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Heavy metal (HM) pollution and the need to preserve the environment have gathered increasing scientific attention. The immobilization of HMs into less-soluble, less mobile, and less toxic forms in addition to the improvement of Medicago sativa L. growth and HMs accumulation were evaluated after the application of marble waste (MW) and/or beneficial PGP rhizobacteria and mycorrhizae to the mining soil compost. A greenhouse assay was conducted to elucidate the influence of both amendment and beneficial microorganisms. The application of marble waste to the soil-compost resulted in decreasing the bioavailability of metals (Cu, Zn, Pb, and Cd), thus ameliorating the installation of the vegetal cover for 6 months of culture. Cultivation of M. sativa under 5% MW-amended soil for 6 months increased the shoot dry weight by almost twofold, while the inoculation with rhizobacteria-mycorrhizae combined with the application of 15% MW resulted in an improvement of 3.5-fold in case of shoot dry weight. In addition, the application of marble waste amendment or their combination with metallo-resistant bacteria resulted in decreasing HM accumulation leading to HM content below the threshold recommended for animal grazing. Thus, the application of amendments and beneficial microorganisms appeared to guarantee the safe cultivation of alfalfa for 6 months of culture. The dual combination amendments and beneficial microorganisms showed the good potential to restore HM polluted soils and could stand as a novel approach for restoration of HM-contaminated soils., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Native arbuscular mycorrhizal fungi (AMF) generally provide more effective assistance for phytoremediation to remove heavy metal (HM) from polluted soils than non-native AMF. Nevertheless, it is a time-consuming work to isolate, identify, and propagate AMF inoculum for practical application. This study aims to explore an alternative method to improve the phytoremediation efficiency of Bidens parviflora using domesticated AMF under HM stress condition for a certain period of time. Our results showed that Funneliformis mosseae inoculation alleviated oxidative damage to plant membranes by enhancing activities of superoxide dismutase, catalase, ascorbate peroxidase, and glutathione reductase. Furthermore, mycorrhizal plants had higher chlorophyll concentration, photosynthesis efficiency, and root Pb content to protect the aerial parts from damage. These protective mechanisms were found to be more efficient in domesticated AMF inoculation compared with non-domesticated AMF inoculation. Overall, this study suggests that F. mosseae domesticated for 12 months could greatly enhance plant root Pb accumulation and plant growth mainly through strengthening antioxidant defenses as well as the photosynthesis efficiency under Pb stress conditions. Plants inoculated with pre-domesticated AMF provided a promising new strategy to enhance phytoremediation of Pb-contaminated soils., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

The application of biochar-based fertilizer can improve soil properties in part by stimulating microbial activity and growth. Karst ecosystems, which make up large areas of Southwest China, are prone to degradation. Understanding the response of arbuscular mycorrhizal fungal (AMF) community structure to biochar-based fertilizer application is of great significance to karst soil restoration. A field experiment was conducted in a typical karst soil (calcareous sandy loam) in Southwest China. A high-throughput sequencing approach was used to investigate the effect of biochar-based fertilization on AMF community structure in the karst soil. With the control (CK), compost with NPK fertilizer (MF), biochar (B), a lower amount of biochar with compost and NPK fertilizer (B1MF), biochar with compost and NPK fertilizer (BMF), and a higher amount of biochar with compost and NPK fertilizer (B4MF), the field trials were set up for 24 months. Soil amendments increased soil nutrient content and AMF diversity. The composition and structure of the AMF community varied among the treatments. AMF community composition was significantly impacted by soil chemical properties such as TC (total carbon), TN (total nitrogen), TP (total phosphorus), and AP (available phosphorus). Furthermore, network analysis showed that biochar-based fertilization increased the scale and complexity of the microbial co-occurrence network. Biochar-based fertilization enabled more keystone species (such as order Diversisporales and Glomerales) in the soil AMF network to participate in soil carbon resource management and soil nutrient cycling, indicating that biochar-based fertilizer is beneficial for the restoration of degraded karst soils., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

The use of citric acid (CA) chelator to facilitate metal bioavailability is a promising approach for the phytoextraction of heavy metal contaminants. However, the role of the CA chelator associated with arbuscular mycorrhizal fungi (AMF) inoculation on phytoextraction of vanadium (V) has not been studied. Therefore, in this study, a greenhouse pot experiment was conducted to evaluate the combined effect of CA chelator and AMF inoculation on growth performance and V phytoextraction of plants in V-contaminated soil. The experiment was performed via CA (at 0, 5, and 10 mM kg -1 soil levels) application alone or in combination with AMF inoculation by Medicago sativa Linn. (M. sativa). Plant biomass, root mycorrhizal colonization, P and V accumulation, antioxidant enzyme activity in plants, and soil chemical speciation of V were evaluated. Results depicted (1) a marked decline in plant biomass and root mycorrhizal colonization in 5- and 10-mM CA treatments which were accompanied by a significant increased V accumulation in plant tissues. The effects could be attributed to the enhanced acid-soluble V fraction transferring from the reducible fraction. (2) The presence of CA significantly enhanced P acquisition while the P/V concentration ratio in plant shoots and roots decreased, owing to the increased V translocation from soil to plant. (3) In both CA-treated soil, AMF-plant symbiosis significantly improved dry weight (31.4-73.3%) and P content (37.3-122.5%) in shoots and roots of M. sativa. The combined treatments also showed markedly contribution in reduction of malondialdehyde (MDA) content (12.8-16.2%) and higher antioxidants (SOD, POD, and CAT) activities in the leaves. This suggests their combination could promote growth performance and stimulate antioxidant response to alleviate V stress induced by CA chelator. (4) Taken together, 10 mM kg -1 CA application and AMF inoculation combination exhibited a higher amount of extracted V both in plant shoots and roots. Thus, citric acid-AMF-plant symbiosis provides a novel remediation strategy for in situ V phytoextraction by M. sativa in V-contaminated soil., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

As soil contamination with heavy metals is increasing and polyamines have roles in the growth of mycorrhiza and plants, it is important to study phytoremediation, growth, tolerance, and mycorrhization in Lallemantia iberica as a multi-purpose plant, by the application of putrescine along with mycorrhiza in Pb-contaminated soils. For this purpose, the study was performed in a factorial arrangement with Pb (0, 300, 600, and 900 mg Pb/kg soil), mycorrhiza (non-inoculation, Funneliformis mosseae (Fm), and Rhizophagus intraradices (Ri)), and putrescine (0, 0.5, and 1 mM) in a greenhouse. Results showed that antioxidant activities, plant Pb, and mycorrhizal features enhanced, while transfer factor (TF), biomass, and tolerance decreased under Pb levels. Mycorrhiza improved growth, greenness, defense, and tolerance and reduced TF, Pb, and H 2 O 2 content under Pb stress. Putrescine (0.5 mM) increased catalase activity, biomass, and colonization and reduced Pb content and TF under Pb levels. Combination of 0.5 mM putrescine with Fm increased shoot biomass (13%), peroxidase (17.2%), root P (7.5%), shoot tolerance (14.4%), colonization (5.1%), and hyphal width (5.5%) and decreased malondialdehyde (20.5%) and shoot Pb content (28.1%). Putrescine (1 mM) had negative effects on all traits in combination with Ri but not with Fm. Combination of putrescine and Fm showed more efficiency in decreasing Pb content in L. iberica and was effective in phytostabilization. It is generally concluded that 0.5 mM putrescine was the beneficial concentration in combination with mycorrhiza, Pb stress, and single use to improve plant performance, and Fm was a useful species for improving the growth and tolerance of L. iberica under Pb levels., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Glomalin is a specific glycoprotein compound synthesized by glomeral fungi and its amount varies according to soil conditions. Due to the symbiosis of these fungi with a multitude of plants, a remarkable amount of glomalin is produced inside the hypha wall of these fungi. Furthermore, while increasing the symbiosis stability, glomalin plays a critical role in reducing the availability of potentially toxic elements (PTEs) through their fixation. In this regard, soil contamination with PTEs such as cadmium (Cd) affects the glomalin production of mycorrhiza fungi. In order to investigate the effect of different levels of Cd on glomalin production of three species of arbuscular mycorrhiza fungi in the presence of sorghum, a greenhouse experiment was conducted in a completely randomized design with factorial arrangement and three repetitions. Factors include four levels of Cd (0, 5, 10, 20 milligrams per kilogram of soil) and second factor included these three types of mycorrhiza: Funneliformis mosseae (FM), Rhizophagus intraradices (RI), and Claroideoglomus etunicatum (CE). The results of this study showed that when increasing soil Cd concentration, shoot dry weight, root colonization percentage, total and easily extractable glomalin decreased while leaf proline concentration, shoot, and root Cd concentration increased. The presence of mycorrhiza in comparison with the control increased the dry weight of shoots and plant height. The results showed that mycorrhizal treatments increased total and easily extractable glomalin compared to the absence of mycorrhiza. Also, the highest amount of glomalin production was observed in two species of FM and CE. Complexation of Cd by total glomalin and easily extractable glomalin was higher in two species of FM and CE rather than RI. The results showed that the use of three species of mycorrhizae reduced the adverse effects of high levels of Cd. Also, the concentration of leaf proline, soluble sugars, shoot, and root Cd concentration was higher in presence of mycorrhizal fungal species than in plant not inoculated with mycorrhizal fungal species. This increase was significant in both FM and CE species. Finally, a notable positive correlation was also observed between glomalin measured by Bradford method and percentage of root colonization., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH, DE part of Springer Nature.)

Arbuscular mycorrhizal fungus (AMF) is generally colonized in plant roots and influences the migration of mineral elements such as nitrogen (N) in soils. However, its effect on N leaching loss in red soils is limited. In the present study, red soils were collected from wasteland, farmland, and slopeland in the Yunnan Plateau. Maize, as a host plant, was cultured in a dual-compartment cultivation system. There were mycorrhizal and hyphal compartments for the AMF inoculation treatment and root and soil compartments for the non-inoculation treatment. The N concentration and uptake in maize, N concentration in pore water within two depth (0-20 and 20-40 cm), and N leaching losses from soil under simulated heavy rainfall (40 and 80 mm/h) were analyzed. Results showed that AMF inoculation significantly enhanced the biomass and N uptake in maize. Compared with the root and soil compartments, the N concentrations in pore water and their leaching losses from the mycorrhizal and hyphal compartments were decreased by 48-77% and 51-74%, respectively. Moreover, significant or extremely significantly positive correlations were observed between the N concentrations in pore water with the N leaching losses from soil. The three-way ANOVA showed that AMF highly significantly decreased N concentrations in pore water and their leaching losses from wasteland, farmland, and slopeland; rainfall intensity had strong influences on the N concentration in pore water from farmland and N leaching losses from wasteland and farmland, whereas the maize root's effect was insignificant. The study indicated that the AMF-induced decreases in the N leaching loss from red soils were caused by increased N uptake by maize and decreased N concentrations in pore water. These results have implications for reducing nutrient leaching loss through the management of beneficial microorganisms in soils.

Little attention has been paid to the combined effects of arbuscular mycorrhizae (AM) fungus and composted manure on heavy metal bioavailability and its uptake by plants grown in heavy metal-contaminated soils from electronic-waste (e-waste) recycling sites. A greenhouse pot experiment was conducted to investigate the effects of AM fungus, composted pig manure (CM) and AM fungus + CM (ACM) on the growth of ryegrass and uptake of Cd and Zn in the soil collected from an e-waste recycling site. The calcium chloride (CaCl 2 ) and Tessier sequential extraction procedure were adopted to evaluate the bioavailability and chemical speciation of Cd and Zn in the soil. Results showed that the application of CM and ACM significantly increased the pH but decreased the CaCl 2 -extractable Cd and Zn concentrations in the rhizosphere and bulk soils. ACM treatment significantly shifted Cd from exchangeable fraction to other more stable fractions, and transformed the exchangeable Zn fraction to the carbonate-bound and reducible iron and manganese-bound fractions. Furthermore, the application of ACM can enhance the growth of plant shoots, and decrease the uptake of Cd and Zn in the ryegrass plants. This work suggests that AM fungus in combination with CM amendment may be a potential method for not only remediation of soil Cd and Zn pollution, but also reduction of Cd and Zn uptake by ryegrass grown in the soil from e-waste recycling sites.

The current study was conducted to determine the combined performance of soil micro- and macro-organisms to stimulate the growth and lead (Pb) uptake of Bermuda grass (Cynodon dactylon (L.) Persi.) in a soil polluted with Pb-mining activities. Plants were inoculated with a mixture of arbuscular mycorrhizal (AM) fungal species, plant growth-promoting rhizobacteria (PGPR) species, and epigeic earthworms (Eisenia fetida) either alone or in combination. Results demonstrated antagonistic interactions between AM fungi and PGPR or between AM fungi and earthworms on the growth of mycorrhizal plants by increasing the availability of both phosphorus (P) and Pb in the soil solution and the subsequent reduction of mycorrhizal root colonization following inoculation of PGPR or earthworms. Plant biomass was negatively correlated with soil-available Pb, but positively with the percentage of root colonization by AM fungi. Additionally, mycorrhizal root colonization was negatively correlated with soil-available P and Pb concentrations. The triple inoculation of AM fungi with PGPR and epigeic earthworms as a bioaugmentation tool could result in a synergistic interaction effect on plant Pb bioaccumulation and uptake, enhancing the efficiency of phytoremediation and eco-restoration of Pb-polluted sites. In conclusion, the use of Bermuda grass in association with functionally dissimilar soil organisms demonstrated a high effectiveness for Pb in situ phytoremediation, specifically Pb phytostabilization, to reduce Pb mobilization in the environment.

Due to the increase of cadmium (Cd)-contaminated land area worldwide, effective measures should be taken to minimize the Cd bioavailability in crops. A study was performed to explore the effectiveness of biochar pyrolyzed from rice straw at 400 °C alone or combined with AM fungi (Funneliformis mosseae) on the corn growth and Cd uptake in corn in Cd-contaminated soil with different levels of phosphorus supplies. The results showed that biochar significantly reduced 66% and 38% of Cd uptake in shoot and root respectively (P < 0.001) attributed to the increase of soil pH and dissolved organic matter. In contrast, AM fungi inoculation of corn plants had little effect on Cd bioavailability due to the AM was suppressed by the highly contaminated acid soil (31.76 mg/kg), and had neither synergistic effect with biochar on decreasing the Cd bioavailability with high or low phosphorus supplies. This study demonstrated that biochar application could be a promising method to immobilize Cd in the contaminated soil to ensure the safety of agro-product while high Cd-contaminated soil would suppress the growth of mycorrhizae, so this remains an open question to be further studied.

Due to the vegetation destruction and soil desertification caused by excessive exploitation at Ganzhou ion-type rare earth mine in the mid-1980s, it is essential to carry out ecological remediation. The symbiotic mycorrhiza formed by the developed perennial ryegrass (Lolium perenne L.) roots infected with arbuscular mycorrhizal fungi (AMF) can significantly improve the growth and resistance of plants. In this study, the combination of symbiotic mycorrhiza and soil modifier was used to construct the ryegrass-AMF-soil modifier combined remediation technology, which achieved effective ecological remediation of soil tailings. The orthogonal experiment of soil modifier showed that the most efficient formula for ryegrass biomass, soil organic matter, soil alkaline hydrolysis, soil available phosphorus, and soil pH was 5 g/kg sepiolite, 3 g/kg chicken manure, 2 g/kg humic acid, and 2 g/kg biochar (A 4 B 3 C 3 D 3 ), and chicken manure (B), humic acid (C), and biochar (D) had significant effects on the improvement of ryegrass biomass, soil organic matter, soil alkaline nitrogen, and soil available phosphorus. Sepiolite (A) had a significant improvement in soil pH. Furthermore, the AMF infection results indicated that Glomus moss (G.m.) had higher affinity with ryegrass. The T4 treatment-combined remediation using G.m. inoculation had the most significant effect on ryegrass growth; plant height increased by 39.19% compared with T1 treatment-inoculation using G.m. Under combined remediation, soil pH, organic matter, alkali nitrogen, and effective phosphorus content also significantly improved after combined treatment. Under G.m. inoculation treatment (T4 treatment), the soil nutrient content reached the three criteria of the soil nutrient grading standard.

Heavy metals cause serious problems in the environment, and they can be accumulated in organisms, especially in the higher fungi. The concentration of Ni, Cr, Pb, Cd, and Hg in 10 species of edible mushrooms in Medvednica Nature Park, Croatia was therefore determined. In addition, the similarity between the studied species was determined by cluster analysis based on concentrations of the aforementioned metals in the fruiting bodies. The contents of nickel, chromium, lead, cadmium, and mercury in the fruiting bodies of mushrooms were obtained by X-ray fluorescence spectrometry. The highest concentrations of Ni (3.62 mg kg(-1)), Cr (3.01 mg kg(-1)), and Cd (2.67 mg kg(-1)) were determined in Agaricus campestris. The highest concentration of Pb (1.67 mg kg(-1)) was determined in Macrolepiota procera, and the highest concentration of Hg (2.39 mg kg(-1)) was determined in Boletus edulis. The concentration of all heavy metals significantly differed (p < 0.001) between examined saprophytic and ectomycorrhizal mushrooms. Considering anatomical part of the fruiting body (cap-stipe), a considerably higher concentration of the analyzed elements was found in the cap for all mushroom species. According to calculated bioconcentration factors, all the examined species were found to be bioexclusors of Ni, Cr, and Pb and bioaccumulators of Cd and Hg. Cluster analysis performed on the basis of the accumulation of the studied metals revealed great phenotypic similarity of mushroom species belonging to the same genus and partial similarity of species of the same ecological affiliation.