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The functional similarity between indigenous plant species (IPS) and invasive alien species (IAS) governs the invasion process of successful IAS because IPS and coexisting IAS suffer alike or even same ecological selection pressures. The aggravated condition created by heavy metal pollution (HMP) and drought stress may generate a noticeable impact on the invasive competitiveness and invasion process of IAS possibly via the variations in the functional similarity between IPS and IAS. Consequently, it is necessary to illumine the functional similarity between IPS and IAS under HMP and drought stress to clarify the mechanisms underlying the successful invasion of IAS. This study aims to estimate the functional similarity between IPS Amaranthus tricolor L. and IAS A. retroflexus L. under the condition with the alone and combined effects of HMP with different kinds (e.g., Cu and Pb) and drought stress [simulated by polyethylene glycol-6000 (PEG) solution]. HMP notably declines A. tricolor growth but has no remarkable effect on A. retroflexus growth. A. retroflexus displays a strong competitive intensity than A. tricolor under HMP. Further, HMP makes a greater stress intensity on A. tricolor growth than A. retroflexus growth. Therefore, HMP can accelerate A. retroflexus invasion. A. retroflexus displays a poor competitive intensity under drought stress. Thus, drought stress can hinder A. retroflexus invasion. However, drought stress causes a greater stress intensity on A. tricolor growth than A. retroflexus growth. Thus, the continued drought stress may converse the adverse effects of drought stress on A. retroflexus invasion potentially. The two Amaranthus species tend to diverge functionally under the combined HMP and drought stress. Further, A. retroflexus shows a strong competitive intensity than A. tricolor under the combined HMP and drought stress. Moreover, the combined HMP and drought stress induces a greater stress intensity on A. tricolor growth than A. retroflexus growth. Thus, the combined HMP and drought stress can facilitate A. retroflexus invasion. Meanwhile, the competitiveness for sunlight acquisition and leaf photosynthetic capacity may play a key role in the successful invasion of A. retroflexus under the combined HMP and drought stress., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Soil co-contaminated with cadmium (Cd) and decabromodiphenyl ether (BDE-209) is a widespread environmental problem, especially in electronic waste contaminated surroundings. Accumulation of Cd and BDE-209 in crops has possibly harmful effects on local human health. In order to assess the potential of arbuscular mycorrhizal (AM) fungi and amaranth (Amaranthus hypochondriacus L.) in remediation of soil co-contaminated with Cd and BDE-209, pot trials were performed to investigate interactive effects of AM fungi, Cd and BDE-209 on growth of amaranth, uptake of Cd and BDE-209, distribution of chemical forms of Cd and activities of antioxidant enzymes in shoots and dissipation of BDE-209 in soil. The present results showed that shoot biomass of non-mycorrhizal plants was significantly inhibited by increasing of Cd addition (5-15 mg kg -1 ), but were only slightly declined with BDE-209 addition (5 mg kg -1 ). The interaction of Cd and BDE-209 reduced the proportions of ethanol- and d-H 2 O-extractable Cd in shoots, consequently alleviated Cd toxicity to plants and enhanced root uptake of Cd and BDE-209. Inoculation of AM fungi resulted in significantly greater shoot biomass as well as higher concentrations of Cd and BDE-209 compared with non-mycorrhizal treatment. Moreover, AM fungi played a beneficial role in relieving oxidative stress on amaranth by increasing the activities of dismutase (SOD) and catalase (CAT) in shoots and significantly improved the dissipation of BDE-209 in soil. The present study suggested that combination of AM fungi and amaranth may be a potential option for remediation of Cd and BDE-209 co-contaminated soils., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Inc. All rights reserved.)

To decipher the Cd hyperaccumulation and tolerance mechanisms of plants and increase phytoremediation efficiency, in this study, the physiological effects induced by environmentally relevant concentrations (0, 25 and 200 mg/kg) of Cd were characterized in Amaranthus hypochondriacus (K472) at three growth stages using LC/MS-based metabolomics. Metabolomic analysis identified 31, 29 and 30 significantly differential metabolites (SDMs) in K472 exposed to Cd at the early, intermediate and late stages of vegetative growth, respectively. These SDMs are involved in nine metabolic pathways responsible for antioxidation, osmotic balance regulation, energy supplementation and the promotion of metabolites that participate in phytochelatin (PC) synthesis. K472 at the intermediate stage of vegetative growth had the strongest tolerance to Cd with the combined action of Ala, Asp and Glu metabolism, purine metabolism, Gly, Ser and Thr metabolism and Pro and Arg metabolism. Among these crucial metabolic biomarkers, purine metabolism could be the primary regulatory target for increasing the Cd absorption of K472 for the restoration of Cd-contaminated soil., Competing Interests: Declaration of competing interest None., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Chlorsulfuron has been applied in wheat fields as a recognized herbicide worldwide, yet it was officially banned in China since 2014 for its soil persistence problem. On the basis of our previous research that 5-dimethylamino distinctively accelerated degradation rate in soils, a modified amino moiety ( Ia-c ) and monosubstituted amino group ( Id-e ) were introduced onto the fifth position of the benzene ring in sulfonylurea structures, as well as heterocyclic amino substituents ( If-g ) to seek a suitable soil degradation rate during such an in situ crop rotation system. Referring to the biological data and Sc AHAS inhibition and Sc AHAS docking results, they turned out to be AHAS inhibitors with high potent herbicidal activities. The various influence on soil degradation rate along with crop safety indicated that different substituents on the fifth position have exerted an apparent impact. Their united study of structure-activity-safety-degradation relationship has great potential to provide valuable information for further development of eco-friendly agrochemicals.

Although elevated levels of antimony (Sb) in agricultural soil and plant systems can have harmful effects on human health and ecosystems, little is known about the toxicity of Sb to plants and its mechanism. The assessment of Sb bioavailability is essential for understanding its potential risks and toxicity. In this study, we used pot experiments with two agricultural soil types spiked with Sb to investigate the dose-effect relationship between exposure to Sb and toxic effects (growth and bioaccumulation) on edible amaranth (Amaranthus tricolor Linn.). Soil solution (pore water) and seven single extractants were used to assess the bioavailability of Sb. Different toxic effects of Sb to amaranth cultivated in two types of soils (alkaline and acid soil) were observed. In alkaline soil (chestnut soil, pH 8.39), antimony is more easily absorbed by root and transported to shoot by plants, leading to more adverse effects, than in acid soil (pH 4.91) under the same exposure level. Our findings also highlight the need for more attention on asymptomatic accumulation of Sb in plants, especially for agricultural products cultivated in contaminated areas. The extraction efficiency of Sb was various in different extractants and soil types, Mehlich 3, NaHCO 3 and Na 2 HPO 4 for Sb were more efficient than other extractants in both tested alkaline and acid soil. Based on the extractability and correlation coefficients of toxic effects on amaranth and extractable Sb, we found that 0.1 M Na 2 HPO 4 is the best extractant to predict the bioavailability of Sb in soil, and M3 is a suitable alternative. Antimony concentration in soil solution can also be used as an alternative indicator of the bioavailability of Sb., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Phytochelatins (PCs) play a vital role in the tolerance and enrichment of cadmium (Cd) in higher plants by chelating with Cd 2+ . The aim of this study was to perform a full-scale metabolomics analysis of metabolic responses highly correlated with PCs generation. These metabolites and metabolic pathways were expected to promote PCs generation and further optimize Cd absorption in plants. In the current study, Amaranthus hypochondriacus, a potential species for phytoremediation, was first adopted to investigate physiological responses to Cd stress via LCMS/MS-based metabolomics and the HPLC based determination of thiol compounds. The results showed that the leaves of A. hypochondriacus under high Cd stress accumulated 40 times the amount of Cd compared to the leaves of the plants not under Cd stress and had an increased content of three types of PCs. Metabolomics qualitatively identified 12084 substances in total, among which 41 were significantly different metabolites (SDMs) between the two groups and involved in 7 metabolic pathways. Among the SDMs, 12 metabolites were highly linearly correlated with PCs involved in three pathways (Val, Leu and Ile biosynthesis; Ala, Asp and Glu metabolism; and Arg and Pro metabolism). These results provide an innovative method to promote PCs synthesis for the restoration of Cd-contaminated-soil., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Dissolved humic acid (DHA) from soil can interact with multi-walled carbon nanotubes (MWCNTs) and magnetic-modified multi-walled carbon nanotubes (MMWCNTs), and subsequently alter the toxicity of MWCNTs and MMWCNTs to amaranth. This is the first study to compare the effects of MWCNTs and MMWCNTs under natural DHAs on their toxicity to amaranth. When DHAs were combined with 0.5 g/L MWCNTs, 1:2:1 MMWCNTs and 4:2:1 MMWCNTs nanomaterials, DHA 1 and DHA 4 both increased the pH of Hoagland's solutions. DHA 1 more severely decreased the soluble protein levels in shoots than DHA 4 in the 1:2:1 MMWCNT and 4:2:1 MMWCNT treatments. DHA 1 and DHA 4 both increased the chlorophyll concentrations of amaranth treated with MWCNTs, decreased the chlorophyll concentrations in the MMWCNT treatments. Co-exposure of DHAs and carbon-based CNTs caused further decreases in the anthocyanin level as compared to the respective CNT alone treatment. In the nanomaterial alone treatment, both 0.25 and 4:2:1 MMWCNTs greatly lowered the anthocyanin level as compared to the other two CNTs with the same exposure dose. Transmission electron microscopy images showed that the interaction between 4:2:1 MMWCNT and DHA 4 had more serious effects on plant cells across all the treatments., (Copyright © 2018 Elsevier Inc. All rights reserved.)

The accumulation and metabolism of 2, 2', 4, 4', 5, 5'-hexabrominated diphenyl ether (BDE-153) in Amaranthus mangostanus L. (amaranth) as affected by different concentrations of biochar (1.3 to 26.6 g/L) under hydroponic conditions exposed to 10 μg/L BDE-153 after 10 days were investigated. Biochar significantly reduced BDE-153 shoot and root content by 27.5-61.6% and 73-95.3%, respectively. In general, BDE-153 migration from solution to amaranth decreased with increasing the doses of biochar. BDE-153 metabolites altered with doses of biochar. The ratio of de-BDEs to BDE-153 in root was polynomial correlated to biochar dose (R 2  = 0.9356**). Root and shoot Fe content was positively correlated with the BDE-153 amounts (R 2  = 0.948** and 0.822*, respectively). Though the higher biochar dose could obviously control BDE-153 uptake by the vegetable, the toxicity was caused more significantly. For instances, the high concentration of biochar at 26.6 g/L reduced pigment content, increased total ROS, and elevated antioxidant enzyme activity. At the same time, the O 2 - intensity was linearly positively correlated with de-BDEs in root (R 2  = 0.7324*) while photosynthetic parameter F v /fm intensity was polynomial correlated to BDEs in shoot (R 2  = 0.9366*). Transmission electron microscopy (TEM) confirmed that exposure to BDE-153 and high concentration biochar at 26.6 g/L severely altered the chloroplasts in terms of the organelle shape and the presence of starch granules in the chloroplast. Taken together, biochar as a soil amendment could significantly control BDE-153 uptake and enhance BDE-153 metabolism in vegetables, but considering the dose of biochar to avoid its toxicity with higher dose., (Copyright © 2018 Elsevier B.V. All rights reserved.)

In this study, pot experiments were carried out to investigative the effects of growth-promoting hormone diethyl aminoethyl hexanoate (DA-6), 6-Benzylaminopurine (6-BA), and chelator [S,S]-Ethylenediaminedisuccinic acid (EDDS) when applied to soil contaminated with cadmium (Cd). The substances were applied alone and in combination to assess their impact on biomass, Cd phytoextraction, subcellular distribution, and chemical forms in Cd hyperaccumulator Amaranthus hybridus Linn. (A. hybridus). Results showed that the treatment of EDDS alone inhibited plant growth, and raised the Cd concentration in the plant shoot and root. Treatments with DA-6 and 6-BA combined with EDDS alleviated the negative effect of EDDS on plant growth, resulting in a synergistic effect on Cd phytoaccumulation and translocation. At the subcellular level, DA-6 and 6-BA detoxified the Cd toxicity in the plant by retaining the Cd in the cell wall. On the distribution of the chemical form of Cd in plant shoot, DA-6 and 6-BA significantly decreased Cd mobility in the plant compared to EDDS. These results confirmed that combining DA-6 and 6-BA with EDDS can counteract the adverse effect of EDDS on plant growth. The treatment of 5.0 mmol kg -1 EDDS + 1 μM DA-6 was optimal for improving the remediation of A. hybridus Linn. growing in Cd contaminated soil.

Lead (Pb) stress adversely affects in planta nutrient homeostasis and metabolism when present at elevated concentration in the surrounding media. The present study was aimed at investigation of organic acid exudations, elemental contents, growth, and lipid peroxidation in two wild plants (Amaranthus viridis L. and Portulaca oleracea L.), exhibiting differential root to shoot Pb translocation, under Pb stress. Plants were placed in soil spiked with lead chloride (PbCl 2 ) concentrations of 0, 15, 30, 45, or 60 mg Pb/kg soil, in rhizoboxes supplied with nylon nets around the roots. The plant mucilage taken from root surfaces, mirroring the rhizospheric solution, was analyzed for various organic acids. Lead stress resulted in a release of basified root exudates from both plants. Exudates of P. oleracea roots showed a higher pH. In both plants, the pH rising effect was diminished at the highest Pb treatment level. The exudation of citric acid, glutamic acid (in both plants), and fumaric acid (in P. oleracea only) was significantly increased with applied Pb levels. In both plant species, root and shoot Pb contents increased while nutrients (Ca, Mg, and K) decreased with increasing Pb treatment levels, predominantly in A. viridis. At 60 mg Pb/kg soil, shoot Na content of A. viridis was significantly higher as compared to untreated control. Higher Pb treatment levels decreased plant fresh and dry masses as well as the quantity of photosynthetic pigments due to enhanced levels of plant H 2 O 2 and thiobarbituric acid reactive substances in both species. Photosynthetic, growth, and oxidative stress parameters were grouped into three distinct dendrogram sections depending on their similarities under Pb stress. A positive correlation was identified between Pb contents of studied plants and secretion of different organic acids. It is concluded that Pb stress significantly impaired the growth of A. viridis and P. oleracea as a result of nutritional ion imbalance, and the response was cultivar-specific and dependent on exogenous applied Pb levels. Differential lipid oxidation, uptake of nutrients (Ca, Mg, and K) and exudation of citric acid, fumaric acid, and glutamic acid could serve as suitable physiological indicators for adaptations of P. oleracea to Pb enriched environment. The findings may help in devising strategies for Pb stabilization to soil colloids.

Industrial slag from steelwork activities is considered a by-product by the EU legislation and it can be used for civil construction. In this work, an experiment in a greenhouse was conducted over a 6-week period to investigate the effect of soil enrichment with ladle furnace slag on morpho-physiological parameters of Amaranthus paniculatus L. plants. Results showed that the addition of 5% (w/w) slag to soil did not alter the plant growth, highlighting a high tolerance to this slag concentration. Contrarily, plants cultivated in a soil with 10% (w/w) slag showed a marked reduction both in growth and biometric parameters. Moreover, plants grown on a slag-rich soil (20% w/w) highlighted a very low survival rate. This behaviour was confirmed by the biochemical and physiological investigations on chlorophyll a and b content, gas exchange and chlorophyll fluorescence analyses. Metal(loid)s determination showed the accumulation of Ni, Se, Sn, As, Sb and Cd in 10% slag-treated plants, while revealed an increase in Ni, Cd, As and Pb in 5% slag-treated plants. Results are discussed highlighting the profitability of the cultivation of Amaranthus plants on slag enriched soil, as this plant species is largely used both as feedstock for energy production and for environmental restoration., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Among metals, Ni has been indicated as one of the most dangerous for the environment, and plants exposed to this metal are frequently reported to undergo a severe stress condition. In this work, the tolerance responses to different Ni concentrations at physiological and biochemical levels were evaluated in Amaranthus paniculatus L., a plant species previously characterised for their ability to phytoremove Ni from metal-spiked water. Results indicated a good metal tolerance of this plant species at environmentally relevant Ni concentrations, while clear symptoms of oxidative damages were detected at higher Ni concentrations, both in roots and leaves, by measuring lipid peroxide content. At the photosynthetic level, pigment content determination, chlorophyll fluorescence image analysis and gas-exchange parameter measurements revealed a progressive impairment of the photosynthetic machinery at increasing Ni concentrations in the solution. Regarding biochemical mechanisms involved in antioxidative defence and metal binding, antioxidative enzyme (ascorbate peroxidase, APX; catalase, CAT; guaiacol peroxidase, GPX; superoxide dismutase, SOD) activity, polyamine (PA) content, polyamine oxidase (PAO) activity and organic acid (OA) content were differently affected by Ni concentration in the growth solution. A role for GPX, SOD, PAs, and oxalic and citric acid in Ni detoxification is suggested. These results can contribute to elucidate the tolerance mechanisms carried out by plants when facing environmentally relevant Ni concentrations and to identify some traits characterising the physiological and biochemical responses of Amaranthus plants to the presence and bioaccumulation of Ni.

The effects of several silicates (talcum powder (TP), calcium silicate (CS), sodium silicate (SS), and potassium silicate (PS)), in comparison with other amendments (quicklime (QL) and potassium dihydrogen phosphate (PDP)) on cadmium (Cd) uptake by three dicotyledonous crops (Amaranthus hypochondriacus L. Cv. 'K112', Amaranthus tricolor L., and Brassica oleracea var. albiflora Kuntze) were investigated in Cd-contaminated soil. The effects of both application methods of amendments (singly and combined) and timing of application were also evaluated. Sodium silicate was the most effective in reducing crop Cd uptake and translocation, which was diminished by 51% in roots, 53% in stems, and 72% in leaves on average. Application of CS amendment showed greater efficiency than PDP amendment in decreasing Cd uptake by crops and resulted in increased biomass. Potassium silicate only slightly decreased shoot Cd concentration. Combination of PDP and SS was able to overcome the inhibitory effect of SS on crop yield while decreasing Cd concentrations in roots, stems and leaves of the tested crops by average rates of 52, 65, and 68% respectively. Applications of SS and PS significantly reduced the root-to-shoot Cd transfer factor. We found that Si accumulation in crops was not associated with lower Cd concentration, indicating that Si in crops may play a major role in alleviating metal stress rather than inhibiting crop Cd accumulation. We suggested that the inhibitive effect of silicates on crops Cd uptake was majorly attributed to the properties of the silicates, those were their specific effects on soil pH and cations, which increased Cd adsorption by soil and suppressed Cd uptake from soil solution by increasing the relative dissolved concentrations of competing cations.

In a greenhouse pot experiment, we assessed the phytoextraction potential for Cd of three amaranth cultivars (Amaranthus hypochondriacus L. Cvs. K112, R104, and K472) and the effect of application of N, NP, and NPK fertilizer on Cd uptake of the three cultivars from soil contaminated with 5 mg kg(-1) Cd. All three amaranth cultivars had high levels of Cd concentration in their tissues, which ranged from 95.1 to 179.1 mg kg(-1) in leaves, 58.9 to 95.4 mg kg(-1) in stems, and 62.4 to 107.2 mg kg(-1) in roots, resulting in average bioaccumulation factors ranging from 17.7 to 29.7. Application of N, NP, or NPK fertilizers usually increased Cd content in leaves but decreased Cd content in stem and root. Fertilizers of N or NP combined did not substantially increase dry biomass of the 3 cultivars, leading to a limited increment of Cd accumulation. NPK fertilizer greatly increased dry biomass, by a factor of 2.7-3.8, resulting in a large increment of Cd accumulation. Amaranth cultivars (K112, R104, and K472) have great potential in phytoextraction of Cd contaminated soil. They have the merits of high Cd content in tissues, high biomass, easy cultivation and little effect on Cd uptake by fertilization.

When manures from intensive livestock operations are applied to agricultural or vegetable fields at a high rate, large amounts of salts and metals will be introduced into soils. Using a column leaching experiment, this study assessed the leaching potential of the downward movement of Cu and Zn as well as some salt ions after an intensive farm pig manure at rates of 0%, 5% and 10% (w/w) were applied to the top 20 cm of two different textured soils (G soil -sandy loam soil; H soil-silty clay loam soil), and investigated the growth of amaranth and Cu and Zn transfer from soil to amaranth (Amaranthus tricolor). Soil solutions were obtained at 20, 40 and 60 cm depth of the packed column and analyzed for pH, electrical conductivity (EC), dissolved organic matter (DOC) and Cu and Zn concentrations. The results indicated that application of pig manure containing Cu and Zn to sandy loam soil might cause higher leaching and uptake risk than silty clay loam soil, especially at high application rates. And manure amendment at 5% and 10% significantly decreased the biomass of amaranth, in which the salt impact rather than Cu and Zn toxicity from manures played more important role in amaranth growth. Thus the farmer should avoid application the high rate of pig manure containing metal and salt to soil at a time, especially in sandy soil.