Cameselle, C.; Gouveia, S.; Urrejola, S. Benefits of phytoremediation amended with DC electric field. Application to soils contaminated with heavy metals. Chemosphere 2019, 229, 481–488. [Google Scholar] [CrossRef]
  9. Ullah, A.; Heng, S.; Munis, M.F.H.; Fahad, S.; Yang, X. Phytoremediation of heavy metals assisted by plant growth promoting (PGP) bacteria: A review. Environ. Exp. Bot. 2015, 117, 28–40. [Google Scholar] [CrossRef]
  10. Gavrilescu, M. Enhancing phytoremediation of soils polluted with heavy metals. Curr. Opin. Biotechnol. 2022, 74, 21–31. [Google Scholar] [CrossRef]
  11. Van der Heijden, M.G.A.; Boller, T. Different arbuscular mycorrhizal fungal species are potential determinants of plant community. Ecology 1998, 79, 2082. [Google Scholar] [CrossRef]
  12. Aalipour, H.; Nikbakht, A.; Etemadi, N. Physiological response of Arizona cypress to Cd-contaminated soil inoculated with arbuscular mycorrhizal fungi and plant growth promoting rhizobacteria. Rhizosphere 2021, 18, 100354. [Google Scholar] [CrossRef]
  13. Bisht, A.; Garg, N. AMF species improve yielding potential of Cd stressed pigeonpea plants by modulating sucrose-starch metabolism, nutrients acquisition and soil microbial enzymatic activities. Plant Growth Regul. 2022, 96, 409–430. [Google Scholar] [CrossRef]
  14. De Andrade, S.A.L.; da Silveira, A.P.D.; Jorge, R.A.; de Abreu, M.F. Cadmium accumulation in sunflower plants influenced by arbuscular mycorrhiza. Int. J. Phytoremediat. 2008, 10, 1–13. [Google Scholar] [CrossRef] [PubMed]
  15. Li, J.; Benti, G.; Wang, D.; Yang, Z.; Xiao, R. Effect of Alteration in Precipitation Amount on Soil Microbial Community in a Semi-Arid Grassland. Front. Microbiol. 2022, 13, 842446. [Google Scholar] [CrossRef]
  16. Li, J.; Charles, L.S.; Yang, Z.; Du, G.; Fu, S. Differential Mechanisms Drive Species Loss Under Artificial Shade and Fertilization in the Alpine Meadow of the Tibetan Plateau. Front. Plant Sci. 2022, 13, 832473. [Google Scholar] [CrossRef]
  17. Li, S.Q.; Li, G.D.; Peng, K.M.; Yang, L.H.; Huang, X.F.; Lu, L.J.; Liu, J. The combined effect of Diversispora versiformis and sodium bentonite contributes on the colonization of Phragmites in cadmium-contaminated soil. Chemosphere 2022, 293, 133613. [Google Scholar] [CrossRef]
  18. Mollavali, M.; Bolandnazar, S.A.; Schwarz, D.; Rohn, S.; Riehle, P.; Nahandi, F.Z. Flavonol glucoside and antioxidant enzyme biosynthesis affected by mycorrhizal fungi in various cultivars of onion (Allium cepa L.). J. Agric. Food Chem. 2015, 64, 71–77. [Google Scholar]
  19. Wang, G.; Wang, L.; Ma, F.; Yang, D.; You, Y. Earthworm and arbuscular mycorrhiza interactions: Strategies to motivate antioxidant responses and improve soil functionality. Environ. Pollut. 2020, 272, 115980. [Google Scholar] [CrossRef]
  20. Wang, G.; Wang, L.; Ma, F.; You, Y.; Wang, Y.; Yang, D. Integration of earthworms and arbuscular mycorrhizal fungi into phytoremediation of cadmium-contaminated soil by Solanum nigrum L. J. Hazard. Mater. 2020, 389, 121873. [Google Scholar] [CrossRef]
  21. Hassan, S.E.; Hijri, M.; St-Arnaud, M. Effect of arbuscular mycorrhizal fungi on trace metal uptake by sunflower plants grown on cadmium contaminated soil. New Biotechnol. 2013, 30, 780–787. [Google Scholar] [CrossRef]
  22. Jiang, Y.; Huang, R.; Jiang, L.; Chen, K.; Zhu, W. Alleviation of Cadmium Toxicity to Medicago Truncatula by AMF Involves the Changes of Cd Speciation in Rhizosphere Soil and Subcellular Distribution. Phyton-Int. J. Exp. Bot. 2021, 90, 403–415. [Google Scholar] [CrossRef]
  23. Li, H.; Luo, N.; Zhang, L.J.; Zhao, H.M.; Li, Y.W.; Cai, Q.Y.; Wong, M.H.; Mo, C.H. Do arbuscular mycorrhizal fungi affect cadmium uptake kinetics, subcellular distribution and chemical forms in rice? Sci. Total Environ. 2016, 571, 1183–1190. [Google Scholar] [CrossRef] [PubMed]
  24. Huang, X.; Wang, L.; Zhu, S.; Ho, S.-H.; Wu, J.; Kalita, P.K.; Ma, F. Unraveling the effects of arbuscular mycorrhizal fungus on uptake, translocation, and distribution of cadmium in Phragmites australis (Cav.) Trin. ex Steud. Ecotoxicol. Environ. Saf. 2018, 149, 43–50. [Google Scholar] [CrossRef] [PubMed]
  25. Buck, M.T.; Straker, C.J.; Mavri-Damelin, D.; Weiersbye, I.M. Diversity of arbuscular mycorrhizal (AM) fungi colonising roots of indigenous Vachellia and Senegalia trees on gold and uranium mine tailings in South Africa. S. Afr. J. Bot. 2019, 121, 34–44. [Google Scholar] [CrossRef]
  26. Alguacil, M.M.; Torrecillas, E.; Caravaca, F.; Fernández, D.; Azcón, R.; Roldán, A. The application of an organic amendment modifies the arbuscular mycorrhizal fungal communities colonizing native seedlings grown in a heavy-metal-polluted soil. Soil Biol. Biochem. 2011, 43, 1498–1508. [Google Scholar] [CrossRef]
  27. Sikdar, A.; Wang, J.; Hasanuzzaman, M.; Liu, X.; Feng, S.; Roy, R.; Sial, T.A.; Lahori, A.H.; Arockiam Jeyasundar, P.G.S.; Wang, X. Phytostabilization of Pb-Zn Mine Tailings with Amorpha fruticosa Aided by Organic Amendments and Triple Superphosphate. Molecules 2020, 25, 1617. [Google Scholar] [CrossRef] [Green Version]
  28. Bahmani-Babanari, L.; Mirzahosseini, Z.; Shabani, L.; Sabzalian, M.R. Effect of arbuscular mycorrhizal fungus, Funneliformis fasciculatum, on detoxification of Nickel and expression of TIP genes in Lolium perenne L. Biologia 2021, 76, 1675–1683. [Google Scholar] [CrossRef]
  29. Malicka, M.S.; Magurno, F.; Posta, K.; Chmura, D.; Piotrowska-Seget, Z. Differences in the effects of single and mixed AMF species on the growth and oxidative stress defense in Lolium perenne exposed to hydrocarbons. Ecotoxicol. Environ. Saf. 2021, 217, 112252. [Google Scholar] [CrossRef]
  30. Bi, Y.; Guo, Y.; Christie, P. Mining subsidence area reconstruction with N2-fixing plants promotes arbuscular mycorrhizal fungal biodiversity and microbial biomass C:N:P stoichiometry of cyanobacterial biocrusts. For. Ecol. Manag. 2022, 503, 119763. [Google Scholar] [CrossRef]
  31. Song, F.Q.; Qi, D.D.; Liu, X.; Kong, X.S.; Gao, Y.; Zhou, Z.X.; Wu, Q. Proteomic analysis of symbiotic proteins of Glomus mosseae and Amorpha fruticosa. Sci. Rep. 2015, 5, 18031. [Google Scholar] [CrossRef]
  32. Detheridge, A.P.; Brand, G.; Fychan, R.; Crotty, F.V.; Sanderson, R.; Griffith, G.W.; Marley, C.L. The legacy effect of cover crops on soil fungal populations in a cereal rotation. Agric. Ecosyst. Environ. 2016, 228, 49–61. [Google Scholar] [CrossRef] [Green Version]
  33. Redecker, D.; Berswordt-Wallrabe, P.V.; Beck, D.P.; Werner, D. Influence of inoculation with arbuscular mycorrhizal fungi on stable isotopes of nitrogen in Phaseolus vulgaris. Biol. Fert. Soils. 1997, 24, 344–346. [Google Scholar] [CrossRef]
  34. Zhao, B.; Trouvelot, A.; Gianinazzi, S.; Gianinazzi-Pearson, V. Influence of two legume species on hyphal production and activity of two arbuscular mycorrhizal fungi. Mycorrhiza 1997, 7, 179–185. [Google Scholar] [CrossRef]
  35. Hoagland, D.R.; Arnon, D.I. The water culture method for growing plants without soil. Calif. Agric. Exp. Stn. Circ. 1950, 347, 32. [Google Scholar]
  36. Tessier, A.P.; Campbell, P.G.C.; Bisson, M.X. Sequential extraction procedure for the speciation of particulate trace metals. Anal. Chem. 1979, 51, 844–851. [Google Scholar] [CrossRef]
  37. Kormanik, P.P.; Bryan, W.C.; Schultz, R.C. Procedures and equipment for staining large numbers of plant root samples for endomycorrhizal assay. Can. J. Microbiol. 1980, 26, 536–538. [Google Scholar] [CrossRef]
  38. McGonigle, T.P.; Miller, M.H.; Evans, D.G.; Fairchild, G.L.; Swan, J.A. A new method which gives an objective measure of colonization of roots by vesicular-arbuscular mycorrhizal fungi. New Phytol. 1990, 115, 495–501. [Google Scholar] [CrossRef]
  39. Rafique, M.; Ortas, I.; Rizwan, M.; Sultan, T.; Chaudhary, H.J.; Isik, M.; Aydin, O. Effects of Rhizophagus clarus and biochar on growth, photosynthesis, nutrients, and cadmium (Cd) concentration of maize (Zea mays) grown in Cd-spiked soil. Environ. Sci. Pollut. Res. 2019, 26, 20689–20700. [Google Scholar] [CrossRef]
  40. Gai, J.P.; Fan, J.Q.; Zhang, S.B.; Mi, N.N.; Christie, P.; Li, X.L.; Feng, G. Direct effects of soil cadmium on the growth and activity of arbuscular mycorrhizal fungi. Rhizosphere 2018, 7, 43–48. [Google Scholar] [CrossRef]
  41. Del Val, C.; Barea, J.M.; Azcon-Aguilar, C. Diversity of arbuscular mycorrhizal fungus populations in heavy-metal-contaminated soils. Appl. Environ. Microbiol. 1999, 65, 718–723. [Google Scholar] [CrossRef] [Green Version]
  42. Dandan, Z.; Tao, L.I.; Zhiwei, Z. Research advances in arbuscular mycorrhizal fungi-legumes-rhizobia symbiosis. Chin. J. Ecol. 2006, 25, 327–333. [Google Scholar]
  43. Chen, Z.; Ai, Y.; Fang, C.; Wang, K.; Li, W.; Liu, S.; Li, C.; Xiao, J.; Huang, Z. Distribution and phytoavailability of heavy metal chemical fractions in artificial soil on rock cut slopes alongside railways. J. Hazard. Mater. 2014, 273, 165–173. [Google Scholar] [CrossRef] [PubMed]
  44. Zhan, F.; Li, B.; Jiang, M.; Li, T.; He, Y.; Li, Y.; Wang, Y. Effects of arbuscular mycorrhizal fungi on the growth and heavy metal accumulation of bermudagrass [Cynodon dactylon (L.) Pers.] grown in a lead–zinc mine wasteland. Int. J. Phytoremediat. 2019, 21, 849–856. [Google Scholar] [CrossRef] [PubMed]
  45. McBride, M.B.; Martinez, C.E. Copper phytotoxicity in a contaminated soil: Remediation tests with adsorptive materials. Environ. Sci. Technol. 2000, 34, 4386–4391. [Google Scholar] [CrossRef]
  46. Wang, M.; Liu, Y.B.; Shi, H.D.; Li, S.N.; Chen, S.B. Yielding hydroxyl radicals in the Fenton-like reaction induced by manganese (II) oxidation determines Cd mobilization upon soil aeration in paddy soil systems. Environ. Pollut. 2022, 292, 118311. [Google Scholar] [CrossRef]
  47. Stec, M.; Jagustyn, B.; Slowik, K.; Sciazko, M.; Iluk, T. Influence of High Chloride Concentration on pH Control in Hydroxide Precipitation of Heavy Metals. J. Sustain. Metall. 2020, 6, 239–249. [Google Scholar] [CrossRef] [Green Version]
  48. Zhang, H.Q.; Wang, Z.X.; Du, C.Y.; Liu, W.L.; Gerson, A.R.; Pi, K.W. Properties and heavy metal leaching characteristics of leachate sludge-derived biochar. Water Environ. Res. 2021, 93, 3064–3074. [Google Scholar] [CrossRef]
  49. Mortimer, R.J.G.; Rae, J.E. Metal speciation (Cu, Zn, Pb, Cd) and organic matter in oxic to suboxic salt marsh sediments, Severn Estuary, southwest Britain. Mar. Pollut. Bull. 2000, 40, 377–386. [Google Scholar] [CrossRef]
  50. Wahid, F.; Fahad, S.; Danish, S.; Adnan, M.; Yue, Z.; Saud, S.; Siddiqui, M.H.; Brtnicky, M.; Hammerschmiedt, T.; Datta, R. Sustainable Management with Mycorrhizae and Phosphate Solubilizing Bacteria for Enhanced Phosphorus Uptake in Calcareous Soils. Agriculture 2020, 10, 334. [Google Scholar] [CrossRef]
  51. Treseder, K.K.; Allen, E.B.; Egerton-Warburton, L.M.; Hart, M.M.; Klironomos, J.N.; Maherali, H.; Tedersoo, L. Arbuscular mycorrhizal fungi as mediators of ecosystem responses to nitrogen deposition: A trait-based predictive framework. J. Ecol. 2018, 106, 480–489. [Google Scholar] [CrossRef] [Green Version]
  52. He, Y.M.; Fan, X.M.; Zhang, G.Q.; Li, B.; Li, T.G.; Zu, Y.Q.; Zhan, F.D. Effects of arbuscular mycorrhizal fungi and dark septate endophytes on maize performance and root traits under a high cadmium stress. S. Afr. J. Bot. 2020, 134, 415–423. [Google Scholar] [CrossRef]
  53. Zhan, F.; Li, B.; Jiang, M.; Yue, X.; He, Y.; Xia, Y.; Wang, Y. Arbuscular mycorrhizal fungi enhance antioxidant defense in the leaves and the retention of heavy metals in the roots of maize. Environ. Sci. Pollut. Res. 2018, 25, 24338–24347. [Google Scholar] [CrossRef] [PubMed]
  54. Chen, X.W.; Kang, Y.; So, P.S.; Ng, C.W.W.; Wong, M.H. Arbuscular mycorrhizal fungi increase the proportion of cellulose and hemicellulose in the root stele of vetiver grass. Plant Soil 2018, 425, 309–319. [Google Scholar] [CrossRef]
  55. Rasouli-Sadaghiani, M.H.; Barin, M.; Khodaverdiloo, H.; Moghaddam, S.S.; Damalas, C.A.; Kazemalilou, S. Arbuscular Mycorrhizal Fungi and Rhizobacteria Promote Growth of Russian Knapweed (Acroptilon repens L.) in a Cd-Contaminated Soil. J. Plant Growth Regul. 2019, 38, 113–121. [Google Scholar] [CrossRef]
  56. Baghaie, A.H.; Aghili, F.; Jafarinia, R. Soil-indigenous arbuscular mycorrhizal fungi and zeolite addition to soil synergistically increase grain yield and reduce cadmium uptake of bread wheat (through improved nitrogen and phosphorus nutrition and immobilization of Cd in roots). Environ. Sci. Pollut. Res. 2019, 26, 30794–30807. [Google Scholar] [CrossRef]
  57. He, S.; Wu, Q.; He, Z. Growth-Promoting Hormone DA-6 Assists Phytoextraction and Detoxification of Cd by Ryegrass. Int. J. Phytoremediat. 2015, 17, 597–603. [Google Scholar] [CrossRef]
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Figure 1. AMF colonization rate (Means ± SE, n = 4) of L. perenne and A. fruticosa under different Cd concentrations. Different letters indicate significant differences among treatments for each plant species according to Duncan’s test at p < 0.05. 0, no Cd added to soil; 5, 5 mg/kg Cd added to soil; 15, 15 mg/kg Cd added to soil. ***, p < 0.001; ns, not significant.
Figure 1. AMF colonization rate (Means ± SE, n = 4) of L. perenne and A. fruticosa under different Cd concentrations. Different letters indicate significant differences among treatments for each plant species according to Duncan’s test at p < 0.05. 0, no Cd added to soil; 5, 5 mg/kg Cd added to soil; 15, 15 mg/kg Cd added to soil. ***, p < 0.001; ns, not significant.
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Figure 2. Effects of AMF and Cd addition on shoot biomass (a), root biomass (b), total biomass (c), and root to shoot rate (d) of L. perenne and A. fruticosa (Means ± SE, n = 4). Different letters indicate significant differences among treatments for each plant species according to Duncan’s or Tamhane’s T2 test at p < 0.05. −AMF, not inoculated with D. eburnea; +AMF, inoculated with D. eburnea; 0, no Cd added to soil; 5, 5 mg/kg Cd added to soil; 15, 15 mg/kg Cd added to soil.
Figure 2. Effects of AMF and Cd addition on shoot biomass (a), root biomass (b), total biomass (c), and root to shoot rate (d) of L. perenne and A. fruticosa (Means ± SE, n = 4). Different letters indicate significant differences among treatments for each plant species according to Duncan’s or Tamhane’s T2 test at p < 0.05. −AMF, not inoculated with D. eburnea; +AMF, inoculated with D. eburnea; 0, no Cd added to soil; 5, 5 mg/kg Cd added to soil; 15, 15 mg/kg Cd added to soil.
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Figure 3. Percentage of different soil Cd forms under different treatments for L. perenne (a) and A. fruticosa (b) (means ± SE, n = 4). Different letters indicate significant differences among treatments for each plant species according to Duncan’s test or Tamhane’s T2 post hoc test at p < 0.05. 5 mg/kg, 5 mg/kg Cd added to soil; 5 mg/kg + AMF, 5 mg/kg cadmium, and D. eburnea added to soil; 15 mg/kg, 15 mg/kg Cd added to soil; 15 mg/kg + AMF, 15 mg/kg cadmium, and D. eburnea added to soil.
Figure 3. Percentage of different soil Cd forms under different treatments for L. perenne (a) and A. fruticosa (b) (means ± SE, n = 4). Different letters indicate significant differences among treatments for each plant species according to Duncan’s test or Tamhane’s T2 post hoc test at p < 0.05. 5 mg/kg, 5 mg/kg Cd added to soil; 5 mg/kg + AMF, 5 mg/kg cadmium, and D. eburnea added to soil; 15 mg/kg, 15 mg/kg Cd added to soil; 15 mg/kg + AMF, 15 mg/kg cadmium, and D. eburnea added to soil.
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Figure 4. Effects of D. eburnea and Cd addition on shoot Cd concentration (a), root Cd concentration (b), shoot Cd accumulation (c), and root Cd accumulation (d) of L. perenne and A. fruticosa (Means ± SE, n = 4). Different letters indicate significant differences among treatments for each plant species according to Duncan’s test or Tamhane’s T2 post hoc test at p < 0.05. −AMF, not inoculated with D. eburnea; +AMF, inoculated with D. eburnea; 5, 5 mg/kg Cd added to soil; 15, 15 mg/kg Cd added to soil.
Figure 4. Effects of D. eburnea and Cd addition on shoot Cd concentration (a), root Cd concentration (b), shoot Cd accumulation (c), and root Cd accumulation (d) of L. perenne and A. fruticosa (Means ± SE, n = 4). Different letters indicate significant differences among treatments for each plant species according to Duncan’s test or Tamhane’s T2 post hoc test at p < 0.05. −AMF, not inoculated with D. eburnea; +AMF, inoculated with D. eburnea; 5, 5 mg/kg Cd added to soil; 15, 15 mg/kg Cd added to soil.
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Figure 5. Effects of D. eburnea and Cd concentration on the metal tolerance index (a), transfer factor (b), and bioconcentration factor (c) of L. perenne and A. fruticosa (Means ± SE, n = 4). Different letters indicate significant differences among treatments for each plant species according to Duncan’s test or Tamhane’s T2 post hoc test at p < 0.05. −AMF, not inoculated D. eburnea; +AMF, inoculated D. eburnea; 5, 5 mg/kg Cd added to soil; 15, 15 mg/kg Cd added to soil.
Figure 5. Effects of D. eburnea and Cd concentration on the metal tolerance index (a), transfer factor (b), and bioconcentration factor (c) of L. perenne and A. fruticosa (Means ± SE, n = 4). Different letters indicate significant differences among treatments for each plant species according to Duncan’s test or Tamhane’s T2 post hoc test at p < 0.05. −AMF, not inoculated D. eburnea; +AMF, inoculated D. eburnea; 5, 5 mg/kg Cd added to soil; 15, 15 mg/kg Cd added to soil.
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Figure 6. Structural equation model of the effects of AMF D. eburnea and Cd addition on the D. eburnea colonization rate (a), BCF of L. perenne (b) and A. fruticosa (c). The solid line indicates a significant correlation, while the dotted line indicates an insignificant correlation. The black and red arrows represent positive and negative effects, respectively. Values associated with the arrows and the arrow width represent standardized path coefficients. S-NP, soil neutral phosphatase, total biomass; ECd, exchangeable Cd; BCF, bioconcentration factor. *, p < 0.05; **, p < 0.01; ***, p < 0.001.
Figure 6. Structural equation model of the effects of AMF D. eburnea and Cd addition on the D. eburnea colonization rate (a), BCF of L. perenne (b) and A. fruticosa (c). The solid line indicates a significant correlation, while the dotted line indicates an insignificant correlation. The black and red arrows represent positive and negative effects, respectively. Values associated with the arrows and the arrow width represent standardized path coefficients. S-NP, soil neutral phosphatase, total biomass; ECd, exchangeable Cd; BCF, bioconcentration factor. *, p < 0.05; **, p < 0.01; ***, p < 0.001.
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Table
Table 1. Initial parameters of the soil and sand used for the pot experiment (means ± SE, n = 3). MBC, microbial biomass carbon; MBN, microbial biomass nitrogen; A-P, available phosphorus.
Table 1. Initial parameters of the soil and sand used for the pot experiment (means ± SE, n = 3). MBC, microbial biomass carbon; MBN, microbial biomass nitrogen; A-P, available phosphorus.
ParametersSoil PropertiesSand Properties
pH8.43 ± 0.018.30 ± 0.01
MBC (mg/kg)18.39 ± 0.0919.26 ± 0.87
MBN (mg/kg)3.61 ± 0.082.01 ± 0.07
A-P (mg/kg)0.89 ± 0.041.51 ± 0.11
NH4+-N (mg/kg)19.69 ± 0.5712.15 ± 0.34
NO3−-N (mg/kg)5.94 ± 0.143.67 ± 0.08
SOC (g/kg)13.6 ± 0.054.01 ± 0.06
TC (g/kg)15.10 ± 0.4113.43 ± 0.24
TN (g/kg)1.10 ± 0.203.98 ± 0.01
Total Cd (mg/kg)0.87 ± 0.010.35 ± 0.01
Table
Table 2. Effects of arbuscular mycorrhizal fungi and Cd on soil properties.
Table 2. Effects of arbuscular mycorrhizal fungi and Cd on soil properties.
TreatmentCKAMFCd5Cd5 + AMFCd15Cd15 + AMF
L. perennepH9.44 ± 0.02 b9.54 ± 0.05 ab9.59 ± 0.02 a9.54 ± 0.07 ab9.51 ± 0.02 ab9.49 ± 0.02 ab
Available phosphorus (mg/kg)8.07 ± 0.9 a2.88 ± 0.5 c1.47 ± 0.18 c5.66 ± 1.4 ab5.64 ± 0.9 ab3.75 ± 0.77 bc
NH4+-N (mg/kg)25.45 ± 2.62 ab23.82 ± 1.04 b24.45 ± 2.22 ab27.22 ± 1.63 ab25.95 ± 2.11 ab30.21 ± 1.46 a
NO3−-N (mg/kg)0.44 ± 0.14 b0.79 ± 0.05 b0.72 ± 0.12 b0.99 ± 0.24 b0.91 ± 0.12 b1.52 ± 0.26 a
Neutral phosphatase (U/g)0.1 ± 0.01 a0.11 ± 0.01 a0.1 ± 0.0042 a0.08 ± 0.01 a0.08 ± 0.01 a0.08 ± 0.01 a
Alkaline phosphatase (U/g)0.15 ± 0.01 a0.16 ± 0.01 a0.14 ± 0.01 a0.15 ± 0.01 a0.15 ± 0.01 a0.15 ± 0.01 a
A. fruticosapH9.23 ± 0.08 a9.3 ± 0.04 a9.42 ± 0.02 a9.43 ± 0.04 a9.37 ± 0.02 a9.48 ± 0.04 a
Available phosphorus (mg/kg)1.5 ± 0.15 b2.11 ± 0.18 b1.98 ± 0.57 b2.16 ± 0.27 b6.46 ± 0.51 a5.96 ± 0.67 a
NH4+-N (mg/kg)29.35 ± 2.85 a30.08 ± 0.65 a31.88 ± 1.32 a31.7 ± 2.09 a29.82 ± 1.06 a37.53 ± 4.58 a
NO3−-N (mg/kg)4.3 ± 0.52 ab6.51 ± 0.61 a1.74 ± 0.47 b5.13 ± 0.8 ab1.73 ± 0.17 b2.87 ± 0.52 ab
Neutral phosphatase (U/g)0.06 ± 0.001 a0.06 ± 0.0029 a0.07 ± 0.01 a0.07 ± 0.01 a0.07 ± 0.01 a0.06 ± 0.0018 a
Alkaline phosphatase (U/g)0.14 ± 0.01 b0.18 ± 0.01 a0.16 ± 0.01 ab0.15 ± 0.01 ab0.17 ± 0.01 a0.14 ± 0.01 b
Data represent the mean of four replicates ± SE. Different letters in each row indicate significant differences among treatments for each plant species according to Duncan’s test or Tamhane’s T2 post-hoc test at p < 0.05. CK, control; AMF, D. eburnea added to soil; Cd5, 5 mg/kg cadmium added to soil; Cd5 + AMF, 5 mg/kg cadmium, and D. eburnea added to soil; Cd15, 15 mg/kg cadmium added to soil; Cd15 + AMF, 15 mg/kg cadmium and D. eburnea added to soil.
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Sun, J.; Jia, Q.; Li, Y.; Dong, K.; Xu, S.; Ren, Y.; Zhang, T.; Chen, J.; Shi, N.; Fu, S. Effect of Arbuscular Mycorrhiza Fungus Diversispora eburnea Inoculation on Lolium perenne and Amorpha fruticosa Growth, Cadmium Uptake, and Soil Cadmium Speciation in Cadmium-Contaminated Soil. Int. J. Environ. Res. Public Health 2023, 20, 795. https://doi.org/10.3390/ijerph20010795

AMA Style

Sun J, Jia Q, Li Y, Dong K, Xu S, Ren Y, Zhang T, Chen J, Shi N, Fu S. Effect of Arbuscular Mycorrhiza Fungus Diversispora eburnea Inoculation on Lolium perenne and Amorpha fruticosa Growth, Cadmium Uptake, and Soil Cadmium Speciation in Cadmium-Contaminated Soil. International Journal of Environmental Research and Public Health. 2023; 20(1):795. https://doi.org/10.3390/ijerph20010795

Chicago/Turabian Style

Sun, Jiahua, Qiong Jia, Yi Li, Kanglong Dong, Shuai Xu, Yanan Ren, Ting Zhang, Jiayuan Chen, Nannan Shi, and Shenglei Fu. 2023. "Effect of Arbuscular Mycorrhiza Fungus Diversispora eburnea Inoculation on Lolium perenne and Amorpha fruticosa Growth, Cadmium Uptake, and Soil Cadmium Speciation in Cadmium-Contaminated Soil" International Journal of Environmental Research and Public Health 20, no. 1: 795. https://doi.org/10.3390/ijerph20010795

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