Antimony uptake, efflux and speciation in arsenic hyperaccumulator Pteris vittata

Managing antimony pollution: Insights into Soil-Plant system dynamics and remediation Strategies

Researchers are increasingly concerned about antimony (Sb) in ecosystems and the environment. Sb primarily enters the environment through anthropogenic (urbanization, industries, coal mining, cars, and biosolid wastes) and geological (natural and chemical weathering of parent material, leaching, and wet deposition) processes. Sb is a hazardous metal that can potentially harm human health. However, no comprehensive information is available on its sources, how it behaves in soil, and its bioaccumulation. Thus, this study reviews more than 160 peer-reviewed studies examining Sb's origins, geochemical distribution and speciation in soil, biogeochemical mechanisms regulating Sb mobilization, bioavailability, and plant phytotoxicity. In addition, Sb exposure effects plant physio-morphological and biochemical attributes were investigated. The toxicity of Sb has a pronounced impact on various aspects of plant life, including a reduction in seed germination and impeding plant growth and development, resulting from restricted essential nutrient uptake, oxidative damages, disruption of photosynthetic system, and amino acid and protein synthesis. Various widely employed methods for Sb remediation, such as organic manure and compost, coal fly ash, biochar, phytoremediation, microbial-based bioremediation, micronutrients, clay minerals, and nanoremediation, are reviewed with a critical assessment of their effectiveness, cost-efficiency, and suitability for use in agricultural soils. This review shows how plants deal with Sb stress, providing insights into lowering Sb levels in the environment and lessening risks to ecosystems and human health along the food chain. Examining different methods like bioaccumulation, bio-sorption, electrostatic attraction, and complexation actively works to reduce toxicity in contaminated agricultural soil caused by Sb. In the end, the exploration of recent advancements in genetics and molecular biology techniques are highlighted, which offers valuable insights into combating Sb toxicity. In conclusion, the findings of this comprehensive review should help develop innovative and useful strategies for minimizing Sb absorption and contamination and thus successfully managing Sb-polluted soil and plants to reduce environmental and public health risks.

Rare earth elements applied to phytoremediation: Enhanced endocytosis promotes remediation of antimony contamination with different valence levels in Solanum nigrum L

Antimony (Sb) pollution poses a noteworthy risk to human health and ecosystem sustainability, therefore effective, eco-friendly, and widely accepted restoration methods are urgently needed. This study introduces a new approach of using La(III) foliar application on Solanum nigrum L. (S. nigrum), a cadmium hyperaccumulator, to improve its photosynthetic and root systems under Sb stress, resulting in a higher biomass. Notably, La(III) also enhances endocytosis in root cells, facilitating efficient and non-selective remediation of both Sb(III) and Sb(V) forms. The absorption of Sb by root cell endocytosis was observed visually with a confocal laser scanning microscope. The subcellular distribution of Sb in the cell wall of S. nigrum is reduced. And the antioxidant enzyme activity system is improved, resulting in an enhanced Sb tolerance in S. nigrum. Based on the existing bibliometric analysis, this paper identified optimal conditions for S. nigrum to achieve maximum translocation and bioconcentration factor values for Sb. The foliar application of La(III) on plants treated with Sb(III), Sb(V), and a combination of both resulted in translocation factor values of 0.89, 1.2, 1.13 and bioconcentration factor values of 11.3, 12.81, 14.54, respectively. Our work suggests that La(III)-enhanced endocytosis of S. nigrum root cells is a promising remediation strategy for Sb-contaminated environments.

Enzymes Involved in Antioxidant and Detoxification Processes Present Changes in the Expression Levels of Their Coding Genes under the Stress Caused by the Presence of Antimony in Tomato

Currently, there is an increasing presence of heavy metals and metalloids in soils and water due to anthropogenic activities. However, the biggest problem caused by this increase is the difficulty in recycling these elements and their high permanence in soils. There are plants with great capacity to assimilate these elements or make them less accessible to other organisms. We analyzed the behavior of Solanum lycopersicum L., a crop with great agronomic interest, under the stress caused by antimony (Sb). We evaluated the antioxidant response throughout different exposure times to the metalloid. Our results showed that the enzymes involved in the AsA-GSH cycle show changes in their expression level under the stress caused by Sb but could not find a relationship between the NITROSOGLUTATHIONE REDUCTASE (GSNOR) expression data and nitric oxide (NO) content in tomato roots exposed to Sb. We hypothesize that a better understanding of how these enzymes work could be key to develop more tolerant varieties to this kind of abiotic stress and could explain a greater or lesser phytoremediation capacity. Moreover, we deepened our knowledge about Glutathione S-transferase (GST) and Glutathione Reductase (GR) due to their involvement in the elimination of the xenobiotic component.

Washing antimony and arsenic from agricultural soil with eco-friendly organic acids and the relevant bioavailability assessment

Antimony (Sb) and arsenic (As) contamination in agricultural soil poses human health risks through agricultural products. Soil washing with degradable low molecular weight organic acids (LMWOAs) is an eco-friendly strategy to remediate agricultural soils. In this study, three eco-friendly LMWOAs, oxalic acid (OA), tartaric acid (TA), and citric acid (CA), were used to treat Sb and As co-contaminated agricultural soil from Xikuangshan mine area. The OA, TA, and CA washed out 18.4, 16.8, and 26.6% of Sb and 15.3, 19.9, and 23.8% of As from the agricultural soil, with CA being the most efficient reagent for the soil washing. These organic acids also led to pH decline and macronutrients losses. Fraction analysis using a sequential extraction procedure showed that the three organic acids targeted and decreased the specifically sorbed (F2) (by 19.3-37.6% and 2.41-23.5%), amorphous iron oxide associated (F3) (by 49.1-61.2% and 51.2-70.2%), and crystallized iron oxide associated (F4) (by 12.3-26.0% and 26.1-29.1%) Sb and As. The leachability of Sb and As, as well as their concentrations and bioconcentration factor (BCF) in vegetables reduced due to the soil washing. It demonstrated that the bioavailability of both the elements was decreased by the organic acids washing. The concentrations of Sb and As in typical vegetable species cultivated in CA washed soil were less than the threshold value for consumption safety, while those in OA and TA washed soils were still higher than the value, suggesting that only CA is a potential washing reagent in soil washing for Sb- and As-contaminated agricultural soil.

Investigating the use of Aspergillus niger fermentation broth as a washing treatment for arsenic and antimony co-contaminated soil

High concentrations of arsenic and antimony contamination in soil are a potential risk to the ecological environment and human health. Soil washing can effectively and permanently reduce the soil contamination. This study used Aspergillus niger fermentation broth as a washing agent to remove As and Sb from contaminated soil. Characterization of organic acids in the fermentation broth by high-performance liquid chromatographic (HPLC) and chemically simulated leaching experiments revealed that oxalic acid played a significant role in removing As and Sb from the soil. The effect of washing conditions on the metal removal rate of Aspergillus niger fermentation broth was investigated by batch experiments, and the optimal conditions were determined: no dilution, pH 1, L/S ratio 15:1, and leaching at 25 °C for 3 h. The soils were washed three times under optimal conditions, with 73.78%, 80.84%, and 85.83% removal of arsenic and 65.11%, 76.39%, and 82.06% removal of antimony, respectively. The results of metal speciation distribution in the soil showed that the fermentation broth could effectively remove As and Sb on amorphous Fe/Al hydrous oxides in soil. The analysis of X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) of soils before and after washing showed that the washing of Aspergillus niger fermentation broth had a minor effect on the structural changes of soils. After washing, soil organic matter and soil enzyme activity were increased. Thus, Aspergillus niger fermentation broth shows excellent potential as a washing agent for removing As and Sb from soils.

Antimony uptake and speciation, and associated mechanisms in two As-hyperaccumulators Pteris vittata and Pteris cretica

The behaviors of antimony (Sb) and arsenic (As) in plants are different, though they are chemical analogs. Here, we examined the Sb uptake and speciation in two As-hyperaccumulators P. vittata and P. cretica, which were exposed to 0.5 or 5 mg L^-1 antimonate (SbV) or antimonite (SbIII) under hydroponics for 7 d. Both plants grew better under Sb exposure, especially for P. cretica. The biomass of P. cretica roots increased by 29-46% after exposing to SbV, possibly due to increased S. Further, the Sb content in P. vittata was 17-93% greater than P. cretica, with 2-3 times more SbIII than SbV in both plants and > 92% Sb being concentrated in the roots, showing limited translocation. Under SbV exposure, SbV was dominant in P. vittata roots at 86-94%, while SbIII was predominant in P. cretica roots at 36-95%. P. cretica's stronger reducing ability than P. vittata may be due to arsenate reductases HAC1 and ACR2, which were upregulated in both plants. In short, while effective in Sb accumulation, it is mostly concentrated in the roots for both plants. The differences in their accumulation and speciation may help to better understand Sb behaviors in other plants.

Evaluation of Pollution Level, Spatial Distribution, and Ecological Effects of Antimony in Soils of Mining Areas: A Review

The first global-scale assessment of Sb contamination in soil that was related to mining/smelting activities was conducted based on 91 articles that were published between 1989 and 2021. The geographical variation, the pollution level, the speciation, the influencing factors, and the environmental effects of Sb that were associated with mining/smelting-affected soils were analyzed. The high Sb values mainly occurred in developed (Poland, Italy, Spain, Portugal, New Zealand, Australia) and developing (China, Algeria, Slovakia) countries. Sb concentrations of polluted soil from mining areas that were reported in most countries significantly exceeded the maximum permissible limit that is recommended by WHO, except in Turkey and Macedonia. The soil Sb concentrations decreased in the order of Oceania (29,151 mg/kg) > North Africa (13,022 mg/kg) > Asia (1527 mg/kg) > Europe (858 mg/kg) > South America (37.4 mg/kg). The existing extraction methods for Sb speciation have been classified according to the extractant, however, further research is needed in the standardization of these extraction methods. Modern analytical and characterization technologies, e.g., X-ray absorption spectroscopy, are effective at characterizing chemical speciation. Conditional inference tree (CIT) analysis has shown that the clay content was the major factor that influenced the soil Sb concentration. Non-carcinogenic risks to the public from soil Sb pollution were within the acceptable levels in most regions. An Sb smelter site at the Endeavour Inlet in New Zealand, an abandoned open-pit Sb mine in Djebel Hamimat, Algeria, an old Sb-mining area in Tuscany, Italy, and Hillgrove mine in Australia were selected as the priority control areas. Cynodon dactylon, Boehmeria, Pteris vittata, and Amaranthus paniculatus were found to be potential Sb accumulators. All of the values of bioaccumulation factors for the crops were less than one. However, ingestion of Sb through crop consumption posed potential non-carcinogenic health risks, which should not be neglected. The soil variables (pH, Eh, total sulfur, carbon nitrogen ratio, total organic carbon, and sulfate), the total Sb and the bioavailable Sb, and heavy metal(loid)s (As, Pb, and Fe) were the major parameters affecting the microbial community compositions.

Toxicity of different forms of antimony to rice plants: Photosynthetic electron transfer, gas exchange, photosynthetic efficiency, and carbon assimilation combined with metabolome analysis

Antimony (Sb) is a toxic metalloid, and excess Sb causes damage to the plant photosynthetic system. However, the underlying mechanisms of Sb toxicity in the plant photosynthetic system are not clear. Hydroponic culture experiments were conducted to illustrate the toxicity differences of antimonite [Sb(III)] and antimonate [Sb(V)] to the photosynthetic system in a rice plant (Yangdao No. 6). The results showed that Sb(III) showed a higher toxicity than Sb(V), judging from (1) lower shoot and root biomass, leaf water moisture content, water use efficiency, stomatal conductance, net photosynthetic rate, and transpiration rate; (2) higher water vapor deficit, soluble sugar content, starch content, and oligosaccharide content (sucrose, stachyose, and 1-kestose). To further analyze the direction of the photosynthetic products, we conducted a metabonomic analysis. More glycosyls were allocated to the synthesis pathways of oligosaccharides (sucrose, stachyose, and 1-kestose), anthocyanins, salicylic acid, flavones, flavonols, and lignin under Sb stress to quench excess oxygen free radicals (ROS), strengthen the cell wall structure, rebalance the cell membrane, and/or regulate cell permeability. This study provides a complete mechanism to elucidate the toxicity differences of Sb(III) and Sb(V) by exploring their effects on photosynthesis, saccharide synthesis, and the subsequent flow directions of glycosyls.

Uptake, speciation and detoxification of antimonate and antimonite in As-hyperaccumulator Pteris Cretica L

Antimony (Sb) and arsenic (As) are chemical analogs, but their behaviors in plants are different. To investigate the Sb uptake, translocation and speciation in As-hyperaccumulator P. cretica, a hydroponic experiment was conducted. In this study, P. cretica was exposed to 0.2-strength Hoagland nutrient solution, which contained 0.5 or 5 mg/L antimonite (SbIII) or antimonate (SbV). After 14 d exposure, P. cretica took up 1.4-2.8 times more SbIII than SbV. Since P. cretica was unable to translocate Sb, its roots accumulated >97% Sb with the highest at 7965 mg/kg. In both SbIII and SbV treatments, SbIII was the predominant species in P. cretica, with 90-100% and 46-100% SbIII in the roots. As the first barrier against Sb to enter plant cells, more Sb was accumulated in cell wall than cytosol or organelles. The results suggest that P. cretica may detoxify Sb by reducing SbV to SbIII and immobilizing it in root cell walls. Besides, the presence of SbIII significantly reduced the concentrations of dissolved organic C including organic acids in P. cretica root exudates. Further, increasing Sb levels promoted P accumulation in the plant, especially in the fronds, which may help P. cretica growth. The information from this study shed light on metabolic transformation of Sb in As-hyperaccumulators P. cretica, which helps to better understand Sb uptake and detoxification by plants.

Impacts of typical engineering nanomaterials on the response of rhizobacteria communities and rice (Oryza sativa L.) growths in waterlogged antimony-contaminated soils

The combined eco-risks of Sb (widely presented in soils, especially nearing mining areas) and the engineering nanomaterials (ENMs) (applied in agriculture and soil remediation) still remain uncovered. The current study investigated the impacts of single and combined exposure of CuO, CeO₂ nanoparticles (NPs) and multi-walled carbon nanotube (MWCNTs) with Sb on rice growths and rhizosphere bacterial communities. The results showed that co-exposure of CuO NPs (0.075 wt%) with Sb (III) posed the most adverse impacts on root biomass and branches (up to 66.59% and 70.00% compared to other treatments, respectively). Treatments containing MWCNTs showed insignificant dose-dependent effects, while CeO₂ NPs combined with Sb (III) showed significant synergistic stimulating effects on the fresh weights of root and shoot, by 68.30% and 73.48% (p < 0.05) compared to single Sb exposure, respectively. The rice planting increased the percentage of non-specifically sorbed Sb in soils by 1.50-14.49 than the no-planting stage. Analysis on microbial communities revealed that co-exposure of CuO NPs with Sb (III) induced the greatest adverse impacts on rhizobacteria abundances and community structures at both phylum and genus levels. Therein, significant decrease of Bacteroidetes, Acidobacteria and increase of Firmicutes abundance at the phylum level were observed. This study provided information about the risks of different ENMs released to Sb-contaminated soils under flooded condition on both crops and bacterial communities.

Effects of copper and arsenic on their uptake and distribution in As-hyperaccumulator Pteris vittata

Arsenic (As) and copper (Cu) are common co-contaminates in soils. However, their interactive effects on their accumulation and distribution in As-hyperaccumulator Pteris vittata are poorly understood. A hydroponic experiment was conducted with As being 0, 5, or 50 μM and Cu being 0.32, 3.2, or 32 μM to evaluate their phytotoxicity, accumulation, and distribution in P. vittata. In addition, As and Cu uptake kinetics were examined using the Michaelis-Menten kinetics model. Total As and Cu concentrations in P. vittata were up to 487 and 1355 mg kg^-1. About 39-81% of the As was in the fronds compared to 0.6-18% for Cu. At 50 μM As, increasing Cu concentration from 0.32 to 32 μM increased root As while decreasing frond As concentrations, with the translocation factor (ratio of As in fronds to roots) being reduced from 4.0 to 0.31. In contrast, As did not affect Cu accumulation in P. vittata. Michaelis constant K_m value for As was higher than that of Cu (6.49-24.9 vs. 0.43-3.36), consistent with higher Cu uptake than As. Besides, Cu reduced root K but increased P levels in the roots, whereas As increased the K and P concentrations in the fronds. Our results suggest that P. vittata accumulated more Cu than As in the roots, contributing to its low As translocation. As such, high levels of Cu are likely to reduce As uptake by P. vittata during phytoremediation of As-contaminated sites.

Kinetics of antimony biogeochemical processes under pre-definite anaerobic and aerobic conditions in a paddy soil

While the transformation of antimony (Sb) in paddy soil has been previously investigated, the biogeochemical processes of highly chemical active Sb in the soil remain poorly understood. In addition, there is a lack of quantitative understanding of Sb transformation in soil. Therefore, in this study, the kinetics of exogenous Sb in paddy soils were investigated under anaerobic and aerobic incubation conditions. The dissolved Sb(V) and the Sb(V) extracted by diffusive gradient technique decreased under anaerobic conditions and then increased under aerobic conditions. The redox reaction of Sb occurred, and Sb bioavailability significantly decreased after 55 days of incubation. The kinetics of Fe and the scanning transmission electron microscopy analysis revealed that the Fe oxides were reduced and became dispersed under anaerobic conditions, whereas they were oxidized and re-aggregated during the aerobic stage. In addition, the redox processes of sulfur and nitrogen were detected under both anaerobic and aerobic conditions. Based on these observations, a simplified kinetic model was established to distinguish the relative contributions of the transformation processes. The bioavailability of Sb was controlled by immobilization as a result of S reduction and by mobilization as a result of Fe reductive dissolution and S oxidation, rather than the pH. These processes coupled with the redox reaction of Sb jointly resulted in the complex behavior of Sb transformation under anaerobic and aerobic conditions. The model-based method and findings of this study provide a comprehensive understanding of the Sb transformation in a complex soil biogeochemical system under changing redox conditions.

Effects of arbuscular mycorrhizal fungi on frond antimony enrichment, morphology, and proteomics in Pteris cretica var. nervosa during antimony phytoremediation

Pteris cretica var. nervosa is a dominant fern species found in antimony (Sb) mining areas, capable of forming symbiosis with arbuscular mycorrhizal fungi (AMF), especially with those members of the Glomus genus. Despite this fern's relevance and the potential contribution of mycorrhizal symbiosis to phytoremediation, the AMF's impact on P. var. nervosa phytoremediation of Sb remains unknown. Here, we exposed P. var. nervosa to different concentrations of Sb for 6 months. Our results showed that Sb reduced shoot biomass, enlarged the root/shoot ratio, and disrupted the fronds' intracellular structure. AMF inoculation, however, was able to moderate these phenotypic changes and increased the accumulation level of Sb in plants. From a proteomics analysis of this plant's fronds, a total of 283 proteins were identified. Notably, those proteins with catalytic function, carbon fixing and ATP metabolic function were highly enriched. K-means clustering demonstrated protein-changing patterns involved in multiple metabolic pathways during exposure to Sb. Further, these patterns can be moderated by AMF inoculation. Pearson correlations were used to assess the plant biomarkers-soil Sb relationships; This revealed a strong correlation between ribosome alteration and the root/shoot ratio when inoculated with AMF, and a positive correlation between photosynthesis proteins and chlorophyll (SPAD value). Our results indicate AMF could moderate the fronds impairment by maintaining the sufficient protein levels for ribosomal functioning, photosynthesis activity and to counter ROS production. We demonstrate the effective use of AMF associated with P. cretica var. nervosa for Sb phytoremediation and the potential of applying proteomics to better understand the mechanism behind this symbiotic plant physiological response.

Evaluating the metabolic functional profiles of the microbial community and alfalfa (Medicago sativa) traits affected by the presence of carbon nanotubes and antimony in drained and waterlogged sediments

Antimony (Sb) is the ubiquitous re-emerging contaminant greatly accumulated in sediments which has been revealed risky to ecological environment. However, the impacts of Sb (III/V) on microbes and plants in sediments, under different water management with presence of engineering materials are poorly understood. This study conducted sequential incubation of sediments (flooding, draining and planting) with presence of multiwall carbon nanotubes (MWCNTs) and Sb to explore the influence on microbial functional diversity, Sb accumulation and alfalfa traits. Results showed that water management and planting led to greater impacts of sediment enzyme activities and microbial community metabolic function and bioavailable Sb fractions (defined as sum of acid-soluble fraction and reducible fraction, F1 + F2). Available fractions of Sb (V) showed higher correlation to microbial metabolism (r = 0.933) than that of Sb (III) (r = -0.480) in planting stage. MWCNTs with increasing concentrations (0.011%, w/w) positively correlated to microbial community metabolic function in planting stage whereas resulted in decreasing of Sb (III/V) concentrations in alfalfa, although 0.01% MWCNT led to increase of Sb (V) and decrease of Sb (V) by 50.97% and 32.68% respectively. This study provided information for investigating combined ecological impacts of heavy metal and engineering materials under different water managing sediments.

Lead phytoremediation potentials of four aquatic macrophytes under hydroponic cultivation

Lead (Pb) is a major toxicological concern of the present day that demands immediate attention. The use of aquatic macrophytes with high Pb tolerance and accumulation may be a very convenient and economically viable solution for remediating Pb. We examined the ability of Salvinia cucullata, Alternanthera sessilis, Lemna minor, and Pistia stratiotes to remove 0.12 mM, 0.24 mM, 0.36 mM, and 0.48 mM Pb for 96-h under hydroponic cultivation system. The plants accumulated variable amounts of Pb: S. cucullata > A. sessilis > P. stratiotes > L. minor, with low mobility of Pb from root to shoot. Lead uptake kinetics were monitored up to 96-h. After 96-h, the uptake efficiency for S. cucullata (98-99%), A. sessilis (79-96%), L. minor (45-79%), and P. stratiotes (40-76%) was noted. For S. cucullata and A. sessilis, an extremely high uptake rate was seen within the initial 24-h of trials, followed by slower uptake till 96-h. P. stratiotes and L. minor worked best at 0.12 mM Pb. Pb-Phytotoxicity became prominent at 0.48 mM exposure with biomass loss and morphological changes. The plants had a quick growth rate, extensive root system, high biomass yield, and the ability to tolerate and accumulate Pb that made them suitable for phytoremediation purposes. NOVELTY STATEMENT: Lead phytoremediation potential of four aquatic macrophytes found in Indian waters was evaluated. These macrophytes, often considered as weeds, could be used for phytoremediation purposes that would turn out to be a sustainable means of the utilization of natural resources in developing countries like India. In this study, not only metal accumulation by plants but also the lead uptake kinetics at several time intervals and valuable growth attributes were estimated to establish the suitability of these plants as probable lead phytoremediators. Two of the plant species, Salvinia cucullata, and Alternanthera sessilis, showed excellent Pb accumulation capacities that had not been reported earlier, to the best of our knowledge. The work is all the more significant as there have been needs for identifying Pb-phytoremediators well suited to native climate and growth conditions that could take up large amounts of metal from the substratum.

Abiotic mediation of common ions on the co-exposure of CeO2 NPs with Sb (III) or Sb (V) to Glycine max (Linn.) Merrill. (Soybean): Impacts on uptake, accumulation and physiochemical characters

With the most active Sb mines, the "dominance" on Sb production of China lead to increasingly release and omnipresence of Sb in environment through mining activities as well as the life cycle of Sb-containing productions. The introduction of engineered nanoparticles (ENPs) accidentally or intentionally (such as NP-containing sludge as fertilizer) might increase the probability of co-exposed with Sb to plants. In this study, CeO2 NPs, one of the most widely used nanomaterials in industries with potential oxidizing or reducing properties, was selected and co-exposed with Sb (III) or Sb (V) to investigate their mutual effects on uptake, accumulation and physiological effects in soybeans. The results showed that CeO2 NPs increased the Sb (III) and Sb (V) concentrations in roots by 36.7% and 14.0% respectively, while Sb (III) and Sb (V) inhibited the concentration of Ce in roots by 97.1% and 86.9% respectively. In addition, the impacts of extra common ions (Mn2+, Cu2+, Fe3+ and Zn2+) on the fate of Ce and Sb in soybeans in co-exposure of CeO2 NPs with Sb were investigated as well. Mn2+ and Fe3+ increased the accumulations of Ce and Sb (III) in the co-exposure of CeO2 NPs with Sb (III), but reduced that in the co-exposure of CeO2 NPs with Sb (V). Notably, the addition of Cu2+ and Zn2+ consistently increased the uptake and accumulation of Ce and Sb in the co-exposure treatments. Moreover, the effects of Sb on the dissolved portion of CeO2 NPs in soybean roots were also investigated. This study provided a perspective that extra ingredient (mineral elements, organic element or other nutrients) might regulated the interactions in ENPs-heavy metals-plants system which need further explorations.

Toxicity of different forms of antimony to rice plants: Effects on reactive oxidative species production, antioxidative systems, and uptake of essential elements

Antimonite [Sb(III)] and antimonate [Sb(V)] are known to have different toxicity to plants, but the corresponding mechanisms are not fully understood. This study was conducted to investigate reactive oxygen species (ROS), antioxidant systems, and levels of certain essential elements in response to exposure to Sb(III) and Sb(V). Results showed that exposure to Sb(V) caused oxidative stress in a rice plant (Yangdao No.6). Sb(III) was shown to be more toxic than Sb(V) as judged from a lower shoot biomass, a higher loss of essential elements, and higher production of superoxide anion free radicals (O₂^-). The toxicity of Sb(III) might partially be due to the disturbance of the O₂^- dismutation reaction, which resulted in root cell membrane damage under exposure to 20 mg L^-1 Sb(III). Sb(V) stimulated the shoot fresh weight and the shoot uptake of many essential elements. Moreover, Sb(V) and Sb(III) both stimulated the accumulation of calcium in the shoots and roots, and calcium was found to significantly correlate with the concentrations of many essential elements and with some parameters correlated to antioxidant systems, suggesting a Ca-induced regulatory mechanism. The activity of glutathione peroxidase was significantly enhanced by Sb(V) and Sb(III), suggesting a role in scavenging hydrogen peroxide. Catalase was activated by exposure to 20 mg L^-1 Sb(III) in the roots and by exposure to 20 mg L^-1 Sb(V) both in the shoots and roots. However, peroxidase was activated by exposure to 5 mg L^-1 Sb(III) in the shoots and by exposure to 5 mg L^-1 Sb(V) in the roots. This study, for the first time, showed the differences between Sb(V) and Sb(III) toxicity when looking at the antioxidant response and essential element uptake.

Influences of soil properties and long-time aging on phytotoxicity of antimony to barley root elongation

Antimony (Sb) is a toxic element of global concern. To date, the most previous researches about phytotoxicity of Sb failed to fully consider the effects of soil properties and long-time aging. To address this, the toxicity of exogenous Sb(III) and Sb(V) were studied using the standardized barley root elongation bioassay. The results indicated that in ten soils aged only for 1 d, the EC₁₀ (concentrations causing 10% inhibition) values were 221-3164 mg kg^-1 and 135-4260 mg kg^-1 in Sb(III)- and Sb(V)-treated soils, respectively. The EC₅₀ values (concentrations causing 50% inhibition) were more than the setting highest concentration of 6400 mg kg^-1 in half of ten soils. The regression analysis showed that the amorphous Fe oxide and pH were the most foremost single soil factor explaining above-mentioned variance in EC₁₀, respectively, which suggested that the dominant soil factors were related to Sb forms. The inclusion of amorphous Mn oxide in above these two simple regression model could best explain the toxicity variance. After aged for 116 and 365 d, the phytotoxicity of Sb in Sb-treated soils significantly decreased and the phytotoxicity were even not found in the majority of Sb(V)-treated soils. The extent of aging varied with soils, and correlation analysis indicated that the aging effects negatively correlated with soil pH and positively correlated with clay and amorphous Al oxide in the Sb(III)-treated test soils.

Arsenic accumulation and distribution in Pteris vittata fronds of different maturity: Impacts of soil As concentrations

Arsenic (As) hyperaccumulator Pteris vittata is efficient in As uptake, translocation and accumulation, but the impacts of soil As concentrations on As accumulation and distribution in P. vittata are still unclear. The impacts of soil As (7.3, 63 and 228 mg kg^-1) on plant growth and As accumulation in P. vittata after 6 months of growth were evaluated. Arsenic concentrations in the roots, midribs and pinna margin of P. vittata fronds of different maturity were determined by inductively coupled plasma mass spectrometry (ICP-MS) and scanning electron microscopy coupled with an energy dispersive spectrometer (SEM-EDS). While moderate As level at As₆₃ didn't impact P. vittata growth, higher As at As₂₂₈ decreased plant biomass by 38%. Under As stress, more As was accumulated in the senescing fronds (47%) and mature fronds (11%) than the young fronds. In senescing fronds, As concentrations in pinna margin were 2.3 times that of the midribs, consistent with As-induced necrotic symptom. Arsenic distribution based on SEM-EDS analysis revealed good correlation between Si and As in the pinnae (r = 0.49). Our data showed that As accumulation in pinna margin caused necrosis and Si may have a potential role in As detoxification in P. vittata.

Toxicity of different forms of antimony to rice plant: Effects on root exudates, cell wall components, endogenous hormones and antioxidant system

Antimony (Sb) is a toxic element for both human and plants, but the toxic responses of plants to different forms of antimony and the associated mechanisms are unknown. This study was carried out to investigate the effects of different forms of Sb [Sb(III) and Sb(V)] on the root exudates, root endogenous hormones, root cell wall components and antioxidant systems in rice plant via three hydroponic experiments. The results showed that Sb(III) displayed a higher toxicity than Sb(V) to the plant which accumulated much more Sb in its tissues under Sb(III) exposure than that under Sb(V) exposure. Under Sb(III) exposure, most of absorbed Sb was found to be Sb(III) in the shoots and roots; however when plants were exposed to Sb(V), most of absorbed Sb in this rice plant was Sb(V). Only two kinds of endogenous hormones were detected as abscisic acid (ABA) and salicylic acid (SA). The addition of Sb(III) significantly increased the content of ABA but Sb(V) did not, probably suggesting the higher toxicity of Sb(III) than Sb(V) might be due to the stimulation of ABA content. The addition of Sb(III) significantly increased the concentration of oxalic acid but decreased the concentrations of formic, acetic and maleic acids. Sb(V) also enhanced the oxalic acid concentration at 20 mg L^-1 Sb(V) treatment level but reduced the concentrations of formic and acetic acids. Different forms of Sb dose-dependently increased the content of pectin, but significantly enhanced the content of lignin in cell wall. Different forms of Sb induced oxidative stress, but rice plant triggered the activities of superoxide dismutase (SOD) and ascorbate peroxidase (APX) to counteract the oxidative stress.

Pollution Characteristics of Sb, As, Hg, Pb, Cd, and Zn in Soils from Different Zones of Xikuangshan Antimony Mine

Major sources of pollution during the antimony (Sb) mining and processing are mining waste rock, smelting waste, tailings dam, and underground tunnel wastewater. The aim of the present study was to assess magnitude of pollution from Sb mine by taking four types of samples: soil in the mining waste rock zone, soil in the smelting zone, soil in tailings zone, and soil in underground tunnel wastewater zone. Sixty soil samples from the four zones were taken for experimental work, and the contents and morphological characteristics of the six potentially toxic elements (PTEs) such as Sb, As, Hg, Pb, Cd, and Zn in the soil samples were measured by using a hydride generation atomic fluorescence spectrometer (AFS-9700). The results show that the soil of the mine area is seriously polluted. The average contents of Sb, As, Hg, Pb, Cd, and Zn in the soil reach 1267.20 mg·kg^-1, 94.44 mg·kg^-1, 1.46 mg·kg^-1, 184.19 mg·kg^-1, 8.54 mg·kg^-1, and 1054.11 mg·kg^-1, respectively. There exists good correlation between the PTEs in the soil, with Sb strongly positively correlated with As, Hg, Pb, and Zn. The intensity of pollution is highest in the antimony-smelting zone, where the potential ecological risk index is over 15,000, followed by the tailings zone and mining waste rock zone, with the underground tunnel wastewater zone being the lowest. Using sequential chemical extraction, the elements are associated with the residual fraction, followed by organic-sulfide fraction, and smaller portions in the Fe-Mn oxide, carbonate, and exchangeable fractions. There are great differences in the speciation content of different elements in different sampling zones. The study implicates that Sb-smelting zone is the potential source of PTEs and maximum metals are associated with residual phase, out of which significant portion is associated with mobile fraction or phase.

How Plants Handle Trivalent (+3) Elements

Plant development and fitness largely depend on the adequate availability of mineral elements in the soil. Most essential nutrients are available and can be membrane transported either as mono or divalent cations or as mono- or divalent anions. Trivalent cations are highly toxic to membranes, and plants have evolved different mechanisms to handle +3 elements in a safe way. The essential functional role of a few metal ions, with the possibility to gain a trivalent state, mainly resides in the ion's redox activity; examples are iron (Fe) and manganese. Among the required nutrients, the only element with +3 as a unique oxidation state is the non-metal, boron. However, plants also can take up non-essential trivalent elements that occur in biologically relevant concentrations in soils. Examples are, among others, aluminum (Al), chromium (Cr), arsenic (As), and antimony (Sb). Plants have evolved different mechanisms to take up and tolerate these potentially toxic elements. This review considers recent studies describing the transporters, and specific and unspecific channels in different cell compartments and tissues, thereby providing a global vision of trivalent element homeostasis in plants.

Uptake, translocation and phytotoxicity of antimonite in wheat (Triticum aestivum)

Antimony (Sb) contamination of soils and its potential negative impact on crop yields have been recently recognized. To explore the effects of Sb(III) on wheat, responses of physical growth properties, enzyme activities and gene expression were examined. The root length was the most relevant indicator to exposure concentration, the root fresh weight was the most sensitive endpoint according to the comparison of the EC₅₀ (50% inhibitory effect concentration) values, and NRAMP1 gene expression at 1 mg L^-1 was more sensitive than other genes. The genes HMA2 and IRT1 were upregulated but less sensitive than NRAMP1. Additionally, the antioxidant enzyme response was examined to explore Sb toxicity toward wheat. The glutathione (GSH) content in roots exposed to high concentrations of Sb(III) was higher than that in the control group, which indicated that GSH is involved in protecting wheat against the effects of Sb(III). Comparing the different antioxidant responses and correlations with malondialdehyde (MDA) in different tissues, super oxide dismutase (SOD) exhibited the main contribution to defense Sb(III) in roots; SOD and peroxidase (POD) were the major antioxidants in shoots. Gene expression of transporter proteins was a highly sensitive indicator of Sb toxicity in wheat and allowed for understanding the defense mechanism in wheat. The upregulation of HMA2 under Sb(III) expression was one kind of defense mechanism, which can induce efflux of heavy metals into the apoplast or vacuoles. Biomass and plant height results suggested that wheat may grow better than other crops under similar exposure due to the lower degree of Sb uptake. This work is the first to provide a wheat uptake model of Sb(III) under a wide concentration range as well as a perspective on the response to this stress at the molecular level.

Toxicity of exogenous antimony to the soil-dwelling springtail Folsomia candida

Antimony (Sb) is a toxic pollutant, but data for Sb toxicity to springtails in soil are limited, and the effects of Sb speciation, soil physiochemical properties, and aging time on Sb toxicity have not been investigated. To address this, the effects of Sb on Folsomia candida were evaluated in laboratory studies. The results demonstrated that compared with Sb(III), no significant change in mortality was observed in Sb(V)-treated soil, but the EC₅₀ value for the reproduction was 28-fold higher than that of Sb(III). Sb(III) toxicity was very different in four soils. The LC₅₀ values for the survival were 2325-5107 mg kg^-1 in the acute test and 605-2682 mg kg^-1 in the chronic test, and the EC₅₀ values for the reproduction were 293-2317 mg kg^-1. The toxicity discrepancies were associated with the variations in oxidation potential and sorption capacity among corresponding soils. Toxicity significantly positively correlated with the clay and amorphous iron content but significantly negatively correlated with pH. Long-term aging markedly decreased Sb(III) toxicity, and the EC₅₀ and LC₅₀ values were unexpectedly higher than the highest test concentration in soil aged for 180 days. Sb(III) toxicity was probably modified more by oxidation than by changes in the available Sb fraction during aging.

Antimony speciation in the environment: Recent advances in understanding the biogeochemical processes and ecological effects

Antimony (Sb) is a toxic metalloid, and its pollution has become a global environmental problem as a result of its extensive use and corresponding Sb-mining activities. The toxicity and mobility of Sb strongly depend on its chemical speciation. In this review, we summarize the current knowledge on the biogeochemical processes (including emission, distribution, speciation, redox, metabolism and toxicity) that trigger the mobilization and transformation of Sb from pollution sources to the surrounding environment. Natural phenomena such as weathering, biological activity and volcanic activity, together with anthropogenic inputs, are responsible for the emission of Sb into the environment. Sb emitted in the environment can adsorb and undergo redox reactions on organic or inorganic environmental media, thus changing its existing form and exerting toxic effects on the ecosystem. This review is based on a careful and systematic collection of the latest papers during 2010-2017 and our research results, and it illustrates the fate and ecological effects of Sb in the environment.

Effects of Antimony Stress on Photosynthesis and Growth of Acorus calamus

This study was aimed to explore that effects of Sb on physiological parameters of Acorus calamus and the possibility of using A. calamus as a remediation plant. A. calamus potted experiments were conducted using different concentrations (0, 250, 500, 1000, and 2000 mg/kg) of antimony potassium tartrate (Sb3+) (marked as CK, T1, T2, T3, and T4, respectively) and potassium pyroantimonate (Sb5+) (marked as CK, T'1, T'2, T'3, and T'4, respectively). The effects of Sb stress (Sb3+ and Sb5+) on leaf photosynthetic pigments, biomass, photosynthetic characteristics and chlorophyll fluorescence parameters of potted A. calamus were studied. With the rise of Sb3+ concentration from T1 to T4, the leaf pigment contents (chlorophyll a, b, carotenoid), plant height, dry weight, net photosynthetic rate (Pn), stomatal conductance (Gs), evaporation rate (E), PSII maximum photochemical efficiency (Fv/Fm), and PSII electron transfer quantum yield rate (ΦPSII) of A. calamus all reduced, while intercellular CO2 concentration (Ci) significantly increased. The reduction of Pn was mainly induced by non-stomatal limitation. Chlorophyll a/b ratio increased significantly versus the control, while carotenoid/chlorophyll ratio (Car/Chl) first decreased and then increased. The leaf Chl a, Chl b, Car, plant height, dry weight, Pn, Gs, E, Fv/Fm, and ΦPSII all maximized in T'1 (250 mg/kg), but were not significantly different from the control. As the Sb5+ concentration increased from T'2 to T'4, the above indices all decreased and were significantly different from the control. Moreover, intercellular CO2 concentration (Ci) decreased significantly. The reduction of Pn was caused by non-stomatal limitation, indicating the mesophyll cells were damaged. The Car/Chl ratio was stable within 0-500 mg/kg Sb, but decreased in T3 and T4, and rose in T'3 and T'4. After Sb3+ and Sb5+ treatments, translocation factor varied 19.44-27.8 and 19.44-24.86%, respectively. In conclusion, different form Sb3+ treatment, Sb5+ treatment showed a Hormesi effect, as low-concentration treatment promoted A. calamus growth, but high-concentration treatment inhibited its growth. The two forms of Sb both caused unfavorable effects on A. calamus, but the seedlings did not die and were modestly adaptive and Sb-accumulative. A. calamus, which is easily maintained and cultivated, can serve as a good candidate for phytoremediation of water contaminated with Sb.

Fate and chemical speciation of antimony (Sb) during uptake, translocation and storage by rye grass using XANES spectroscopy

Antimony (Sb) is a contaminant of increased prevalence in the environment, but there is little knowledge about the mechanisms of its uptake and translocation within plants. Here, we applied for the synchrotron based X-ray absorption near-edge structure (XANES) spectroscopy to analyze the speciation of Sb in roots and shoots of rye grass (Lolium perenne L. Calibra). Seedlings were grown in nutrient solutions to which either antimonite (Sb(III)), antimonate (Sb(V)) or trimethyl-Sb(V) (TMSb) were added. While exposure to Sb(III) led to around 100 times higher Sb accumulation in the roots than the other two treatments, there was no difference in total Sb in the shoots. Antimony taken up in the Sb(III) treatment was mainly found as Sb-thiol complexes (roots: >76% and shoots: 60%), suggesting detoxification reactions with compounds such as glutathione and phytochelatins. No reduction of accumulated Sb(V) was found in the roots, but half of the translocated Sb was reduced to Sb(III) in the Sb(V) treatment. Antimony accumulated in the TMSb treatment remained in the methylated form in the roots. By synchrotron based XANES spectroscopy, we were able to distinguish the major Sb compounds in plant tissue under different Sb treatments. The results help to understand the translocation and transformation of different Sb species in plants after uptake and provide information for risk assessment of plant growth in Sb contaminated soils.

The Potential Use of Vetiveria zizanioides for the Phytoremediation of Antimony, Arsenic and Their Co-Contamination

Antimony (Sb) and arsenic (As) contaminations are the well reported and alarming issues of various contaminated smelting and mining sites all over the world, especially in China. The present hydroponic study was to assess the capacity of Vetiveria zizanioides for Sb, As and their interactive accumulations. The novelty of the present research is this that the potential of V. zizanioides for Sb and As alone and their interactive accumulation are unaddressed. This is the first report about the interactive co-accumulation of Sb and As in V. zizanioides. Highest applied Sb and As contaminations significantly inhibited the plant growth. Applied Sb and As alone significantly increased their concentrations in the roots/shoot of V. zizanioides. While co-contamination of Sb and As steadily increased their concentrations, in the plant. The co-contamination of Sb and As revealed a positive correlation between the two, as they supplemented the uptake and accumulation of each other. The overall translocation (TF) and bioaccumulation factors (BF) of Sb in V. zizanioides, were 0.75 and 4. While the TF and BF of As in V. zizanioides, were 0.86 and 10. V. zizanioides proved as an effective choice for the phytoremediation and ecosystem restoration of Sb and As contaminated areas.

Effects of antimony on redox activities and antioxidant defence systems in sunflower (Helianthus annuus L.) plants

The alterations induced by the toxicity of antimony (Sb) in the roots and leaves of sunflower plants were determined. The plants were grown hydroponically with different concentrations of Sb, a heavy metal which reduces biomass production and growth. There was preferential accumulation of Sb in the tissues of the roots, with the concentrations in the leaves being much lower. The accumulation of other mineral elements was also altered, especially that of Fe and Zn. Chlorophyll content declined, as also did the photosynthetic efficiency, but the carotenoid content remained unaltered. The total content of phenolics, flavonoids, and phenylpropanoid glycosides rose, evidence of their participation in the defence response. Increases were observed in the amount of superoxide anion in both roots and leaves, and in lipid peroxidation levels, especially with the highest Sb concentration of 1.0 mM. The induced oxidative stress leads to a strong increase in the SOD, POX and APX antioxidant activities, while the GR activity was only increased in the leaves and at the 1.0 mM Sb concentration. In contrast, the DHAR activity increased considerably in both organs. The GSNOR activity increased only in roots, and the total RSNOs increased. The total amount of AsA + DHA increased in roots and remained unaltered in leaves, whereas that of GSH + GSSG decreased considerably in all cases. As a whole, these results are evidence for the development of a strong oxidative stress induced by Sb, with there being a clear imbalance in the content of the compounds that constitute the AsA/GSH cycle. 0.5 mM Sb enhances GST expression, especially in leaves. This, together with the increase that was observed in the amount of GSH, may play an important part in detoxification. This oxidative stress affects both the phenolic and the ROS/RNS metabolic processes, which seems to implicate their involvement in the plant's defence and response to the stress.

Research on the Characteristics and Mechanism of the Cumulative Release of Antimony from an Antimony Smelting Slag Stacking Area under Rainfall Leaching

We aimed to study the characteristics and the mechanism of the cumulative release of antimony at an antimony smelting slag stacking area in southern China. A series of dynamic and static leaching experiments to simulate the effects of rainfall were carried out. The results showed that the release of antimony from smelting slag increased with a decrease in the solid-liquid ratio, and the maximum accumulated release was found to be 42.13 mg Sb/kg waste and 34.26 mg Sb/kg waste with a solid/liquid ratio of 1 : 20; the maximum amount of antimony was released within 149-420 μm size fraction with 7.09 mg/L of the cumulative leaching. Also, the antimony release was the greatest and most rapid at pH 7.0 with the minimum release found at pH 4.0. With an increase in rainfall duration, the antimony release increased. The influence of variation in rainfall intensity on the release of antimony from smelting slag was small.

Interaction of As and Sb in the hyperaccumulator Pteris vittata L.: changes in As and Sb speciation by XANES

Arsenic (As) and antimony (Sb) are chemical analogs that display similar characteristics in the environment. The As hyperaccumulator Pteris vittata L. is a potential As-Sb co-accumulating species. However, when this plant is exposed to different As and Sb speciation, the associated accumulating mechanisms and subsequent assimilation processes of As and Sb remain unclear. A 2-week hydroponic experiment was conducted by exposing P. vittata to single AsIII, AsV, SbIII, and SbV or the co-existence of AsIII and SbIII and AsV and SbV. P. vittata could co-accumulate As and Sb in the pinna (>1000 mg kg(-1)) with high translocation (>1) of As and Sb from the root to the pinna. P. vittata displayed apparent preference to the trivalent speciation of As and Sb than to the pentavalent speciation. Under the single exposure of AsIII or SbIII, the pinna concentration of As and Sb was 84 and 765 % higher than that under the single exposure of AsV or SbV, respectively. Despite the provided As speciation, the main speciation of As in the root was AsV, whereas the main speciation of As in the pinna was AsIII. The Sb in the roots comprised SbV and SbIII when exposed to SbV but was exclusively SbIII when exposed to SbIII. The Sb in the pinna was a mixture of SbV and SbIII regardless of the provided Sb speciation. Compared with the single exposure of As, the co-existence of As and Sb increased the As concentration in the pinna of P. vittata by 50-66 %, accompanied by a significant increase in the AsIII percentage in the root. Compared with the single exposure of Sb, the co-existence of Sb and As also increased the Sb concentration in the pinna by 51-100 %, but no significant change in Sb speciation was found in P. vittata.

Efficient arsenate removal by magnetite-modified water hyacinth biochar

Magnetic biochars (MW) prepared by chemical co-precipitation of Fe(2+)/Fe(3+) on water hyacinth biomass followed by pyrolysis exhibited important potential in aqueous As(V) elimination. In comparison, MW2501 outperformed other MWs and exhibited the highest As(V) sorption capacity which was estimated to be 7.4 mg g(-1) based on Langmuir-Freundlic model. With solution pH ranging from 3 to 10, As(V) removal efficiency by MW2501 kept stable and consistently higher than 90%. Besides, ∼100% removal of 0.5 mM As(V) can be obtained in the presence of P ≤ 0.1 mM or Cr/Sb ≤ 0.5 mM, indicating a wide applicability of MW2501 for treatment of As-containing water. The predominance of Fe3O4 on MW2501 surface was evidenced by XRD. Ligand exchange between As(V) anion and the hydroxylated surface of Fe3O4 as well as H bond was largely responsible for As(V) sorption as suggested by FTIR. XPS analysis further revealed the dominance of As(V) in the sorbed As on MW2501 surface with co-occurrence of a minor proportion of As(III) (11.45%). In parallel, oxidative transformation of Fe3O4 to Fe2O3 was also suggested by XPS. By a lab-scale column test, the potential and suitability of MW2501 in As-containing water treatment was further confirmed, which could also provide an alternative way to manage and utilize this highly problematic invasive species.

Growth, photosynthesis, and defense mechanism of antimony (Sb)-contaminated Boehmeria nivea L

Ramie (Boehmeria nivea L.) is the oldest cash fiber crop in China and is widely grown in antimony (Sb) mining areas. To evaluate the extent of Sb resistance and tolerance, the growth, tolerance index (TI), Sb content in plant parts and in Hoagland solution, bioaccumulation factor (BF), photosynthesis, and physiological changes in Sb-contaminated B. nivea (20, 40, 80, and 200 mg L(-1) Sb) grown hydroponically were investigated. The Sb tolerance and resistance of ramie were clearly revealed by growth inhibition, a TI between 13 and 99 %, non-significant changes in the maximum quantum efficiency of photosystem (F v /F m ), energy-harvesting efficiency (photosystem II (PSII)) and single-photon avalanche diode (SPAD) value, a significant increase in Sb in plant parts, BF >1, and an increase in catalase (CAT) and malondialdehyde (MDA) at 200 mg L(-1) Sb. Under increasing Sb stress, nearly the same non-significant decline in the maximum quantum efficiency of photosystem (F v /F m ), energy-harvesting efficiency (PSII), relative quantum yield of photosystem II (φPSII), and photochemical quenching (qP), except for F v /F m at 20 mg L(-1) Sb, were recorded. SPAD values for chlorophyll under Sb stress showed an increasing trend, except for a slight decrease, i.e., <2 %, than the control SPAD value at 200 mg L(-1) Sb. With a continuous increase in MDA, superoxide dismutase (SOD), peroxidase (POD), and CAT activities were suppressed under Sb addition up to 40 mg L(-1) Sb and the addition of Sb enhanced enzyme production at 80 and 200 mg L(-1) Sb. A continuous decrease in SOD, POD, and CAT up to 40 mg L(-1) Sb and enhancements at ≥80 mg L(-1), along with the continuous enhancement of MDA activity and inhibited biomass production, clearly reveal the roles of these enzymes in detoxifying Sb stress and the defense mechanism of ramie at 80 mg L(-1) Sb. Thus, B. nivea constitutes a promising candidate for Sb phytoremediation at mining sites.

Antimony (SbIII) reduces growth, declines photosynthesis, and modifies leaf tissue anatomy in sunflower (Helianthus annuus L.)

The role of antimony (Sb)--a non-essential trace metalloid--in physiological processes running in crops is still poorly understood. Present paper describes the effect of Sb tartrate (SbIII) on growth, Sb uptake, photosynthesis, photosynthetic pigments, and leaf tissue organization in young sunflower plants grown in hydroponics. We found that growth of below- and aboveground part was reduced with increasing concentration of Sb in the medium. Although Sb was mostly taken up by sunflower roots and only small part (1-2%) was translocated to the shoots, decline in photosynthesis, transpiration, and decreased content of photosynthetic pigments were observed. This indicates that despite relatively low mobility of Sb in root-shoot system, Sb in shoot noticeably modifies physiological status and reduced plant growth. Additionally, leaf anatomical changes indicated that Sb reduced the size of intercellular spaces and made leaf tissue more compact.

Uptake of antimonite and antimonate by arsenic hyperaccumulator Pteris vittata: Effects of chemical analogs and transporter inhibitor

Antimonite (SbIII) is transported into plants via aquaglyceroporin channels but it is unknown in As-hyperaccumulator Ptreis vittata (PV). We tested the effects of SbIII analogs (arsenite-AsIII, glycerol, silicic acid-Si, and, glucose), antimonate (SbV) analog (phosphate-P), and aquaglyceroporin transporter inhibitor (silver, Ag) on the uptake of SbIII or SbV by PV gametophytes. PV gametophytes were grown in 20% Hoagland solution containing 65 μM SbIII or SbV and increasing concentrations of analogs at 65-6500 μM for 2 h or 4 h under sterile condition. After exposing to 65 μM Sb for 2 h, PV accumulated 767 mg/kg Sb in SbIII treatment and 419 mg/kg in SbV treatment. SbIII uptake by PV gametophytes was not impacted by glycerol or AsIII nor aquaglyceroporin inhibitor Ag during 2 h exposure. While Si increased SbIII uptake and glucose decreased SbIII uptake by PV gametophytes, the impact disappeared during 4 h exposure. Under P-sufficient condition, P increased SbIII uptake and decreased SbV uptake during 2 h exposure, but the effect again disappeared after 4 h. After being P-starved for 2 weeks, P decreased SbIII with no effect on SbV uptake during 2 h exposure. Our results indicated that: 1) PV gametophytes could serve as an efficient model to study Sb uptake, and 2) unique SbIII uptake by PV may be related to its trait of As hyperaccumulation.

Antimony bioavailability: knowledge and research perspectives for sustainable agricultures

The increasing interest in urban agriculture highlights the crucial question of crop quality. The main objectives for environmental sustainability are a decrease in chemical inputs, a reduction in the level of pollutants, and an improvement in the soil's biological activity. Among inorganic pollutants emitted by vehicle traffic and some industrial processes in urban areas, antimony (Sb) is observed on a global scale. While this metalloid is known to be potentially toxic, it can transfer from the soil or the atmosphere to plants, and accumulate in their edible parts. Urban agriculture is developing worldwide, and could therefore increasingly expose populations to Sb. The objective of this review was in consequences to gather and interpret actual knowledge of Sb uptake and bioaccumulation by crops, to reveal investigative fields on which to focus. While there is still no legal maximal value for Sb in plants and soils, light has to be shed on its accumulation and the factors affecting it. A relative absence of data exists about the role of soil flora and fauna in the transfer, speciation and compartmentation of Sb in vegetables. Moreover, little information exists on Sb ecotoxicity for terrestrial ecosystems. A human risk assessment has finally been reviewed, with particular focus on Sb bioaccessibility.

Influence of silicon on maize roots exposed to antimony - growth and antioxidative response

Pollution of antimony (Sb) raises a serious environmental problem. Although this non-essential element can be taken up by roots and accumulated in plant tissues in relatively high concentrations, there is still lack of knowledge about the effect of Sb on biochemical and metabolic processes in plants. It was shown that application of silicon (Si) can decrease the toxicity of other heavy metals and toxic elements in various plants. The aim of this study was to assess how Si influences the growth and antioxidative response of young Zea mays L. roots exposed to elevated concentrations of Sb. Antimony reduced the root growth and induced oxidative stress and activated antioxidant defense mechanisms in maize. Silicon addition to Sb treated roots decreased oxidative stress symptoms documented by lower lipid peroxidation, proline accumulation, and decreased activity of antioxidative enzymes (ascorbate peroxidase, EC 1.11.1.11; catalase, EC 1.11.1.6; and guaiacol peroxidase, EC 1.11.1.7). Although neither positive nor negative effect of Si has been observed on root length and biomass, changes in the oxidative response of plants exposed to Sb indicate a possible mitigation role of Si on Sb toxicity in plants.