The coexistence of arbuscular mycorrhizal fungi and dark septate endophytes synergistically enhanced the cadmium tolerance of maize.

Introduction: Arbuscular mycorrhizal fungi (AMF) and dark septate endophytic fungi (DSEs) generally coexist in the roots of plants. However, our understanding of the effects of their coexistence on plant growth and stress resistance is limited. Methods: In the present study, the effects of single and dual inoculation of AMF and DSE on the growth, photosynthetic physiology, glutathione (GSH) metabolism, endogenous hormones, and cadmium (Cd) content of maize under 25 mg•kg-1 Cd stress were investigated. Results: Compared with that after the non-inoculation treatment, AMF+DSE co-inoculation significantly increased the photosynthetic rate (Pn) of maize leaves; promoted root GSH metabolism; increased the root GSH concentration and activity of γ-glutamyl cysteine synthase (γ-GCS), ATP sulfatase (ATPS) and sulfite reductase (SIR) by 215%, 117%, 50%, and 36%, respectively; and increased the concentration of endogenous hormones in roots, with increases in zeatin (ZR), indole-3 acetic acid (IAA), and abscisic acid (ABA) by 81%, 209%, and 72%, respectively. AMF inoculation, DSE inoculation and AMF+DSE co-inoculation significantly increased maize biomass, and single inoculation with AMF or DSE increased the Cd concentration in roots by 104% or 120%, respectively. Moreover, significant or highly significant positive correlations were observed between the contents of ZR, IAA, and ABA and the activities of γ-GCS, ATPS, and SIR and the glutathione (GSH) content. There were significant or highly significant positive interactions between AMF and DSE on the Pn of leaves, root GSH metabolism, and endogenous hormone contents according to two-way analysis of variance. Therefore, the coexistence of AMF and DSE synergistically enhanced the Cd tolerance of maize.

Urease-producing bacteria with plant growth-promoting ability that may tolerate and remove cadmium from aqueous solution.

Urease-producing bacteria (UPB) are widely present in soil and play an important role in soil ecosystems. In this study, 65 UPB strains were isolated from cadmium (Cd)-polluted soil around a lead-zinc mine in Yunnan Province, China. The Cd tolerance, removal of Cd from aqueous solution, production of indoleacetic acid (IAA) and plant growth-promoting effects of these materials were investigated. The results indicate that among the 65 UPB strains, four strains with IAA-producing ability were screened and identified as Bacillus thuringiensis W6-11, B. cereus C7-4, Serratia marcescens W11-10, and S. marcescens C5-6. Among the four strains, B. cereus C7-4 had the highest Cd tolerance, median effect concentration (EC50) of 59.94 mg/L. Under Cd 5 mg/L, S. marcescens C5-6 had the highest Cd removal from aqueous solution, up to 69.83%. Under Cd 25 mg/kg, inoculation with B. cereus C7-4 significantly promoted maize growth in a sand pot by increasing the root volume, root surface area, and number of root branches by 22%, 29%, and 20%, respectively, and plant height and biomass by 16% and 36%, respectively, and significantly increasing Cd uptake in the maize roots. Therefore, UPB is a potential resource for enhancing plant adaptability to Cd stress in plants with Cd-polluted habitats.

This study utilized urease-producing bacteria screened from the soil of lead zinc mining areas in Yunnan, China as the research object, enriching the microbial resources in Yunnan. In addition, this article verified the IAA production ability and cadmium removal ability of urease-producing bacteria, and screened out bifunctional urease-producing bacteria that have potential in cadmium pollution control and plant growth promotion.

Organic Materials Promote Rhododendron simsii Growth and Rhizosphere Soil Properties in a Lead-Zinc Mining Wasteland.

The mining of metal minerals generates considerable mining wasteland areas, which are characterized by poor soil properties that hinder plant growth. In this study, a field plot experiment was carried out in the mining wasteland of the Lanping lead-zinc mine in Yunnan Province to study the effects of applying three organic materials-biochar (B), organic fertilizer (OF), and sludge (S)-at concentrations of 1% (mass fraction), on promoting the soil of mining wasteland and the growth of two plant varieties (Huolieniao and Yingshanhong). The results showed that the amount of available nutrients in the surface soil of a mining wasteland could be considerably increased by S and OF compared to the control check (CK). In the rhizosphere soils of two Rhododendron simsii varieties, the application of S increased the available phosphorus (P) content by 66.4% to 108.8% and the alkali-hydrolyzed nitrogen (N) content by 61.7% to 295.5%. However, the contents of available cadmium (Cd) and available lead (Pb) were reduced by 17.1% to 32.0% and 14.8% to 19.0%, respectively. Moreover, three organic materials increased the photosynthetic rate and biomass of two R. simsii varieties. Specifically, OF and S were found to significantly increase the biomass of R. simsii. Organic materials have direct impacts on the increased plant height and biomass of R. simsii. Additionally, organic materials indirectly contribute to the growth of R. simsii by reducing the content of available Cd and available Pb in rhizosphere soil while increasing the content of available nutrients according to the structural equation model (SEM). Overall, S can stabilize Cd and Pb, increase soil nutrient contents, and promote the growth of R. simsii effectively, and has great potential in the vegetation reconstruction of mining wasteland.

Enhanced ultraviolet-B radiation alleviates structural damages on rice leaf caused by Magnaporthe oryzae infection.

Enhanced ultraviolet-B (UV-B) radiation can change the interaction between crops and pathogens. The effects of single and compound stresses of enhanced UV-B radiation (5.0 kJ·m-2) and Magnaporthe oryzae on the morphology, anatomy, and ultrastructure of rice leaves were investigated. M. oryzae infection decreased the leaf area and thickness, reduced the stomatal area and density, and caused damages to the leaf ultrastructure, such as cytoplasm-cell wall separation, atrophy and sinking of fan-shaped bulliform cells, and chloroplast deformation. The enhanced UV-B radiation supplied before or during M. oryzae infection remarkably decreased the mycelia number of M. oryzae in leaf epidermis, increased the leaf area, leaf thickness, stomatal density, and mastoid number; and alleviated the ultrastructural damages induced by M. oryzae to keep an integral chloroplast. While the UV-B radiation was supplied after M. oryzae infection, its alleviation effects on the damages induced by M. oryzae infection on the morphology and structure of rice leaf were attenuated. Thus, the alleviation of enhanced UV-B radiation on damages induced by M. oryzae infection on rice leaves was related to its application period. The enhanced UV-B radiation supplied before or during M. oryzae infection allowed the rice leaf to resist M. oryzae infection.

An arbuscular mycorrhizal fungus differentially regulates root traits and cadmium uptake in two maize varieties.

Arbuscular mycorrhizal fungi (AMF) are symbiotic fungi that colonize plant roots, and they are more common in Cd-polluted habitats. However, there is limited understanding of the response of root traits and cadmium (Cd) uptake to AMF in different crop varieties. Two maize varieties, Panyu 3 and Ludan 8, with high and low Cd uptake capacities, respectively, were cultivated as host plants in a pot experiment with Cd-polluted soil (17.1 mg/kg Cd). The effects of AMF on the growth, mineral nutrient concentration, root traits, phytohormone concentrations and Cd uptake of the two maize varieties and their comprehensive response to AMF fungal inoculation were investigated. AMF improved growth, mineral nutrient levels and root morphology and increased lignin and phytohormone concentrations in roots and Cd uptake in the two maize varieties. However, the two maize varieties, Panyu 3 and Ludan 8, had different responses to AMF, and their comprehensive response indices were 753.6% and 389.4%, respectively. The root biomass, branch number, abscisic acid concentrations, lignin concentrations and Cd uptake of maize Panyu 3 increased by 151.1%, 28.6%, 139.7%, 99.5% and 84.7%, respectively. The root biomass, average diameter, auxin concentration, lignin concentration and Cd uptake of maize Ludan 8 increased by 168.7%, 31.8%, 31.4%, 41.7% and 136.7%, respectively. Moreover, Cd uptake in roots presented very significant positive correlations with the average root diameter and abscisic acid concentration. A structural equation model indicated that the root abscisic acid concentration and root surface area had positive effects on Cd uptake by the Panyu 3 maize roots; the root abscisic acid concentration and root tip number had positive effects on Cd uptake by the Ludan 8 maize roots. Thus, AMF differentially regulated Cd uptake in the two maize varieties, and the regulatory effect was closely related to root traits and phytohormone concentrations.

A Dark Septate Endophyte Improves Cadmium Tolerance of Maize by Modifying Root Morphology and Promoting Cadmium Binding to the Cell Wall and Phosphate.

Dark septate endophytes (DSEs) can improve the performance of host plants grown in heavy metal-polluted soils, but the mechanism is still unclear. A sand culture experiment was performed to investigate the effects of a DSE strain (Exophiala pisciphila) on maize growth, root morphology, and cadmium (Cd) uptake under Cd stress at different concentrations (0, 5, 10, and 20 mg·kg-1). The results indicated that the DSE significantly improved the Cd tolerance of maize, causing increases in biomass, plant height, and root morphology (length, tips, branch, and crossing number); enhancing the Cd retention in roots with a decrease in the transfer coefficient of Cd in maize plants; and increasing the Cd proportion in the cell wall by 16.0-25.6%. In addition, DSE significantly changed the chemical forms of Cd in maize roots, resulting in decreases in the proportions of pectates and protein-integrated Cd by 15.6-32.4%, but an increase in the proportion of insoluble phosphate Cd by 33.3-83.3%. The correlation analysis revealed a significantly positive relationship between the root morphology and the proportions of insoluble phosphate Cd and Cd in the cell wall. Therefore, the DSE improved the Cd tolerance of plants both by modifying root morphology, and by promoting Cd binding to the cell walls and forming an insoluble phosphate Cd of lower activity. These results of this study provide comprehensive evidence for the mechanisms by which DSE colonization enhances Cd tolerance in maize in root morphology with Cd subcellular distribution and chemical forms.

Dark septate endophyte Exophiala pisciphila promotes maize growth and alleviates cadmium toxicity.

Dark septate endophytes (DSE) are typical root endophytes with the ability to enhance plant growth and tolerance to heavy metals, but the underlying mechanisms are unclear. Here, the physiological and molecular mechanisms of a DSE strain, Exophiala pisciphila, in mitigating cadmium (Cd, 20 mg/kg) toxicity in maize were investigated. Our results showed, under Cd stress, E. pisciphila inoculation enhanced the biomass of maize and reduced both inorganic and soluble forms of Cd (high toxicity) by 52.6% in maize leaves, which may be potentially contributing to Cd toxicity mitigation. Besides, E. pisciphila inoculation significantly affected the expression of genes involved in the signal transduction and polar transport of phytohormone, and then affected abscisic acid (ABA) and indole-3-acetic acid (IAA) contents in maize roots, which was the main reason for promoting maize growth. In addition, E. pisciphila also made a 27% increase in lignin content by regulating the expression of genes involved in the synthesis of it, which was beneficial to hinder the transport of Cd. In addition, E. pisciphila inoculation also activated glutathione metabolism by the up-regulation of genes related to glutathione S-transferase. This study helps to elucidate the functions of E. pisciphila under Cd stress, sheds light on the mechanism of detoxifying Cd and provides new insights into the protection of crops from heavy metals.

The effects of different iron and phosphorus treatments on the formation and morphology of iron plaque in rice roots (Oryza sativa L).

Introduction: Rice (Oryza sativa L.) is a pivotal cereal crop worldwide. It relies heavily on the presence of iron plaque on its root surfaces for optimal growth and enhanced stress resistance across diverse environmental conditions. Method: To study the crystallographic aspects of iron plaque formation on rice roots, the concentrations of Fe2+ and PO4 3- were controlled in this study. The effects of these treatments were assessed through comprehensive analyzes encompassing root growth status, root surface iron concentration, root vitality, enzyme activities, and microstructural characteristics using advanced techniques such as root analysis, scanning electron microscopy (SEM), and ultrathin section transmission electron microscopy (TEM). Results: The results demonstrated that an increase in the Fe2+ concentration or a decrease in the PO4 3- concentration in the nutrient solution led to improvements in various root growth indicators. There was an elevation in the DCB (dithionite-citrate-bicarbonate) iron content within the roots, enhanced root vitality, and a significant increase in the activities of the superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) enzymes. Moreover, as the Fe2+ concentration increased, amorphous iron oxide minerals on the root surface were gradually transformed into ferrihydrite particles with sizes of approximately 200 nm and goethite particles with sizes of approximately 5 µm. This study showed that an increase in the Fe2+ concentration and a decrease in the PO4 3- concentration led to the formation of substantial iron plaque on the root surfaces. It is noteworthy that there was a distinct gap ranging from 0.5 to 3 µm between the iron plaque formed through PO4 3- treatment and the cellular layer of the root surface. Discussion: This study elucidated the impacts of Fe2+ and PO4 3- treatments on the formation, structure, and morphology of the iron plaque while discerning variations in the spatial proximity between the iron plaque and root surface under different treatment conditions.

Contamination and Health Risk Assessment of Heavy Metals in Soil and Ditch Sediments in Long-Term Mine Wastes Area.

The ecological and health risks posed by wastes discharged from mining areas to the environment and human health has aroused concern. 114 soil samples were collected from nine areas of long-term mine waste land in northwestern Yunnan to assess the pollution characteristics, ecological and health risks of heavy metals. The result revealed that the geo-accumulation indexes were Cd (4.00) > Pb (3.18) > Zn (1.87) > Cu (0.25). Semi-variance analysis revealed that Cd and Cu showed moderate spatial dependency, whereas Pb and Zn showed strong spatial dependency. Cd posed an extreme potential ecological risk. Slopes and ditches were extreme potential ecological risk areas. Non-carcinogenic risk to children from Pb and Carcinogenic risk to adult and children from Cd was non-negligible and direct ingestion was the major source. This study provided a scientific basis for policymakers in management and exposure reduction.

Arbuscular Mycorrhizal Fungi Reduce Cadmium Leaching from Sand Columns by Reducing Availability and Enhancing Uptake by Maize Roots.

To explore the effect of arbuscular mycorrhizal fungi (AMF) on the environmental migration of cadmium (Cd), a sand column-maize system containing 20 mg·L-1 Cd solution was used to investigate the AMF effect on maize growth, Cd uptake by maize, Cd adsorption by sand and Cd leaching loss. The results showed that AMF significantly increased the content of EE-GRSP and T-GRSP by 34.9% and 37.2%, respectively; the secretion of malonic acid, oxalic acid and succinic acid increased by 154.2%, 54.0% and 11.0%, respectively; the secretion of acetic acid and citric acid increased by 95.5% and 59.9%, respectively; and the length, surface area, volume, tip number and cross number of maize roots decreased by 10%, 15%, 17%, 20% and 36.4%, respectively. AMF significantly increased Cd adsorption by sand by 6.2%, Cd uptake by maize by 68.1%, and Cd leaching loss by 84.6%. In the sand column-maize system, 92.3% of the total Cd was adsorbed by sand, 5.9% was taken up by maize and 1.8% was lost due to leaching. Moreover, Cd adsorption by sand was significantly positively correlated with the GRSP content and oxalic acid secretion, and Cd uptake by roots was significantly negatively correlated with Cd leaching loss. Overall, AMF reduced the loss of Cd in the leaching solution by promoting the release of oxalic acid and GRSP, increasing the adsorption of Cd in the sand and fixing the Cd in the plant to the roots.

Effects of an Arbuscular Mycorrhizal Fungus on the Growth of and Cadmium Uptake in Maize Grown on Polluted Wasteland, Farmland and Slopeland Soils in a Lead-Zinc Mining Area.

Arbuscular mycorrhizal fungi (AMF) exist widely in soil polluted by heavy metals and have significant effects on plant growth and cadmium (Cd) uptake. Cd contents differ among wasteland, farmland and slopeland soils in a lead-zinc mining area in Yunnan Province, Southwest China. The effects of AMF on maize growth, root morphology, low-molecular-weight organic acid (LMWOA) concentrations and Cd uptake were investigated via a root-bag experiment. The results show that AMF increased maize growth on Cd-polluted soils, resulting in increases in root length, surface area, volume and branch number, with the effects being stronger in farmland than in wasteland and slopeland soils; increased malic acid and succinic acid secretion 1.3-fold and 1.1-fold, respectively, in roots on farmland soil; enhanced the iron- and manganese-oxidized Cd concentration by 22.6%, and decreased the organic-bound Cd concentration by 12.9% in the maize rhizosphere on farmland soil; and increased Cd uptake 12.5-fold and 1.7-fold in shoots and by 25.7% and 86.6% in roots grown on farmland and slopeland soils, respectively. Moreover, shoot Cd uptake presented significant positive correlations with root surface area and volume and LMWOA concentrations. Thus, these results indicated the possible mechanism that the increased maize Cd uptake induced by AMF was closely related to their effect on root morphology and LMWOA secretion, with the effects varying under different Cd pollution levels.

Suppression of arbuscular mycorrhizal fungi increased lead uptake in maize leaves and loss via surface runoff and interflow from polluted farmland.

Arbuscular mycorrhizal fungi (AMF) are ubiquitous in farmland. But the knowledge on AMF impact on lead (Pb) migration in farmland is limited. A field experiment was conducted in the rainy season (May-October) for two years in a Pb-polluted farmland. Benomyl was used to specifically suppress the native AMF growth in the farmland. The effect of benomyl-induced AMF suppression on the Pb uptake in maize, and Pb loss via surface runoff and interflows (20 cm and 40 cm depth) from the farmland was investigated. The benomyl significantly inhibited the AMF growth, resulting in decreases in the colonization rate, spore number, and contents of total and easily extractable glomalin-related soil protein (GRSP); and promoted the Pb migration into maize shoots and mainly enriched in leaves. The particulate Pb accounted for 83.2%-90.6% of Pb loss via surface runoff, while the proportion of particulate Pb loss via interflow was decreased and the proportion of dissolved Pb loss increased with the increase of soil depth. The AMF suppression led to a decrease in dissolved Pb concentration and loss, but an increase in particulate Pb concentration and loss, and enhanced the total Pb loss via surface runoff and interflows. Moreover, significant or very significant negative correlations were observed between the AMF colonization rate in roots with the Pb uptake in leaves, and the content of easily extractable GRSP with the particulate Pb loss. These results indicated the native AMF contributed to immobilizing Pb in soil and inhibited its migration to crops and the surrounding environment.

Root-associated microbiota drive phytoremediation strategies to lead of Sonchus Asper (L.) Hill as revealed by intercropping-induced modifications of the rhizosphere microbiome.

Intercropping or assistant endophytes promote phytoremediation capacities of hyperaccumulators and enhance their tolerance to heavy metal (HM) stress. Findings from a previous study showed that intercropping the hyperaccumulator Sonchus asper (L.) Hill grown in HM-contaminated soils with maize improved the remediating properties and indicated an excluder-to-hyperaccumulator switched mode of action towards lead. In the current study, RNA-Seq analysis was conducted on Sonchus roots grown under intercropping or monoculture systems to explore the molecular events underlying this shift in lead sequestering strategy. The findings showed that intercropping only slightly affects S. asper transcriptome but significantly affects expression of root-associated microbial genomes. Further, intercropping triggers significant reshaping of endophytic communities associated with a 'root-to-shoot' transition of lead sequestration and improved phytoremediation capacities of S. asper. These findings indicate that accumulator activities of a weed are partially attributed to the root-associated microbiota, and a complex network of plant-microbe-plant interactions shapes the phytoremediation potential of S. asper. Analysis showed that intercropping may significantly change the structure of root-associated communities resulting in novel remediation properties, thus providing a basis for improving phytoremediation practices to restore contaminated soils.

Root Metabolite Differences in Two Maize Varieties Under Lead (Pb) Stress.

To assess root metabolic differences of maize varieties in their response to lead (Pb) stress, the lead-tolerant variety Huidan No. 4 and the lead-sensitive variety Ludan No. 8 were tested under Pb-free and Pb-stressed conditions. Changes in metabolites were measured using ultra-performance liquid chromatography-mass spectrometry. Pb stress changed the levels of the amino acids proline, glutamine, lysine, and arginine in both varieties, whereas glutamate and phenylalanine levels changed only in Huidan No. 4. Pb stress altered cystine, valine, methionine, and tryptophan levels only in Ludan No. 8. Therefore, the synthesis and decomposition of amino acids may affect the response of maize to Pb stress. The degree of change in differential metabolites for Huidan No. 4 was greater than that for Ludan No. 8. In cell wall subcellular components, increases in superoxide dismutase (SOD), peroxidases (PODs), and Pb concentrations were greater in Huidan No. 4 than in Ludan No. 8. Therefore, the greater Pb tolerance of Huidan No. 4 could be due to better sequestration of Pb in cell walls and more effective removal of reactive oxygen species (ROS) from the plant. The levels of certain metabolites only increased in Ludan No. 8, indicating that Pb-sensitive varieties may use different metabolic pathways to cope with Pb stress. Both varieties showed increased levels of some metabolites related to antioxidant protection and osmotic regulation. This study provides an understanding of maize Pb tolerance mechanisms and a basis for further development of tools for use in maize breeding.

Effects of the Dark Septate Endophyte (DSE) Exophiala pisciphila on the Growth of Root Cell Wall Polysaccharides and the Cadmium Content of Zea mays L. under Cadmium Stress.

This paper aims to investigate the mechanism by which dark septate endophytes (DSEs) enhance cadmium (Cd) tolerance in there host plants. Maize (Zea mays L.) was inoculated with a DSE, Exophiala pisciphila, under Cd stress at different concentrations (0, 5, 10, and 20 mg·kg-1). The results show that, under 20 mg/kg Cd stress, DSE significantly increased maize biomass and plant height, indicating that DSE colonization can be utilized to increase the Cd tolerance of host plants. More Cd was retained in DSE-inoculated roots, especially that fixed in the root cell wall (RCW). The capability of DSE to induce a higher Cd holding capacity in the RCW is caused by modulation of the total sugar and uronic acid of DSE-colonized RCW, mainly the pectin and hemicellulose fractions. The fourier-transform spectroscopy analysis results show that carboxyl, hydroxyl, and acidic groups are involved in Cd retention in the DSE-inoculated RCW. The promotion of the growth of maize and improvement in its tolerance to Cd due to DSEs are related to restriction of the translocation of Cd from roots to shoots; resistance of Cd uptake Cd inside cells; and the increase in RCW-integrated Cd through modulating RCW polysaccharide components.

Effect of an arbuscular mycorrhizal fungus on maize growth and cadmium migration in a sand column.

The ecological role of arbuscular mycorrhizal fungi (AMF) on altering cadmium (Cd) migration in polluted soil is still unresolved. The present experiment aimed to clarify whether AMF can reduce Cd loss due to leaching at different Cd concentrations (0, 5, 10, and 15 mg L-1) with maize as a host plant cultured in a sand column. The effects of the arbuscular mycorrhizal fungus Funneliformis mosseae on the root morphology, exudate content, and Cd uptake by maize and Cd loss due to leaching were investigated. The AMF altered the root morphology and exudate content of the maize, resulting in increases in the root length, volume, surface area, tips and branch number and in the contents of soluble sugars, proteins, and amino acids in the root exudates, and the AMF increased maize biomass and Cd uptake by 22.0-31.0%. Moreover, the AMF significantly increased the contents of total and easily extractable glomalin-related soil protein (GRSP), increased Cd adsorption by sand particles and decreased the Cd concentration in the solution at a depth of 20 cm, resulting in a 67.5-97.2% decrease in the Cd loss due to leaching from the sand column. Furthermore, the root exudate content was very significantly positively correlated with Cd adsorption by the sand particles. Root length was significantly positively correlated with Cd uptake by the maize roots, but the average root diameter was very significantly negatively correlated with Cd uptake by maize. Thus, the AMF altered Cd migration by increasing the contents of GRSP and exudates and root morphology, which contributed to reducing the Cd concentration in the solution and Cd loss due to leaching from the sand column. Taken together, these results indicated that AMF serve an ecological function in reducing Cd loss due to leaching from polluted soil.

Accumulation and Transfer of Cadmium Isotope (112Cd) by Sonchus asper Intercropped with Vicia faba and Implications for Phytoremediation.

Accumulation and transfer of Cd by Sonchus asper intercropped with a legume crop, Vicia faba were determined via 112Cd as a tracer to assess the potential of Sonchus asper as a hyperaccumulator. In this study, Sonchus asper and Vicia faba were planted side by side in soils amended with arbuscular mycorrhizae, and 112Cd was applied to either Sonchus asper or Vicia faba planted soils while the neighboring plant received 112Cd across a nylon net impermeable to the roots. Mean concentration of 112Cd in the shoot of Sonchus asper was 7.0 times higher than Vicia faba. The translocation factor of 112Cd in Sonchus asper were 39 and 400 times higher than in Vicia faba under the 112Cd direct and indirect treatments, respectively. The results suggested that the intercropping of Sonchus asper as a hyperaccumulator with Vicia faba, might be a feasible approach for phytoremediation of Cd contaminated soil.

Arbuscular mycorrhizal fungus-induced decrease in nitrogen concentration in pore water and nitrogen leaching loss from red soil under simulated heavy rainfall.

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.

An arbuscular mycorrhizal fungus increased the macroaggregate proportion and reduced cadmium leaching from polluted soil.

NOVELTY STATEMENT: AMF significantly increased the GRSP content and the macroaggregate proportion in soil, which contributed to reducing the Cd concentration in pore water and its leaching loss from soil.