Phytoremediation of heavy metals by Alternanthera bettzickiana: Growth and physiological response

Phytobial remediation advances and application of omics and artificial intelligence: a review

Industrialization and urbanization increased the use of chemicals in agriculture, vehicular emissions, etc., and spoiled all environmental sectors. It causes various problems among living beings at multiple levels and concentrations. Phytoremediation and microbial association are emerging as a potential method for removing heavy metals and other contaminants from soil. The treatment uses plant physiology and metabolism to remove or clean up various soil contaminants efficiently. In recent years, omics and artificial intelligence have been seen as powerful techniques for phytobial remediation. Recently, AI and modeling are used to analyze large data generated by omics technologies. Machine learning algorithms can be used to develop predictive models that can help guide the selection of the most appropriate plant and plant growth-promoting rhizobacteria combination that is most effective at remediation. In this review, emphasis is given to the phytoremediation techniques being explored worldwide in soil contamination.

Unravelling the halophyte Suaeda maritima as an efficient candidate for phytostabilization of cadmium and lead: Implications from physiological, ionomic, and metabolomic responses

Cadmium (Cd) and lead (Pb) are among the most toxic heavy metals affecting human health and crop yield. Suaeda maritima (L.) Dumort is an obligate halophyte that is well adapted to saline soil. The inbuilt salinity tolerance mechanisms of halophytes help them to survive in heavy metal-contaminated rhizospheric soil. In the present study, growth and ionomic responses, reactive oxygen species (ROS) accumulation, modulations of phytochelatins, antioxidative defense, and metabolomic responses were studied in S. maritima imposed to Cd and Pb stresses with an aim to elucidate Cd and Pb tolerance mechanisms and phytoremediation potential of this halophyte. Our results showed a reduction of biomass in S. maritima, which may serve as an energy conservation strategy for survival under heavy metal stress. The increased accumulation of ROS with concomitant higher expression of various antioxidative enzymes suggests the efficient scavenging of ROS. The metabolite profiling revealed significant up-regulation of sugars, sugar alcohols, amino acids, polyphenols, and organic acids under Cd and Pb stresses suggesting their possible role in osmotic balance, ionic homeostasis, ROS scavenging, and signal transduction for stress tolerance. In S. maritima, the translocation factors (Tf) are <1 in both Cd and Pb treatments, which indicates that this halophyte has high phytostabilization potential for Cd and Pb in roots and through restricted translocation of heavy metal ions to the aboveground part. The findings of this study offer comprehensive information on Cd and Pb tolerance mechanisms in S. maritima and suggest that this halophyte can detoxify the HMs through physiological, ionic, antioxidative, and metabolic regulations.

Impact of Heavy Metals on Cold Acclimation of Salix viminalis Roots

In nature, plants are exposed to a range of climatic conditions. Those negatively impacting plant growth and survival are called abiotic stresses. Although abiotic stresses have been extensively studied separately, little is known about their interactions. Here, we investigate the impact of long-term mild metal exposure on the cold acclimation of Salix viminalis roots using physiological, transcriptomic, and proteomic approaches. We found that, while metal exposure significantly affected plant morphology and physiology, it did not impede cold acclimation. Cold acclimation alone increased glutathione content and glutathione reductase activity. It also resulted in the increase in transcripts and proteins belonging to the heat-shock proteins and related to the energy metabolism. Exposure to metals decreased antioxidant capacity but increased catalase and superoxide dismutase activity. It also resulted in the overexpression of transcripts and proteins related to metal homeostasis, protein folding, and the antioxidant machinery. The simultaneous exposure to both stressors resulted in effects that were not the simple addition of the effects of both stressors taken separately. At the antioxidant level, the response to both stressors was like the response to metals alone. While this should have led to a reduction of frost tolerance, this was not observed. The impact of the simultaneous exposure to metals and cold acclimation on the transcriptome was unique, while at the proteomic level the cold acclimation component seemed to be dominant. Some genes and proteins displayed positive interaction patterns. These genes and proteins were related to the mitigation and reparation of oxidative damage, sugar catabolism, and the production of lignans, trehalose, and raffinose. Interestingly, none of these genes and proteins belonged to the traditional ROS homeostasis system. These results highlight the importance of the under-studied role of lignans and the ROS damage repair and removal system in plants simultaneously exposed to multiple stressors.

Leptolyngbya sp. XZMQ and Bacillus XZM co-inoculation reduced sunflower arsenic toxicity by regulating rhizosphere microbial structure and enzyme activity

Microorganisms are of great significance for arsenic (As) toxicity amelioration in plants as soil fertility is directly affected by microbes. In this study, we innovatively explored the effects of indigenous cyanobacteria (Leptolyngbya sp. XZMQ) and plant growth-promoting bacteria (PGPB) (Bacillus XZM) on the growth and As absorption of sunflower plants from As-contaminated soil. Results showed that single inoculation and co-inoculation stimulated the growth of sunflower plants (Helianthus annuus L.), enhanced enzyme activities, and reduced As contents. In comparison to the control group, single innoculation of microalgae and bacteria in the rhizosphere increased extracellular polymeric substances (EPS) by 21.99% and 14.36%, respectively, whereas co-inoculation increased them by 35%. Compared with the non-inoculated group, As concentration in the roots, stems and leaves of sunflower plants decreased by 38%, 70% and 41%, respectively, under co-inoculation conditions. Inoculation of Leptolyngbya sp. XZMQ significantly increased the abundance of nifH in soil, while co-inoculation of cyanobacteria and Bacillus XZM significantly increased the abundance of cbbL, indicating that the coupling of Leptolyngbya sp. XZMQ and Bacillus XZM could stimulate the activity of nitrogen-fixing and carbon-fixing microorganisms and increased soil fertility. Moreover, this co-inoculation increased the enzyme activities (catalase, sucrase, urease) in the rhizosphere soil of sunflower and reduced the toxic effect of As on plant. Among these, the activities of catalase, peroxidase, and superoxide dismutase decreased. Meanwhile, co-inoculation enables cyanobacteria and bacteria to attach and entangle in the root area of the plant and develop as symbiotic association, which reduced As toxicity. Co-inoculation increased the abundance of aioA, arrA, arsC, and arsM genes in soil, especially the abundance of microorganisms with aioA and arsM, which reduced the mobility and bioavailability of As in soil, hence, reduced the absorption of As by plants. This study provides a theoretical basis for soil microbial remediation in mining areas.

Chelate facilitated phytoextraction of Pb, Cd, and Zn from a lead-zinc mine contaminated soil by three accumulator plants

This study aims to evaluate the enhancement of phytoextraction of heavy metals (Pb, Cd, and Zn) by species Marrubium cuneatum, Stipa arabica, and Verbascum speciosum, through EDTA amendment. Assisted phytoextraction pot experiments were performed at different EDTA dosages (0, 1, 3, and 5 mmol kg-1 soil). The DTPA-extractable metal content increased in the presence of EDTA, followed by their contents in the tissues of all three studied species. Resulting from oxidative stress, the activity of antioxidant enzymes such as glutathione peroxidase (GPX), superoxide dismutase (SOD), and catalase (CAT) increased when the chelating agent was added. EDTA in higher doses partially decreased chlorophyll concentration, and 5 mmol kg-1 of that reduced the biomass of the studied species. The bioconcentration factor (BCF) for Cd was notably high in all studied plants and considerably elevated for Zn and Pb with the addition of EDTA in M. cuneatum and S. arabica (BCF > 1), whilst an accumulation factor greater than one (AF > 1) was found for Cd in all species and for Pb in the case of S. arabica. In general, the results demonstrated that EDTA can be an effective amendment for phytoextraction of Cd, Zn, and Pb by M. cuneatum, V. speciosum and S. arabica in contaminated soils.

Integrated physiological and omics analyses reveal the mechanism of beneficial fungal Trichoderma sp. alleviating cadmium toxicity in tobacco (Nicotiana tabacum L.)

Cadmium (Cd) is a highly toxic heavy metal and readily accumulates in tobacco, which imperils public health via Cd exposure from smoking. Beneficial microbes have a pivotal role in promoting plant growth, especially under environmental stresses such as heavy metal stresses. In this study, we introduced a novel fungal strain Trichoderma nigricans T32781, and investigated its capacity to alleviate Cd-induced stress in tobacco plants through comprehensive physiological and omics analyses. Our findings revealed that T32781 inoculation in soil leads to a substantial reduction in Cd-induced growth inhibition. This was evidenced by increased plant height, enhanced biomass accumulation, and improved photosynthesis, as indicated by higher values of key photosynthetic parameters, including the maximum quantum yield of photosystem Ⅱ (Fv/Fm), stomatal conductance (Gs), photosynthetic rate (Pn) and transpiration rate (Tr). Furthermore, element analysis demonstrated that T. nigricans T32781 inoculation resulted in a remarkable reduction of Cd uptake by 62.2% and a 37.8% decrease in available soil Cd compared to Cd-stressed plants without inoculation. The protective role of T32781 extended to mitigating Cd-induced oxidative stress by improving antioxidant enzyme activities of superoxide dismutase (SOD), peroxidase (POD), and ascorbate peroxidase (APX). Metabolic profiling of tobacco roots identified 43 key metabolites, with notable contributions from compounds like nicotinic acid, succinic acid, and fumaric acid in reducing Cd toxicity in T32781-inoculated plants. Additionally, rhizosphere microbiome analysis highlighted the promotion of beneficial microbes, including Gemmatimonas and Sphingomonas, by T32781 inoculation, which potentially contributed to the restoration of plant growth under Cd exposure. In summary, our study demonstrated that T. nigricans T32781 effectively alleviated Cd stress in tobacco plants by reducing Cd uptake, alleviating Cd-induced oxidative stress, influencing plant metabolite and modulating the microbial composition in the rhizosphere. These findings offer a novel perspective and a promising candidate strain for enhancing Cd tolerance and prohibiting its accumulation in plants to reduce health risks associated with exposure to Cd-contaminated plants.

Recent progress on emerging technologies for trace elements-contaminated soil remediation

Abiotic stresses from potentially toxic elements (PTEs) have devastating impacts on health and survival of all living organisms, including humans, animals, plants, and microorganisms. Moreover, because of the rapid growing industrial activities together with the natural processes, soil contamination with PTEs has pronounced, which required an emergent intervention. In fact, several chemical and physical techniques have been employed to overcome the negative impacts of PTEs. However, these techniques have numerous drawback and their acceptance are usually poor as they are high cost, usually ineffectiveness and take longer time. In this context, bioremediation has emerged as a promising approach for reclaiming PTEs-contaminated soils through biological process using bacteria, fungus and plants solely or in combination. Here, we comprehensively reviews and critically discusses the processes by which microorganisms and hyperaccumulator plants extract, volatilize, stabilize or detoxify PTEs in soils. We also established a multi-technology repair strategy through the combination of different strategies, such as the application of biochar, compost, animal minure and stabilized digestate for stimulation of PTE remediation by hyperaccumulators plants species. The possible use of remote sensing of soil in conjunction with geographic information system (GIS) integration for improving soil bio-remediation of PTEs was discussed. By synergistically combining these innovative strategies, the present review will open very novel way for cleaning up PTEs-contaminated soils.

The physiology of drought stress in two grapevine cultivars: Photosynthesis, antioxidant system, and osmotic regulation responses

Drought stress impedes viticultural plant growth and development by modifying various metabolic pathways. However, the regulatory network response underlying drought stress is not yet clear. In this study, the leaves and roots of "Shine Muscat" ("SM," Vitis labruscana × Vitis vinifera) and "Thompson Seedless" ("TS," V. vinifera L. cv.) were subjected to drought stress to study the regulatory network used by drought stress. Morphophysiological results showed that the malondialdehyde content after 28 days of drought stress increased more significantly in "TS" than "SM." Furthermore, the multiomics analysis studies showed that a total of 3036-6714 differentially expressed genes and 379-385 differentially abundant metabolites were identified in "SM" and "TS" grapevine cultivars under drought stress. Furthermore, the retained intron was the major form of differential alternative splicing event under drought stress. The photosynthesis pathway, antioxidant system, plant hormone signal transduction, and osmotic adjustment were the primary response systems in the two grapevine cultivars under drought stress. We have identified GRIK1, RFS2, and LKR/SDH as the hub genes in the coexpression network of drought stress. In addition, the difference in the accumulation of pheophorbide-a reveals different drought resistance mechanisms in the two grapevine cultivars. Our study explained the difference in drought response between cultivars and tissues and identified drought stress-responsive genes, which provides reference data for further understanding the regulatory network of drought tolerance in grapevine.

Phytoremediation of cadmium-trichlorfon co-contaminated water by Indian mustard (Brassica juncea): growth and physiological responses

In this study, the morphological and physiological responses of Brassica juncea to the stresses of Cadmium (Cd) and trichlorfon (TCF), and the phytoremediation potential of B. juncea to Cd and TCF were investigated under hydroponics. Results showed that Cd exhibited strong inhibition on biomass and root morphology of B. juncea as Cd concentration increased. The chlorophyll a fluorescence intensity and chlorophyll content of B. juncea decreased with the increased Cd concentration, whereas the malondialdehyde and soluble protein contents and superoxide dismutase activity increased. TCF with different concentrations showed no significant influence on these morphological and physiological features of B. juncea. The biomass and physiological status of B. juncea were predominantly regulated by Cd level under the co-exposure of Cd and TCF. B. juncea could accumulate Cd in different plant parts, as well as showed efficient TCF degradation performance. A mutual inhibitory removal of Cd and TCF was observed under their co-system. The present study clearly signified the physiological responses and phytoremediation potential of B. juncea toward Cd and TCF, and these results suggest that B. juncea can be used as an effective phytoremediation agent for the Cd-TCF co-contamination in water.

Functional characterization of a DNA-damage repair/tolerance 100 (DRT100) gene in Sedum alfredii Hance for genome stability maintenance and Cd hypertolerance

Cd contamination is a world-wild concern for its toxicity and accumulation in food chain. Sedum alfredii Hance (Crassulaceae) is a zinc (Zn) and cadmium (Cd) hyperaccumulator native to China and widely applied for the phytoremediation at Zn or Cd contaminated sites. Although many studies report the uptake, translocation and storage of Cd in S. alfredii Hance, limited information is known about the genes and underlying mechanisms of genome stability maintenance under Cd stress. In this study, a gene resembling DNA-damage repair/toleration 100 (DRT100) was Cd inducible and designated as SaDRT100. Heterologous expression of SaDRT100 gene in yeasts and Arabidopsis thaliana enhanced Cd tolerance capability. Under Cd stress, transgenic Arabidopsis with SaDRT100 gene exhibited lower levels of reactive oxygen species (ROS), fewer Cd uptake in roots and less Cd-induced DNA damage. Evidenced by the subcellular location in cellular nucleus and expression in aerial parts, we suggested the involvement of SaDRT100 in combating Cd-induced DNA damage. Our findings firstly uncovered the roles of SaDRT100 gene in Cd hypertolerance and genome stability maintenance in S. alfredii Hance. The potential functions of DNA protection make SaDRT100 gene a candidate in genetic engineering for phytoremediation at multi-component contaminated sites.

Assessment of the capability of cadmium accumulation and translocation among 31 willows: four patterns of willow biomass variation response to cadmium

Cadmium (Cd) pollution threatens food security and the environment. Willow species (Salix, Salicaceae) exhibit a remarkable potential to restore Cd-polluted sites due to their high biomass production and high Cd accumulation capacities. This study examined the Cd accumulation and tolerance in 31 genotypes of shrub willow in hydroponic conditions at varying Cd levels (0 μM Cd, 5 μM Cd, and 20 μM Cd). The root, stem, and leaf biomass of 31 shrub willow genotypes showed significant differences to Cd exposure. Among 31 willow genotypes, four patterns of biomass variation response to Cd were identified: insensitive to Cd; growth inhibition due to excessive Cd supply (high Cd inhibition); low Cd causing inhibited growth, whereas high Cd leading to increased biomass (U-shape); and growth increment with excessive Cd exposure (high Cd induction). The genotypes belonging to the "insensitive to Cd" and/or "high Cd induction" were candidates for the utilization of phytoremediation. Based on the analysis of Cd accumulation of 31 shrub willow genotypes at high and low Cd levels, genotypes 2372, 51-3, and 1052 obtained from a cross between S. albertii and S. argyracea grew well and accumulated relatively more Cd levels than other genotypes. In addition, for Cd-treated seedlings, root Cd accumulation was positively correlated with shoot Cd accumulation and total Cd uptake, demonstrating that Cd accumulation in roots could serve as a biomarker for evaluating the Cd extraction capacity of willows, especially in hydroponics screening. The results of this study screened out willow genotypes with high Cd uptake and translocation capacities, which will provide valuable approaches for restoring Cd-contaminated soils with willows.

Toxic effects of cadmium on the physiological and biochemical attributes of plants, and phytoremediation strategies: A review

Anthropogenic activities pose a more significant threat to the environment than natural phenomena by contaminating the environment with heavy metals. Cadmium (Cd), a highly poisonous heavy metal, has a protracted biological half-life and threatens food safety. Plant roots absorb Cd due to its high bioavailability through apoplastic and symplastic pathways and translocate it to shoots through the xylem with the help of transporters and then to the edible parts via the phloem. The uptake and accumulation of Cd in plants pose deleterious effects on plant physiological and biochemical processes, which alter the morphology of vegetative and reproductive parts. In vegetative parts, Cd stunts root and shoot growth, photosynthetic activities, stomatal conductance, and overall plant biomass. Plants' male reproductive parts are more prone to Cd toxicity than female reproductive parts, ultimately affecting their grain/fruit production and survival. To alleviate/avoid/tolerate Cd toxicity, plants activate several defense mechanisms, including enzymatic and non-enzymatic antioxidants, Cd-tolerant gene up-regulations, and phytohormonal secretion. Additionally, plants tolerate Cd through chelating and sequestering as part of the intracellular defensive mechanism with the help of phytochelatins and metallothionein proteins, which help mitigate the harmful effects of Cd. The knowledge on the impact of Cd on plant vegetative and reproductive parts and the plants' physiological and biochemical responses can help selection of the most effective Cd-mitigating/avoiding/tolerating strategy to manage Cd toxicity in plants.

Heavy Metals, Their Phytotoxicity, and the Role of Phenolic Antioxidants in Plant Stress Responses with Focus on Cadmium: Review

The current state of heavy metal (HM) environmental pollution problems was considered in the review: the effects of HMs on the vital activity of plants and the functioning of their antioxidant system, including phenolic antioxidants. The latter performs an important function in the distribution and binding of metals, as well as HM detoxification in the plant organism. Much attention was focused on cadmium (Cd) ions as one of the most toxic elements for plants. The data on the accumulation of HMs, including Cd in the soil, the entry into plants, and the effect on their various physiological and biochemical processes (photosynthesis, respiration, transpiration, and water regime) were analyzed. Some aspects of HMs, including Cd, inactivation in plant tissues, and cell compartments, are considered, as well as the functioning of various metabolic pathways at the stage of the stress reaction of plant cells under the action of pollutants. The data on the effect of HMs on the antioxidant system of plants, the accumulation of low molecular weight phenolic bioantioxidants, and their role as ligand inactivators were summarized. The issues of polyphenol biosynthesis regulation under cadmium stress were considered. Understanding the physiological and biochemical role of low molecular antioxidants of phenolic nature under metal-induced stress is important in assessing the effect/aftereffect of Cd on various plant objects-the producers of these secondary metabolites are widely used for the health saving of the world's population. This review reflects the latest achievements in the field of studying the influence of HMs, including Cd, on various physiological and biochemical processes of the plant organism and enriches our knowledge about the multifunctional role of polyphenols, as one of the most common secondary metabolites, in the formation of plant resistance and adaptation.

Aphanothece sp. as promising biostimulant to alleviate heavy metals stress in Solanum lycopersicum L. by enhancing physiological, biochemical, and metabolic responses

Heavy metals (H.M) are a major environmental concern around the world. They have harmful impact on plant productivity and pose a serious risk to humans and animals health. In the present study, we investigated the effect of Aphanothece crude extract (ACE) on physiological, biochemical, and metabolic responses of tomato plant exposed to 2 mM Pb and Cd. The results showed a significant reduction of tomato plant weights and perturbation in nutrients absorption under 2 mM Pb and Cd conditions. Moreover, ACE treatment showed a significant enhancement of plant biomass compared to plants under Pb and Cd. On the other hand, ACE application favoured H.M accumulation in root and inhibited their translocation to shoot. In addition, ACE treatment significantly enhanced several stress responses in plant under Pb and Cd stress such as scavenging enzymes and molecules: POD, CAT, SOD, proline, and polyphenols etc. Furthermore, ACE treatment showed remodulation of metabolic pathways related to plant tolerance such as wax construction mechanism, particularly SFA, UFA, VLFA, alkanes, alkenes, and sterols biosynthesis to enhance tolerance and resistance to H.M stress. In the present study, we emphasized that ACE alleviates H.M stress by minimizing metal translocation to above-part of plant and enhancing plant growth, nutrients absorption, and biochemical responses.

A Multi-Method Approach for Impact Assessment of Some Heavy Metals on Lactuca sativa L

Heavy metals represent a large category of pollutants. Heavy metals are the focus of researchers around the world, mainly due to their harmful effects on plants. In this paper, the influence of copper, cadmium, manganese, nickel, zinc and lead, present in soil in different concentrations (below the permissible limit, the maximum permissible concentration and a concentration higher than the maximum permissible limit) on lettuce (Lactuca sativa L.) was evaluated. For this purpose, the authors analyzed the variation of photosynthetic pigments, total polyphenols, antioxidant activity and the elemental content in the studied plants. The experimental results showed that the variation of the content of biologically active compounds, elemental content and the antioxidant activity in the plants grown in contaminated soil, compared to the control plants, depends on the type and concentration of the metal added to the soil. The biggest decrease was recorded for plants grown in soil treated with Ni I (-42.38%) for chlorophyll a, Zn II (-32.92%) for chlorophyll b, Ni I (-40.46%) for carotenoids, Pb I (-40.95%) for polyphenols and Cu III (-29.42%) for DPPH. On the other hand, the largest increase regarding the amount of biologically active compounds was registered for Mn I (88.24%) in the case of the chlorophyll a, Mn I (65.56%) for chlorophyll b, Pb I (116.03%) for carotenoids, Ni III (1351.23%) for polyphenols and Ni III (1149.35%) for DPPH.

Synergistic impact of two autochthonous saprobic fungi (A. niger and T. pseudokoningii) on the growth, ionic contents, and metals uptake in Brassica juncea L. and Vigna radiata L. under tannery solid waste contaminated soil

Unrestricted disposal of tannery solid waste (TSW) into agricultural soils has resulted in the contamination of heavy metals (HMs) such as chromium (Cr) cadmium (Cd), Copper (Cu), and Zinc (Zn) along with the severe potential to degrade the environmental quality around the world. In the present study, a combined phyto- and myco-remediation strategy was evaluated to enhance the growth, ionic contents, and phytoextraction potential of Brassica juncea and Vigna radiata for HMs from TSW-contaminated soil. A pot experiment was conducted in the greenhouse using single or combined inoculation of Trichoderma pseudokoningii (Tp) and Aspergillus niger (An) in B. juncea and V. radiata under TSW-contaminated soil at different doses (0, 50, and 100%). The results showed that the growth parameters of both B. juncea and V. radiata were severely affected under 50 and 100% TSW treatment. The combined inoculation of both the fungal species ameliorated the positive impacts of 50 and 100% TSW application on growth and ionic contents accumulation in B. juncea and V. radiata. The combined application of An + Tp at 100% TSW enhanced the shoot length (87.8, 157.2%), root length (123.9, 120.6%), number of leaves (184.2, 175.0%), number of roots (104.7, 438.9%), and dry weight (179.4, 144.8%) of B. juncea and V. radiata, respectively as compared to control with any fungal treatment at 100% TSW. A single application of An at different doses of TSW enhanced the metal concentration in B. juncea, whereas Tp increased the concentration of the metals in V. radiata. The concentration of Cr in roots (196.2, 263.8%), shoots (342.4, 182.2%), Cu in roots (187.6, 137.0%), shoots (26.6, 76.0%), Cd in roots (245.2, 184.6%), shoots (142.1, 73.4%), Zn in roots (73.4, 57.5%), shoots (62.9, 57.6%), in B. juncea were increased by the application of An at 50 and 100% treatment levels of TSW, respectively compared to control (C). Moreover, the HMs (Cr, Cu, Cd, and Zn) uptake was also improved under 50 and 100% TSW with the combined inoculation of Tp + An in both B. juncea and V. radiata. In conclusion, the combined inoculation of Tp + An was more effective in metal removal from TSW-treated soil.NOVELTY STATEMENTLimited studies have been conducted on filamentous fungi systematically under metal-contaminated sites for their diversity, metal tolerance, and their potential in enhancing the phytoremediation potential of different crop plants.In the present study, single and/or combined inoculation of fungal strains was found effective in alleviating different metals stress in tannery solid waste contaminated soil by improving defense mechanisms and plant growth due to the association between fungal strains and plants.The combined application of both fungal strains had an additive effect in enhancing the bioaccumulation capacity of B. juncea and V. radiata compared to their single inoculation.

Subcellular distribution and physiological responses of native and exotic grasses from the Pampa biome subjected to excess manganese

Fungicides containing manganese (Mn) applied to control plant diseases increase the concentration of Mn in soils, which may potentiate Mn toxicity in acid soils. Some species of wild grasses, such as those from the Pampa biome located in South America, or even those introduced into this biome, may possess different mechanisms of tolerance to excess Mn. The present study aimed to evaluate the subcellular distribution and physiological and biochemical responses of exotic and native grasses from the Pampa biome, cultivated in Mn excess. The experiment was conducted in nutrient solution in a greenhouse, in an entirely randomized design, bifactorial 4 × 4, consisting of four Mn concentrations (2 [control], 300, 600 and 900 μM) and four species (two exotic: Avena strigosa and Lolium multiflorum; and two native: Paspalum notatum and Paspalum plicatulum). At 27 days of exposure to the treatments, biomass and growth rates, leaf gas exchange with the environment, photosynthetic pigment concentrations of malondialdehyde and H2O2, antioxidant enzyme activities (SOD and POD), and subcellular distribution of Mn were evaluated. Most of the grasses showed high concentration of Mn in tissues, mainly, in the shoot. In the presence of 900 μM Mn, more than 80% of the absorbed Mn was compartmentalized in the cell walls and vacuoles of the cells. Compartmentalization of Mn excess into metabolically less active organelles is the main tolerance factor in grasses. Physiological and biochemical responses were stimulated in the presence of 300 μM Mn, while 900 μM Mn negatively affected biochemical-physiological responses of grasses. The species L. multiflorum was most sensitive to excess Mn, while P. notatum was the most tolerant.

Physiological dynamics as indicators of plant response to manganese binary effect

Introduction

Heavy metals negatively affect plant physiology. However, plants can reduce their toxicity through physiological responses. Broussonetia papyrifera is a suitable candidate tree for carrying out the phytoremediation of manganese (Mn)-contaminated soil.

Methods

Considering that Mn stress typically exerts a binary effect on plants, to reveal the dynamic characteristics of the physiological indexes of B. papyrifera to Mn stress, we conducted pot experiments with six different Mn concentrations (0, 0.25, 0.5, 1, 2, and 5 mmol/L) for 60 days. In addition to the chlorophyll content, malondialdehyde (MDA), proline (PRO), soluble sugar, superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), the absorption and transfer characteristics of Mn, and root structure were also measured.

Results

Phytoremedial potential parameters such as the bioconcentration factor (BCF) and translocation factor (TF) displayed an increasing trend with the increase of Mn concentration. At lower Mn concentrations (<0.5 mmol/L), the TF value was <1 but crossed 1 when the Mn concentration exceeded 100 mmol/L. The Mn distribution in various tissues was in the following order: leaf > stem > root. The root structure analysis revealed that low-level concentrations of Mn (1 mmol/L) promoted root development. Mn concentration and stress duration had significant effects on all measured physiological indexes, and except soluble sugar, Mn concentration and stress time displayed a significant interaction on the physiological indexes.

Discussion

Our study demonstrates that the physiological indexes of B. papyrifera display dynamic characteristics under Mn stress. Thus, during the monitoring process of Mn stress, it appears to be necessary to appropriately select sampling parts according to Mn concentration.

The Status and Research Progress of Cadmium Pollution in Rice- (Oryza sativa L.) and Wheat- (Triticum aestivum L.) Cropping Systems in China: A Critical Review

The accumulation of cadmium in rice (Oryza sativa L.) and wheat (Triticum aestivum L.) is a serious threat to the safe use of farmland and to the health of the human diet that has attracted extensive attention from researchers. In this review, a bibliometric analysis was performed using a VOS viewer (1.6.18, Netherlands) to investigate the status of cadmium contamination in rice and wheat growing systems, human health risks, mechanisms of Cd uptake and transport, and the corresponding research hotspots. It has a certain reference value for the prevention and control of cadmium pollution in rice and wheat planting systems in China and abroad. The results showed that the Cd content in rice and wheat planting systems in the Yangtze River Basin was significantly higher than that in other areas of China, and the Cd content in rice and wheat grains and the hazard quotient (HQ) in Hunan Province was the highest. The average Cd concentration exceeded the recommended limit by about 62% for rice and 81% for wheat. The main reasons for the high Cd pollution in rice and wheat growing areas in Hunan are mining activities, phosphate fertilizer application, sewage irrigation, and electronic equipment manufacturing. In this review, we demonstrate that cadmium toxicity reduces the uptake and transport of essential elements in rice and wheat. Cadmium stress seriously affected the growth and morphology of plant roots. In the shoots, Cd toxicity was manifested by a series of physiological injuries, such as decreased photosynthesis, soluble protein, sugar, and antioxidant enzyme activity. Cadmium that accumulates in the shoots is transferred to grains and then passes up the food chain to people and animals. Therefore, methods for reducing cadmium content in grains of rice and wheat are urgently needed, especially in Cd-contaminated soil. Current research on Cd pollution in rice and wheat planting systems focuses on the bioavailability of Cd, soil rhizosphere changes in wheat and rice, and the role of antioxidant enzyme systems in alleviating heavy metal stress in rice and wheat.

Ameliorative role of foliar Zn-lysine application on wheat (Triticum aestivum L.) stressed by Tannery Wastewater

Tannery industries discharge a high concentration of chromium (Cr) along with other heavy metals, which are hazardous for all life forms. With increasing shortage of freshwater, tannery effluent is frequently used for crop an irrigation, causing damage to plants' health. In order to address this challenge, amino acid chelate fertilizer was used to investigate the impact on wheat crops against tannery waste water. Tannery wastewater (TW) was used at different levels such as 0%, 25%, 50%, and 100% with an amendment of foliar Zn-lysine (Zn-lys) at30 mg/L. This research highlighted the positive correlation of Zn-lysine on the morpho-physiological, biochemical, and gas exchange traits under different levels of tannery wastewater. The findings of this study showed that the application of Cr-rich tannery wastewater at different treatment levels resulted in a significant reduction in plant height (23%, 31%, and 36%), the number of tillers (21%, 30%, and 43%), spike (19%, 36%, and 55%) and dry weight (DW) of grains (10%, 25%, and 49%) roots DW (17%, 41%, 56%), and shoots DW (22%, 32%, and 47%) as compared to control. Foliar-applied Zn-lys positively enhanced photosynthetic attributes, antioxidant enzymes activities and gas exchange traits by reducing the oxidative stress alone and under Cr stress. The concentration of Cr in roots (21%, 37%, 38%) and shoots (11%, 36%, 37%) was reduced by the foliar application of Zn-lys at different treatment levels. These findings conclude that Zn-lys served as a protector for the growth and development of wheat and has an incredible potential to inhibit the phytotoxicity induced by excess Cr.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s12298-022-01265-6.

Proteomic analysis reveals molecular mechanism of Cd2+ tolerance in the leaves of halophyte Halogeton glomeratus

Halogeton glomeratus (H. glomeratus) is categorized as a halophyte, it can potentially endure not only salt but also heavy metals. The aim of this work was to study the molecular mechanisms underlying the Cd²⁺ tolerance of halophyte H. glomeratus seedlings. For that we used a combination of physiological characteristics and data-independent acquisition-based proteomic approaches. The results revealed that the significant changes of physiological characteristics of H. glomeratus occurred under approximately 0.4 mM Cd²⁺ condition and that Cd²⁺ accumulated in Cd²⁺-treated seedling roots, stems and leaves. At the early stage of Cd²⁺ stress, numerous differentially abundant proteins related to "phosphoenolpyruvate carboxylase", "transmembrane transporters", and "vacuolar protein sorting-associated protein" took important roles in the response of H. glomeratus to Cd²⁺ stress. At the later stage of Cd²⁺ stress, some differentially abundant proteins involved in "alcohol-forming fatty acyl-CoA reductase", "glutathione transferase", and "abscisic acid receptor" were considered to regulate the adaptation of H. glomeratus exposed to Cd²⁺ stress. Finally, we found various detoxification-related differentially abundant proteins related to Cd²⁺ stress. These biological processes and regulators synergistically regulated the Cd²⁺ tolerance of H. glomeratus. SIGNIFICANCE: The halophyte, H.glomeratus, has a strong tolerance to salinity, also survives in the heavy metal stress. At present, there are few reports on the comprehensive characterization and identification of Cd²⁺ response and adaption related regulators in H.glomeratus. This research focuses on the molecular mechanisms of H. glomeratus tolerance to Cd²⁺ stress at proteome levels to uncover the novel insight of the Cd²⁺-related biological processes and potential candidates involved in the response and adaption mechanism. The results will help elucidate the genetic basis of this species' tolerance to Cd²⁺ stress and develop application prospect of wild genetic resources to heavy metal phytoremediation.

Effects of urease-producing bacteria and eggshell on physiological characteristics and Cd accumulation of pakchoi (Brassica chinensis L.) plants

Soil cadmium (Cd) contamination resulting from anthropogenic activity poses severe threats to food safety and human health. In this study, a pot experiment was performed to evaluate the possibility of using urease-producing bacterium UR21 and eggshell (ES) waste for improving the physiological characteristics and reducing Cd accumulation of pakchoi (Brassica chinensis L.) plants. UR21 has siderophore and IAA production ability. The application of UR21 and ES individually or in combination could improve the root and shoot length, and fresh and dry weight of pakchoi plants under Cd stress. In Cd + ES + UR21-treated plants, the dry weight of shoot and root were increased by 61.54% and 72.73%, respectively. The chlorophyll a, chlorophyll b, and carotenoid content were increased by 52.19%, 42.95%, and 95.56% in Cd + ES + UR21-treated plants. Meanwhile, the H₂O₂ and MDA content were decreased while the SOD and POD activity were increased, and an increase of soluble protein level in pakchoi plants was observed under Cd + ES + UR21 treatment. Importantly, eggshell and UR21 alone or in combination induced a decline of Cd content in pakchoi plants, especially that Cd + ES + UR21 treatment decreased Cd content in shoot and root by 26.96% and 42.91%, respectively. Meanwhile, the soil urease and sucrase activities were enhanced. Generally, the combined application of ureolytic bacteria UR21 and eggshell exhibited better effects than applied them individually in terms of alleviating Cd toxicity in pakchoi plants. Our findings may give a unique perspective for an eco-friendly and sustainable strategy to remediate heavy metal-polluted soils.

Integrated physiological, transcriptomic and metabolomic analysis of the response of Trifolium pratense L. to Pb toxicity

Lead (Pb) interferes with plant gene expression, alters metabolite contents and affects plant growth. However, the molecular mechanism underlying the plant response to Pb is not completely understood. In the present study, Trifolium pratense L. was exposed to Pb concentrations of 0 (Pb0), 500 (Pb500), 1000 (Pb1000), 2000 (Pb2000) and 3000 (Pb3000) mg/kg in soils. Pb stress affected the ability of T. pratense to accumulate and transport Pb, increased the activity of peroxidase (POD) and the contents of malondialdehyde (MDA) and proline, decreased the amount of photosynthetic pigments and soluble proteins, and led to changes in growth and biomass. Transcriptomic and metabolomic analyses showed that Pb mainly affected eight pathways, and LHC, flavonoids, organic acids, amino acids and carbohydrates were upregulated or downregulated. Moreover, Pb500 induced the upregulation of serA, promoted the synthesis of citric acid, maintained photosynthetic pigment levels, and ultimately promoted an increase in stem length. Pb3000 induced the upregulation of ARF, GH3 and SAUR genes, but the saccharide contents and stem length decreased in response to Pb stress. We used a variety of methods to provide a molecular perspective on the mechanism underlying the response of T. pratense to Pb stress.

Sex-Specific Physiological Responses of Populus cathayana to Uranium Stress

Attention is increasingly being paid to the contamination of soil by the radioactive element uranium (U). Phytoremediation of contaminated soil by economically advantageous and environment-protective plants shows considerable potential for addressing this problem. Populus cathayana is a species with high heavy-metal tolerance, economic value, and notable potential for phytoremediation. Plant-sex-related differences can lead to differences in vegetative growth and tolerance to various stressors. As such, in this study, we designed a pot experiment to analyze the responses of male and female trees of P. cathayana to 50 mg kg−1 U stress in contaminated soil for 3 months. We studied the U uptake and distribution, photosynthesis, chlorophyll fluorescence, active oxygen species, and antioxidant enzymes of P. cathayana. The results showed that the photosynthetic activity and chlorophyll fluorescence of male and female trees were similar, and U stress mainly affected the nonstomatal factors and photosystem II during photosynthesis. Regarding the physiological and biochemical processes, male and female trees showed different defense strategies: male trees had higher peroxidase (POD), H2O2, and soluble sugars, but lower malondialdehyde (MDA), superoxide dismutase (SOD), and soluble proteins. Under U stress, the active oxygen produced by male trees could be cleared by antioxidant enzymes, preventing damage to the cell membrane. Male trees accumulated a higher U concentration in their roots than female trees, whereas the transportation of U from roots to leaves in male trees was lower than that in female trees. Therefore, our results suggested that male trees have a higher tolerance capacity and greater ability to remediate U-polluted soil than female trees. Future phytoremediation studies should consider the differences between plant sexes in the tolerance to U-contaminated land.

Enhancing the Phytoremediation of Heavy Metals by Combining Hyperaccumulator and Heavy Metal-Resistant Plant Growth-Promoting Bacteria

Heavy metals (HMs) have become a major environmental pollutant threatening ecosystems and human health. Although hyperaccumulators provide a viable alternative for the bioremediation of HMs, the potential of phytoremediation is often limited by the small biomass and slow growth rate of hyperaccumulators and HM toxicity to plants. Here, plant growth-promoting bacteria (PGPB)-assisted phytoremediation was used to enhance the phytoremediation of HM-contaminated soils. A PGPB with HM-tolerant (HMT-PGPB), Bacillus sp. PGP15 was isolated from the rhizosphere of a cadmium (Cd) hyperaccumulator, Solanum nigrum. Pot experiments demonstrated that inoculation with strain PGP15 could significantly increase the growth of S. nigrum. More importantly, strain PGP15 markedly improved Cd accumulation in S. nigrum while alleviating Cd-induced stress in S. nigrum. Specifically, PGP15 inoculation significantly decreased the contents of H₂O₂, MDA, and O 2 · - in S. nigrum, while the activities (per gram plant fresh weight) of SOD, APX, and CAT were significantly increased in the PGP15-inoculated plants compared with the control sample. These results suggested that the interactions between strain PGP15 and S. nigrum could overcome the limits of phytoremediation alone and highlighted the promising application potential of the PGPB-hyperaccumulator collaborative pattern in the bioremediation of HM-contaminated soils. Furthermore, the PGP15 genome was sequenced and compared with other strains to explore the mechanisms underlying plant growth promotion by HMT-PGPB. The results showed that core genes that define the fundamental metabolic capabilities of strain PGP15 might not be necessary for plant growth promotion. Meanwhile, PGP15-specific genes, including many transposable elements, played a crucial role in the adaptive evolution of HM resistance. Overall, our results improve the understanding of interactions between HMT-PGPB and plants and facilitate the application of HMT-PGPB in the phytoremediation of HM-contaminated soils.

Commercial Red Food Dyes Preparations Modulate the Oxidative State in Three Model Organisms (Cucumis sativus, Artemia salina, and Danio rerio)

The growing environmental spreading of food synthetic dyes and bio-colors have the potential for altering organisms’ redox states. Here, three model species for aquatic pollution trials, Cucumis sativus seeds, Artemia salina cysts, and Danio rerio embryos, were short-term exposed to a fixed concentration of the artificial red E124, and two red bio-colors, cochineal E120, and vegan red (VEGR). In the animal models, we evaluated the total reactive oxygen species (ROS) and the susceptibility to in vitro oxidative stress, and in C. sativus, H2O2 production and antioxidant capacity. We also measured organismal performance indices (routine oxygen consumption in the animal models, dark oxygen consumption, and photosynthetic efficiency in C. sativus). In C. sativus, only E124 increased ROS and affected dark oxygen consumption and photosynthetic efficiency, while all dyes enhanced the antioxidant defenses. In the A. salina nauplii, all dyes increased ROS, while E120 and E124 reduced the susceptibility to oxidative stress. In D. rerio, treatments did not affect ROS content, and reduced oxidative stress susceptibility. Our data show that red food dyes affect the redox state of the developing organisms, in which ROS plays a significant role. We suggest a potentially toxic role for red food dyes with environmentally relevant consequences.

Plants-Microorganisms-Based Bioremediation for Heavy Metal Cleanup: Recent Developments, Phytoremediation Techniques, Regulation Mechanisms, and Molecular Responses

Rapid industrialization, mine tailings runoff, and agricultural activities are often detrimental to soil health and can distribute hazardous metal(loid)s into the soil environment, with harmful effects on human and ecosystem health. Plants and their associated microbes can be deployed to clean up and prevent environmental pollution. This green technology has emerged as one of the most attractive and acceptable practices for using natural processes to break down organic contaminants or accumulate and stabilize metal pollutants by acting as filters or traps. This review explores the interactions between plants, their associated microbiomes, and the environment, and discusses how they shape the assembly of plant-associated microbial communities and modulate metal(loid)s remediation. Here, we also overview microbe-heavy-metal(loid)s interactions and discuss microbial bioremediation and plants with advanced phytoremediation properties approaches that have been successfully used, as well as their associated biological processes. We conclude by providing insights into the underlying remediation strategies' mechanisms, key challenges, and future directions for the remediation of metal(loid)s-polluted agricultural soils with environmentally friendly techniques.

Assessment of cadmium and lead tolerance potential of quinoa (Chenopodium quinoa Willd) and its implications for phytoremediation and human health

Soil contamination with Cd and Pb is a worldwide problem which not only degrades the environment but also poses a serious threat for human and animal health. Phytoremediation of these contaminated soils using halophytic plants like quinoa presents an opportunity to clean the soils and use them for crop production. The current experiment was performed to evaluate the Cd and Pb tolerance potential of quinoa and subsequently its implications for human health. Three weeks old quinoa seedlings were exposed to Cd (30, 60 and 90 mg kg^-1) and Pb (50, 100 and 150 mg kg^-1) levels along with a control. The results revealed that plant height decreased at highest levels of soil Cd and Pb. Shoot, root and seed dry weight decreased with increasing levels of soil Cd and Pb. Tissue Cd and Pb concentrations increased with increasing levels of Cd and Pb in soil, the highest Cd was found in roots while the lowest in seeds. The highest Pb concentration was found in shoots at low Pb level, while in roots at high level of Pb. Increasing levels of Cd and Pb stimulated the activities of measured antioxidant enzymes and decreased membrane stability index. The health risk assessments of Cd and Pb revealed that hazard quotient was < 1 for both the metals. However, the results of total hazard quotient showed that value was < 1 for Pb and 1.19 for Cd showing potential carcinogenicity. This study demonstrates that quinoa has good phytoremediation potential for Cd and Pb however, the risk of Cd toxicity is challenging for human health.

Phytoremediation potential of Bermuda grass (Cynodon dactylon (L.) pers.) in soils co-contaminated with polycyclic aromatic hydrocarbons and cadmium

Soils co-contaminated with polycyclic aromatic hydrocarbons (PAHs) and cadmium (Cd) have serious environmental impacts and are highly toxic to humans and ecosystems. Phytoremediation is an effective biotechnology for the remediation and restoration of PAH- and Cd-polluted soils. Pot experiments were conducted to investigate the individual and combined effects of PAHs (1238.62 mg kg-1) and Cd (23.1 mg kg-1) on the phytoremediation potential of Bermuda grass grown in contaminated soils. Bermuda grass exhibited a significant decrease in plant growth rate, leaf pigment content, root activity, plant height and biomass and a remarkable increase in malondialdehyde content and electrolyte leakage when grown in PAH- and Cd-contaminated soils compared with grass grown in uncontaminated soils. The activity of soil enzymes, including urease, alkaline phosphatase, sucrose, and fluorescein diacetate hydrolysis, were reduced in soil with PAH and Cd stress. Furthermore, the toxicity of combined PAHs and Cd on Bermuda grass growth and soil enzyme activity was much higher than that of PAH or Cd stress alone, suggesting a synergistic effect of PAHs and Cd on cytotoxicity. To scavenge redundant reactive oxygen species and avoid oxidative damage, Bermuda grass increased plant catalase, superoxide dismutase, and peroxidase activity and soluble sugar and proline content. The bioconcentration factor of Cd in Bermuda grass grown under Cd alone and combined PAH and Cd exposure was greater than 1 for both, suggesting that Bermuda grass has a high Cd accumulation ability. Under PAH alone and combined PAH and Cd exposure conditions, a higher PAH removal rate (41.5-56.8%) was observed in soils planted with Bermuda grass than in unplanted soils (24.8-29.8%), indicating that Bermuda grass has a great ability to degrade PAHs. Bermuda grass showed great phytoremediation potential for the degradation of PAHs and phytoextraction of Cd in co-contaminated soils.

Nitrogen addition alleviated sexual differences in responses to cadmium toxicity by regulating the antioxidant system and root characteristics, and inhibiting Cd translocation in mulberry seedlings

Cadmium (Cd) toxicity and nitrogen (N) deposition are two major environmental stresses which can affect plant growth. It's less clear that how the combined Cd accumulation and N deposition affect the male and female plants of dioecious species. The aim of the present study was to detect sex-specific responses to Cd stress and simulated N deposition in one-year-old male, female and hermaphrodite seedlings of Morus alba. Changes in morphology, physiology, root architecture and biomass of the three sex types of mulberry seedlings were determined. The results showed that Cd toxicity caused limited growth, impaired photosynthetic apparatus and decreased gas exchange rates with significant sex-specific differences. Mulberry was found to deploy detoxification mechanisms to avoid or tolerate toxic Cd effects through the activation of the antioxidant system, increasing proline and non-protein thiol contents, translocating Cd into different plant parts and decreasing biomass. Females displayed a low tolerance to high Cd and were more sensitive to Cd stress. Simulated N deposition alleviated the negative effects of Cd on leaves and decreased sex-specific differences in the three kinds of mulberry seedlings, but N fertilizer did not affect the total biomass. The N-stimulated increasing in proline and non-protein thiol contents might play a crucial role in resisting the damage caused by Cd stress, and the three kinds of mulberry seedlings had slightly different ways of improving Cd tolerance by N deposition. Sexual differences in Cd accumulation are correlated with root architecture. This study provides evidence for the utilization of mulberry to treat Cd-contaminated soils under N deposition.

NTA-assisted mineral element and lead transportation in Eremochloa ophiuroides (Munro) Hack

Lead (Pb) is one of the most toxic and harmful pollutants to the environment and human health. Centipedegrass (Eremochloa ophiuroides (Munro) Hack.), an excellent ground cover plant for urban plant communities, exhibits the outstanding lead tolerance and accumulation. Nitrilotriacetic acid (NTA) is an environmentally friendly chelating agent that strengthens phytoremediation. This study explored the effects of different NTA concentrations on the absorption and transportation of mineral elements and Pb in centipedegrass. Following exposure to Pb (500 μM) for 7 days in hydroponic nutrient solution, NTA increased root Mg, K, and Ca concentrations and shoot Fe, Cu, and Mg concentrations and significantly enhanced the translocation factors of mineral elements to the shoot. Although NTA notably decreased root Pb absorption and accumulation, it significantly enhanced Pb translocation factors, and the Pb TF value was the highest in the 2.0 mM NTA treatment. Furthermore, the shoot translocation of Pb and mineral elements was synergistic. NTA can support mineral element homeostasis and improve Pb translocation efficiency in centipedegrass. Regarding root radial transport, NTA (2.0 mM) significantly promoted Pb transport by the symplastic pathway under the treatments with low-temperature and metabolic inhibitors. Meanwhile, NTA increased apoplastic Pb transport at medium and high Pb concentrations (200-800 μM). NTA also enhanced the Pb radial transport efficiency in roots and thus assisted Pb translocation. The results of this study elucidate the effects of NTA on the absorption and transportation of mineral elements and Pb in plants and provide a theoretical basis for the practical application of the biodegradable chelating agent NTA in soil Pb remediation.

Effect of Pb-Contaminated Water on Ludwigia stolonifera (Guill. & Perr.) P.H. Raven Physiology and Phytoremediation Performance

A laboratory experiment was led to examine the lead bioaccumulation capacity of Ludwigia stolonifera (Guill. & Perr.) exposed to various Pb concentrations (0, 10, 25, 50, and 100 mg/L) for 1, 3, 5, and 7 days. The lead accumulation increased as the metal concentrations in the solution increased and over time, to an extreme accretion of 6840 mg/kg DW(dry weight) at 100 mg/L of lead on the 10 days exposure. The proportion removal efficiency, translocation factor, and bioconcentration factor of the plant were assessed. The maximum bioconcentration factor values (1981.13) indicate that the plant was a Pb hyperaccumulator, and translocation factor values (1.85), which are >1, indicate fit of L. stolonifera for eliminating Pb in Pb-contaminated water. Photosynthetic pigments were decreased with increase of Pb concentration and time exposure. Total chlorophyll content and Chl a/b ratio lowered to between 46 and 62% at 100 mg/L Pb after 10 days exposure. Protein content and soluble carbohydrate indicated a similar trend, which showed the highest decrease (7.26 and 36.2 mg/g FW(fresh weight), respectively) at 100 mg/L of Pb after 10 days. The activity of the antioxidant enzymes superoxide dismutase, ascorbate, and peroxidase was increased significantly in comparison to the control. The results indicate that L. stolonifera is a newly recognized Pb hyperaccumulator (6840 mg/kg DW), but physiological status indicates that the plant is not tolerant to high Pb concentrations.

Leaf color formation mechanisms in Alternanthera bettzickiana elucidated by metabolite and transcriptome analyses

The difference in leaf color among the three cultivars of A. bettzickiana is due to different chloroplast morphology and chlorophyll-to-anthocyanin ratios. Alternanthera bettzickiana is one of the most important ornamental plants in modern flower beds because of its colorful leaves. The present study examined the mechanism of leaf color formation in A. bettzickiana. Three cultivars of A. bettzickiana (red, green, and mixed red and green) were selected for comprehensive analyses of leaf color formation by examining cellular and subcellular structures and pigment biosynthesis and metabolism. The difference in leaf colors between the three cultivars of A. bettzickiana was due to different chlorophyll-to-anthocyanin ratios. A. bettzickiana 'Green' showed very low expression of CHS, F3H, and DFR, the key genes of the anthocyanin biosynthesis pathway, and a low anthocyanin content but had mature chloroplasts and a green color. A. bettzickiana 'Red' exhibited a low chlorophyll content and deformed chloroplasts but a high cyanidin content and, thus, a red color. A. bettzickiana 'Variegated' presented high anthocyanin and chlorophyll contents and exhibited red and green variegation, indicating a balance between coloration and photosynthetic efficiency. These data provide a good explanation for the coloration of different cultivars of A. bettzickiana and an important reference for better explaining the color formation mechanisms of plant leaves.

Phytoextraction of metal(loid)s from contaminated soils by six plant species: A field study

Phytoextraction is an in situ remediation technique that uses (hyper)accumulator plant species to extract metal(loid)s from contaminated soils. Field studies can help in selecting appropriate plants for phytoextraction and in better understanding their phytoextraction performance. Hence, a field study was conducted using six (hyper)accumulator species (Solanum nigrum L., Bidens pilosa L., Xanthium strumarium L., Helianthus annuus L., Lonicera japonica T. and Pennisetum sinese R.) over two years in Jiaoxi town, Liuyang city, Hunan Province, China, to determine the effect of the (hyper)accumulator rhizospheres on field soils contaminated with multiple metal(loid)s and to analyze the variations in rhizosphere soil microbial community diversity and composition. After two years of field experiments, compared to the other four (hyper)accumulators, Bidens pilosa L. and Xanthium strumarium L. exhibited not only better metal(loid) phytoextraction abilities but also higher shoot biomasses. The contents of diethylenetriaminepentaacetic acid (DTPA)-extractable Pb, Cd and Zn decreased in the rhizosphere soils of all six (hyper)accumulators after repeated phytoextraction. Moreover, our findings illustrated that hyperaccumulator planting helps improve and rebuild the soil bacterial community composition and structure in contaminated soils by shifting the soil physiochemical properties. After repeated planting, the soil bacterial communities were reconstructed and dominated by Proteobacteria, Actinobacteriota, Chloroflexi and Acidobacteriota at the phylum level. The soil fungal communities were dominated by Ascomycota, Basidiomycota and Mortierellomycota at the phylum level. The reconstruction of soil microbial communities may help (hyper)accumulators adapt to metal(loid)-contaminated environments and improve their phytoextraction abilities.

Exposure routes, bioaccumulation and toxic effects of per- and polyfluoroalkyl substances (PFASs) on plants: A critical review

Per- and polyfluoroalkyl substances (PFASs) are artificial persistent organic pollutants ubiquitous in ecosystem, and their bioaccumulation and adverse outcomes in plants have attracted extensive concerns. Here, we review the toxic effects of PFASs encountered by various plants from physiological, biochemical and molecular perspectives. The exposure routes and bioaccumulation of PFASs in plants from contaminated sites are also summarized. The bioaccumulation of PFASs in plants from contaminated sites varied between ng/g and μg/g levels. The 50% inhibition concentration of PFASs for plant growth is often several orders of magnitude higher than the environmentally relevant concentrations (ERCs). ERCs of PFASs rarely lead to obvious phenotypic/physiological damages in plants, but markedly perturb some biological activities at biochemical and molecular scales. PFAS exposure induces the over-generated reactive oxygen species and further damages plant cell structure and organelle functions. A number of biochemical activities in plant cells are perturbed, such as photosynthesis, gene expression, protein synthesis, carbon and nitrogen metabolisms. To restore the desire states of cells exposed to PFASs, plants initiate several detoxifying mechanisms, including enzymatic antioxidants, non-enzymatic antioxidants, metallothionein genes and metabolic reprogramming. Future challenges and opportunities in PFAS phytotoxicity studies are also proposed in the review.

Bioavailability, Accumulation and Distribution of Toxic Metals (As, Cd, Ni and Pb) and Their Impact on Sinapis alba Plant Nutrient Metabolism

This study presents the behavior of white mustard seedlings Sinapis alba grown for three months in laboratory polluted soil containing As, Cd, Ni and Pb. Four different experiments were performed in which As was combined with the other three toxic metals in different combinations (As, AsCd, AsCdNi, AsCdNiPb), keeping the same concentrations of As and Cd in all tests and following the national soil quality regulations. The effects of these metals were monitored by the analytical control of metal concentrations in soil and plants, bioavailability tests of mobile metal fractions using three different extracting solutions (DTPA + TEA + CaCl₂-DTPA, DTPA + CaCl₂-CAT, and CH₃COONH₄ + EDTA-EDTA) and calculation of bioaccumulation and translocation factors. Additionally, micro, and macro-nutrients both in soil and plant (root, stem, leaves, flowers and seeds) were analyzed in order to evaluate the impact of toxic metals on plant nutrient metabolism. Metals were significantly and differently accumulated in the plant tissues, especially under AsCdNi and AsCdNiPb treatments. Significant differences (p < 0.05) in the concentration of both As and Cd were highlighted. Translocation could be influenced by the presence of other toxic metals, such as Cd, but also of essential metals, through the competition and antagonism processes existing in plant tissues. Significantly, more Cd and Ni levels were detected in leaves and flowers. Cd was also detected in seeds above the WHO limit, but the results are not statistically significant (p > 0.05). The extraction of metallic nutrients (Zn, Cu, Mn, Ni, Mg, K, Fe, Ca, Cr) in the plant was not influenced by the presence of toxic metal combinations, on the contrary, their translocation was more efficient in the aerial parts of the plants. No phytotoxic effects were recorded during the exposure period. The most efficient methods of metal extraction from soil were for As-CAT; Cd-all methods; Pb and Ni-DTPA. The Pearson correlations (r) between applied extraction methods and metal detection in plants showed positive correlations for all toxic metals as follows: As-CAT > DTPA > EDTA, Cd-DTPA > CAT > EDTA, Ni-EDTA = DTPA > CAT, Pb-EDTA = DTPA = CAT). The results revealed that Sinapis alba has a good ability to accumulate the most bioavailable metals Cd and Ni, to stabilize As at the root level and to block Pb in soil.

Bacillus pumilus induced tolerance of Maize (Zea mays L.) against Cadmium (Cd) stress

Heavy metals contaminate the soil that alters the properties of soil and negatively affect plants growth. Using microorganism and plant can remove these pollutants from soil. The present investigation was designed to evaluate the induced effect of Bacillus pumilus on maize plant in Cadmium (Cd) contaminated soil. Three different concentrations of Cd (i.e. 0.25, 0.50 and 0.75 mg kg^-1) were applied in soil under which maize plants were grown. The germination percentage, shoot length, leaf length, number of leaves, root length, fresh weight and nutrient uptake by maize plant were determined. The experiment was conducted by using complete randomized design (CRD) with three replicates. The result indicated that germination percentage, Shoot length, leaf length, root length, number of leaves, and plant fresh weight were reduced by 37, 39, 39, 32 and 59% respectively at 0.75 mg kg^-1 of CdSO₄ concentration but when maize seeds inoculated with Bacillus pumilus significantly increased the germination percentage, shoot length, leaf length, number of leaves, plant fresh weight at different concentrations of CdSO₄. Moreover, the plant protein were significantly increased by 60% in T6 (0.25 mg kg^-1 of CdSO₄ + inoculated seed) and Peroxidase dismutase (POD) was also significantly higher by 346% in T6 (0.25 mg kg^-1 of CdSO₄ + inoculated seed), however, the Superoxide dismutase (SOD) was significantly higher in T5 (0.75 mg kg^-1 of CdSO₄ + uninoculated seed) and was 769% higher as compared to control. The Cd contents in Bacillus pumilus inoculated maize roots and shoots were decreased. The present investigations indicated that the inoculation of maize plant with Bacillus pumilus can help maize plants to withstand Cd stress but higher concentration of Cd can harm the plant. The Bacillus pumilus has good potential to remediate Cd from soil, and also have potential to reduce the phyto availability and toxicity of Cd.

Tolerance capacities of Broussonetia papyrifera to heavy metal(loid)s and its phytoremediation potential of the contaminated soil

Broussonetia papyrifera, is a promising fast-growing woody plant for the phytoremediation of heavy metal(loid) (HM)-contaminated soil. In this study, a greenhouse experiment was conducted to explore the tolerance capacities of B. papyrifera and its phytoremediation potential in the HM-contaminated soil. The results indicated that B. papyrifera could effectively decrease malondialdehyde (MDA) content by enhancing the antioxidant enzyme activities along with the cultivation in the HM-contaminated soil. Significant (p < 0.05) negative relationships were found between MDA content and superoxide dismutase (r = -0.620) and catalase activities (r = -0.702) in B. papyrifera leaves. Fourier Transform Infrared Spectroscopy analysis indicated that the main functional groups in B. papyrifera roots were slightly influenced by HMs, and organic acids, carbohydrates, protein, and amino acids might bind with HMs in plant roots to alleviate the adverse effect of HMs on plants growth. Meanwhile, B. papyrifera had great potential used for the phytoextraction of Cd and Zn in HM-contaminated soil. The maximum total Cd and Zn accumulation amount in B. papyrifera shoots could attach to 2.26 and 66.8 mg·pot^-1, respectively. These observations suggested that B. papyrifera has large biomass and high tolerance to HMs, which can be regarded as a promising plant for the eco-remediation of HM-contaminated sites.Novelty statement In this study, a fast-growing woody plant, Broussonetia papyrifera, was used for heavy metal(loid) (HM)-contaminated soil remediation. We found that B. papyrifera can effectively alleviate the adverse effect of HMs on plant growth by enhancing the antioxidant enzyme activities in leaves and binding HMs with organic acids, carbohydrates, protein, and amino acids in roots. Furthermore, the maximum total Cd and Zn accumulation amount in B. papyrifera shoots could attach to 2.26 and 66.8 mg·pot^-1, which suggested that B. papyrifera might be regarded as a promising woody plant used for the phytoextraction of Cd and Zn in the contaminated soil.

Elemental and Thermo-gravimetric Characterization of Trace Metals in Leaves and Soils as Bioindicators of Pollution in Kyiv City

In this study, leaf and soil samples were used as bio-monitors for different alkali and heavy metals at six different locations in Kyiv city. Using x-y plots of the inductively coupled plasma optical emission spectroscopy (ICP-OES) data measured the discrepancy level in elemental composition between the different investigated areas; the correlation between the concentrations in tree leaves and the samples from the surrounding soils were investigated. While the concentration of essential mineral elements and metals was found to be similar in several leaf and soil samples, in other samples, their concentration spread up to more than one order of magnitude. The concentration of metals was found to be higher in soil samples than in leaves. Thermo-gravimetric analysis (TGA) data helped to further characterize both types of samples. The metal removal during the incineration of the leaves was investigated by coupling a thermo-gravimetric analyzer to an inductively coupled plasma optical emission spectrometer (TGA-ICP-OES). The release of Cd, K, Na, Pb, and Zn during incineration at temperatures up to 960 °C was online monitored, and some insights were drawn about the behavior of such metals and the chemistry involved in the volatilization process.

Streptomyces pactum and sulfur mediated the rhizosphere microhabitats of potherb mustard after a phytoextraction trial

To explore the performance of Streptomyces pactum (Act12) alone (A) and jointly with sulfur (SA) in the phytoextraction practice of potentially toxic elements (PTEs) (Cd and Zn), as well as their effects on soil chemical properties and microbial community composition, this paper selected potherb mustard (Brassica juncea, Coss.) as the test plant to assess the feedback of soil-plant ecosystems. Metal uptake values in lone Act12 treatments were higher than that of Act12 + sulfur treatments, and showed dose dependent with Act12 due to the higher biomass production. According to the biochemical analyses of rhizosphere soils, Act12 inoculation significantly increased urease (20.4%) and dehydrogenase (58.5%) while reducing alkaline phosphatase (68.0%) activity. The production of soil organic acids was, in descending order, formic acid > oxalic acid > malic acid > propionic acid and indicated a stimulated variation under treatments (SA > A > control). High-throughput sequencing revealed that bacterial community compositions were consistent in both phylum and genus taxonomies, while the final overall proportions were modified. The populations of the predominant phyla Proteobacteria and Bacteroidetes increased after sulfur application. The contribution of Act12 to the relative abundance of microbiota was minor compared to sulfur. Based on a redundancy analysis, soil chemical properties are the drivers of microbial activities and the main contributor to plant growth. Our results suggested Act12 inoculation may be part of an effective strategy enhancing phytoremediation of PTE-contaminated soils through chemical and biotic processes, and provided important implications for sustainable land utilization and crop production.

Foliar application of seed water extract of Nigella sativa improved maize growth in cadmium-contaminated soil

Cadmium (Cd) is a widespread heavy metal, which commonly exert negative impacts on agricultural soils and living organisms. Foliar application of seed water extract of black cumin (Nigella sativa L.) can mitigate the adverse impacts of Cd-toxicity in plants through its rich antioxidants. This study examined the role of seed water extracts of N. sativa (NSE) in mitigating the adverse impacts of Cd-toxicity on maize growth. Two maize genotypes (synthetic ‘Neelum’ and hybrid ‘P1543’) were grown under 0, 4, 8 and 12 mg Cd kg^-1 soil. The NSE was applied at three different concentrations (i.e., 0, 10 and 20%) as foliar spray at 25 and 45 days after sowing. All Cd concentrations had no effect on germination percentage of both genotypes. Increasing Cd concentration linearly decreased root and allometric attributes, gas exchange traits and relative water contents of hybrid genotype. However, gas exchange traits of synthetic genotype remained unaffected by Cd-toxicity. Overall, hybrid genotype showed better tolerance to Cd-toxicity than synthetic genotype with better germination and allometric attributes and less Cd accumulation. Foliar application of NSE lowered negative effects of Cd-toxicity on all studied traits, except relative water contents. In conclusion, foliar application of NSE seemed a viable option to improve maize growth in Cd-contaminated soil.

Advances and Applications of Water Phytoremediation: A Potential Biotechnological Approach for the Treatment of Heavy Metals from Contaminated Water

Potable and good-quality drinking water availability is a serious global concern, since several pollution sources significantly contribute to low water quality. Amongst these pollution sources, several are releasing an array of hazardous agents into various environmental and water matrices. Unfortunately, there are not very many ecologically friendly systems available to treat the contaminated environment exclusively. Consequently, heavy metal water contamination leads to many diseases in humans, such as cardiopulmonary diseases and cytotoxicity, among others. To solve this problem, there are a plethora of emerging technologies that play an important role in defining treatment strategies. Phytoremediation, the usage of plants to remove contaminants, is a technology that has been widely used to remediate pollution in soils, with particular reference to toxic elements. Thus, hydroponic systems coupled with bioremediation for the removal of water contaminants have shown great relevance. In this review, we addressed several studies that support the development of phytoremediation systems in water. We cover the importance of applied science and environmental engineering to generate sustainable strategies to improve water quality. In this context, the phytoremediation capabilities of different plant species and possible obstacles that phytoremediation systems may encounter are discussed with suitable examples by comparing different mechanistic processes. According to the presented data, there are a wide range of plant species with water phytoremediation potential that need to be studied from a multidisciplinary perspective to make water phytoremediation a viable method.

Phytoextraction of Lead Using a Hedge Plant [Alternanthera bettzickiana (Regel) G. Nicholson]: Physiological and Biochemical Alterations through Bioresource Management

Phytoremediation is a cost-effective and environmentally friendly approach that can be used for the remediation of metals in polluted soil. This study used a hedge plant–calico (Alternanthera bettzickiana (Regel) G. Nicholson) to determine the role of citric acid in lead (Pb) phytoremediation by exposing it to different concentrations of Pb (0, 200, 500, and 1000 mg kg−1) as well as in a combination with citric acid concentration (0, 250, 500 µM). The analysis of variance was applied on results for significant effects of the independent variables on the dependent variables using SPSS (ver10). According to the results, maximum Pb concentration was measured in the upper parts of the plant. An increase in dry weight biomass, plant growth parameters, and photosynthetic contents was observed with the increase of Pb application (200 mg kg−1) in soil while a reduced growth was experienced at higher Pb concentration (1000 mg kg−1). The antioxidant enzymatic activities like superoxide dismutase (SOD) and peroxidase (POD) were enhanced under lower Pb concentration (200, 500 mg kg−1), whereas the reduction occurred at greater metal concentration Pb (1000 mg kg−1). There was a usual reduction in electrolyte leakage (EL) at lower Pb concentration (200, 500 mg kg−1), whereas EL increased at maximum Pb concentration (1000 mg kg−1). We concluded that this hedge plant, A. Bettzickiana, has the greater ability to remediate polluted soils aided with citric acid application.

Ornamental plants for the phytoremediation of heavy metals: Present knowledge and future perspectives

Environmental matrices are polluted with the plethora of contaminants, and among these, the concerns related to heavy metals (HMs) are also included. Due to the low cost in a long-term application and environmental friendliness, the use of biological remediation has gained significant attention in recent decades. The use of ornamental plants (OPs) in the field of phytoremediation is scarcely reported, and the impacts of HMs on OPs have also not been investigated in great depth. The OPs mediated HMs remediation can simultaneously remove contaminants and bring improvement in aesthetics of the site. The biomass of OPs produced after such activities can be used and sold as pot plants, cut flowers, essential oils, perfumes, air fresheners production, metal phytomining, and feedstock in silk production. The OPs also present a lower risk of HMs bioaccumulation compared to crop plants. This review focuses on the current knowledge of HMs toxicity to OPs, their applicability advantages, methods to improve the tolerance of OPs with incremented HMs uptake, challenges in the field, and future application perspectives. The case studies realted to practical application of OPs, from China, Iran, India, Oman, Pakistan, and Turkey, were also discussed. This work fetches the inter-disciplinary features and understanding for the sustainable treatment of HMs in a new novel way, to which no previous review has focused.

Potential of Eucalyptus globulus for the phytoremediation of metals in a Moroccan iron mine soil-a case study

The contamination left by abandoned mines demands sustainable mitigation measures. Hence, the aim of this study was to examine the phytoremediator ability of Eucalyptus globulus Labill. to be used for cleaning up metal-contaminated soils from an African abandoned iron (Fe) mine (Ait Ammar, Oued Zem, Morocco). Plantlets of this species were exposed to a control (CTL), a reference (REF), and a mine-contaminated soil (CS). Morphological (growth, leaf area) and physiological stress biomarkers (photosynthetic efficiency, pigments content, leaf relative water, and malondialdehyde (MDA) levels) and metal bioaccumulation were assessed. The growth and leaf area of E. globulus increased overtime in all soils, although at a lower rate in the CS. Its photosynthetic efficiency was not markedly impaired, as well as MDA levels decreased throughout the experiment in CS. In this soil, higher metal contents were detected in E. globulus roots than in leaves, especially Fe (roots: 15.98-213.99 μg g^-1; leaves: 5.97-15.98 μg g^-1) and Zn (roots: 1.64-1.99 μg g^-1; leaves: 0.67-1.19 μg g^-1), indicating their reduced translocation. Additionally, though at low extent, the plants bioaccumulated some metals (Pb > Zn > Cu) from CS. Overall, E. globulus may be potentially used for the phytoremediation of metals in metal-contaminated soils.

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.

Influences of Heavy Metals and Salt on Seed Germination and Seedling Characteristics of Halophyte Halogeton glomeratus

Heavy metals pollution and salinization of soils are widely distributed in agricultural soils. This study investigated the effects of five heavy metals and five heavy metals-contaminated salt on seed germination and seedling growth of halophyte Halogeton glomeratus (H. glomeratus). The results showed that seed germination, fresh weight (FW), dry weight (DW), radicles relative viability and ion contents (Cu²⁺, Ni²⁺, Zn²⁺, Cd²⁺ and Pb²⁺) of H. glomeratus were affected by different heavy metals and heavy metal-polluted 100 mM NaCl treatments. Ion contents in plumules increased with the increase of heavy metal concentrations with or without NaCl addition. Moreover, the accumulation levels of metals in the concentrations of Cu²⁺, Zn²⁺ and Pb²⁺ supplying 100 mM NaCl were higher than that without NaCl treatment. This can provide new insights into the value of H. glomeratus for phytoremediation of soil affected by heavy metals and also in combination with salinity.

Stress response and tolerance to perfluorooctane sulfonate (PFOS) in lettuce (Lactuca sativa)

Comprehensive understanding of stress response and tolerance to perfluorooctane sulfonate (PFOS) in plants at physiological, biochemical and molecular levels is scarce. Here, lettuce was cultivated in hydroponic media, to investigate the cross-talk among reactive oxygen species (ROS) production, oxidative damage, antioxidative defense and metabolic regulation in different parts of plants. Under exposure to 5 and 50 μg/L PFOS for 10 days, 8.8 and 82.5 ng/g dry weight (dw) PFOS were accumulated in leaves, respectively, and 150.9 and 1445.6 ng/g dw in roots, respectively·H2O2 was the dominant ROS in roots, while H2O2 and •O2- were detected in leaves. Impaired permeability of plasma membrane (58.7-88.7%, p < 0.05) and reduction in chlorophyll a (41.4-55.6%, p < 0.01) and b (38.4-41.3%, p < 0.01) were observed in leaves. The concentration of soluble proteins was elevated by 93.2-127.4% in roots (p < 0.05). Non-enzymatic antioxidants (glutathione, phenolics and carotenoids) were regulated to scavenge ROS in leaves, beside additional enzymatic antioxidants (ascorbate peroxidase, peroxidase, catalase and glutathione peroxidase) were activated in roots. Metabolomics revealed that some metabolites in primary (amino acids and carbohydrates) and secondary ((poly)phenols, terpenoids and benzylisoquinolines) metabolism were regulated, in accordance with the ROS scavenging process in plants. Our results demonstrated stress response and tolerance to PFOS were different in lettuce leaves and roots, and multiple defensive mechanisms in roots rendered high tolerance to PFOS.