Ioniță, Dunca, Radu 2026 — Plant responses to heavy metal stress in mining-impacted environments

Ioniță, Dunca, and Radu (Department of Environmental Engineering and Geology, and Department of Mechanical, Industrial and Transport Engineering, University of Petroșani, Romania; corresponding author Dunca) review the published evidence on the molecular and cellular mechanisms by which plants respond to chronic, multifactorial heavy metal stress in environments affected by mining activities (mine tailings, tailings ponds, flotation residues, acid mine drainage, ultramafic outcrops). The paper is a “Review” article in Plants (MDPI) covering 74 cited references, three schematic figures (Figure 1 mining-soil → root uptake → ROS/antioxidant defence framework; Figure 2 soil-root interface → ZIP/NRAMP/HMA transporters → vacuolar sequestration/cell-wall binding; Figure 3 redox imbalance and oxidative stress signalling axis), and seven synthesis tables (Table 1 metal-by-metal mining sources and cellular targets; Table 2 ZIP/NRAMP/HMA/ABC transporter comparison across acute vs chronic exposure; Table 3 strength-of-evidence matrix for absorption/transport mechanisms; Table 4 strength-of-evidence matrix for redox/antioxidant mechanisms; Table 5 seven detoxification mechanisms with primary cellular location and integration; Table 6 strength-of-evidence matrix for all seven mechanism families across laboratory / pot / field contexts; Table 7 conceptual differences between controlled experimental exposure and chronic mining exposure). The review reports no primary chemical, occurrence, or exposure measurements in any food, beverage, supplement, personal-care, or environmental matrix; its value to the wiki is conceptual background for the plant-side biology of metal uptake, translocation, chelation, and vacuolar sequestration as it bears on the remediation-evidence chapter, with a distinctive contribution in the form of explicit field-vs-laboratory evidence gradings for each mechanism family.

Why this matters

• It introduces a three-tier evidence classification (Class I controlled single-metal laboratory studies; Class II semi-controlled soil-based experiments; Class III field investigations under chronic polymetal exposure in mining environments) and applies that grading mechanism-by-mechanism in Tables 3, 4, and 6. The grading consistently shows “extensive” laboratory validation, “moderate” pot validation, and “limited” or “indirect” field validation across the seven canonical plant-tolerance mechanism families — making this the cleanest single source the wiki can cite for the “lab-to-field gap” framing that recurs in phytoremediation discussions.
• It anchors the mining-environment exposure context that distinguishes chronic polymetallic stress from the acute single-metal stress used in most mechanistic studies. Table 7 names twelve specific dimensions (exposure duration, metal composition, concentrations, chemical speciation, geochemical conditions, type of stress, dominant molecular responses, metabolic regulation, cellular compartmentation, phenotypic plasticity, ecological relevance, predictive capacity for field conditions) on which controlled experiments and mining-impacted environments differ — a useful framework when the wiki critiques laboratory-derived limits being extrapolated to natural exposure scenarios.
• It catalogues, in Table 1, the seven heavy metals most commonly associated with mining contamination (Cd, Pb, Zn, Cu, Ni, Cr-VI, As) with their typical mining sources, dominant mobility processes, major cellular and molecular targets, and predominant physiological/biochemical effects. The HMI-priority subset (Cd, Pb, As, Ni, Cr, Cr-VI) is fully covered; the non-HMI metals Cu and Zn are treated substantively but as ecological-priority rather than food-safety-priority metals.
• It documents the molecular-mechanism integration in Table 5: seven detoxification mechanisms (intracellular chelation via phytochelatins and metallothioneins; metal transport and compartmentalisation via HMA/ABC/CAX transporters; redox homeostasis regulation via SOD/CAT/APX/glutathione; gene expression modulation via transcription factors and stress-responsive genes; apoplastic immobilisation in cell-wall pectins; metabolic reprogramming of energy/nitrogen metabolism; phenotypic plasticity at the whole-plant level) with their primary cellular location and integration with other processes — the working vocabulary the wiki’s mitigation-evidence chapter draws on.
• It introduces specific population-level field evidence for chronic adaptation that goes beyond the more common acute-exposure framing: stable HMA4 overexpression in Arabidopsis halleri populations on Zn-rich mining soils (genomic amplification and constitutive expression, not transient induction); altered ROS-scavenging enzyme profiles in Silene vulgaris populations colonising polymetallic residues; comparative transcriptomic profiles of Noccaea caerulescens ecotypes from polymetallic mining areas showing constitutively activated metal-transporter networks vs uncontaminated populations. This population-genetics framing — that metallophyte populations under sustained selection pressure stabilise transcriptional profiles rather than relying on inducible responses — is the load-bearing concept the review uses to argue that laboratory acute-exposure models systematically under-predict adaptive capacity in chronically exposed populations.
• It documents the energy-cost framing of detoxification under chronic polymetallic stress: ATP-dependent vacuolar sequestration, PC synthesis, and HMA transporter activity carry sustained energy costs that may become limiting in nutrient-poor mining soils, favouring energy-conservative strategies such as apoplastic immobilisation or restriction of root-to-shoot translocation. This is a hedge against the naïve “more chelation = better tolerance” framing that the broader phytoremediation literature sometimes implies — closely parallel to the TaPCS1-Cd-sensitive rice finding documented in riyazuddin2022-heavy-metal-toxicity-sequestration-plants.

Key concepts and structure

The article has ten top-level sections plus references (74 entries). Section 1 (Introduction) frames heavy-metal stress as one of the dominant abiotic stressors in mining-impacted environments and notes that most current mechanistic knowledge derives from controlled experimental models rather than chronic polymetal field conditions. Section 2 (“Literature Search and Evidence Classification Strategy”) describes a structured narrative-synthesis approach using Web of Science Core Collection, Scopus, and PubMed with supplementary Google Scholar searches, focused on post-2000 literature with earlier foundational studies included where necessary; the Section 2.3 evidence classification (Class I / II / III) is the structural backbone of the strength-of-evidence tables. Section 3 (“Stress Caused by Heavy Metals in Mining-Affected Environments: Environmental Context”) catalogues the mining-source typology (tailings, tailings ponds, flotation residues, acid mine drainage, ultramafic outcrops) and the geochemical drivers (pH, redox potential, organic matter, ionic competition) that distinguish mining soils from natural or agricultural soils. Section 4 (“Absorption and Transport of Heavy Metals in Plants”) covers root-soil interface chemistry, the ZIP/NRAMP/HMA/ABC transporter families, long-distance xylem/phloem transport, and subcellular compartmentalisation, with Table 2 systematically contrasting acute vs chronic-exposure validation status by transporter family. Section 5 (“Cellular Toxicity and Redox Imbalance Induced by Heavy Metals”) covers ROS generation mechanisms, redox imbalance at the cellular level, the SOD/CAT/POD/APX antioxidant repertoire, glutathione dynamics, and the dual role of ROS as damaging agents and signalling molecules, with Table 4 grading lab vs pot vs field validation for five redox/antioxidant mechanisms. Section 6 (“Molecular Mechanisms of Detoxification and Tolerance in Plants Exposed to Heavy Metals”) covers chelation by phytochelatins and metallothioneins, vacuolar sequestration, cell-wall metal immobilisation, and integration of detoxification with tolerance; Table 5 summarises seven mechanism families with primary cellular location and integration with other processes. Section 7 (“Gene Expression and Stress Signalling Pathways in Response to Heavy Metal Exposure”) covers transcriptional regulation, transcription-factor families (bZIP19/bZIP23 for Zn, WRKY/MYB for Cd, NAC for oxidative stress and cell death), calcium-dependent signalling, MAPK cascades, and interaction between metal stress and other abiotic stresses, with Table 6 extending the lab/pot/field strength-of-evidence grading to all seven canonical mechanism families. Section 8 (“Connecting Mining-Affected Environments and Plant Molecular Responses”) synthesises Section 4–7 with Table 7 (twelve-dimension controlled-vs-chronic comparison) and the framing that chronic mining contamination acts as an environmental filter that stabilises specific molecular phenotypes in metallophyte populations. Section 9 (“Gaps in Knowledge and Future Research Directions”) names the lack of integrated soil-geochemistry × molecular-response studies, the dearth of longitudinal chronic-exposure transcriptomics, the under-application of multi-omics in field-relevant contexts, and the need for predictive molecular markers for phytostabilisation/phytoextraction suitability. Section 10 (Conclusions) closes with the framing that mining-environment metal stress must be analysed as a dynamic process integrating oxidative pressure, energy costs of detoxification, and metabolic trade-offs — not as a static toxicological dose-response.

Table 1 — Major heavy metals associated with mining activities and their primary molecular and cellular effects in plants (source p. 4, full transcription)

The seven mining-associated metals span the HMI HMTc priority subset (Cd, Pb, As, Ni, Cr-VI) plus the non-HMI ecological metals (Zn, Cu). The mobility column captures the geochemical determinant of bioavailability — central to the mining-environment framing because mobility shifts with pH and redox in ways that controlled-experiment dose metrics typically miss.

Table 2 — Comparative characteristics of major heavy-metal transporter families in acute and chronic exposure contexts (source p. 7, full transcription)

The Table 2 framing is the load-bearing methodological contribution of the paper: for each transporter family, the acute-exposure laboratory characterisation (column 4) is contrasted with the chronic mining-environment evidence (column 5). The pattern across all four families is the same — extensive laboratory characterisation, fragmentary field validation. The wiki should treat any quantitative transporter-expression claim derived from controlled experiments as conditional on field replication when applied to mining-context phytoremediation arguments.

Table 3 — Strength of evidence and status of environmental validation of the main molecular mechanisms involved in the adsorption and transport of heavy metals (source p. 10, full transcription)

The Table 3 grading (laboratory / pot experiments / field validation in mining operations / context of exposure validated / representative field examples) is applied across eight uptake-and-transport mechanism categories. The pattern: laboratory evidence is “extensive” or “strong” across all rows; pot evidence is “limited” to “moderate”; field validation is “limited” (ZIP, NRAMP), “documented” only in hyperaccumulators (HMA, xylem/phloem translocation, vacuolar sequestration, PC chelation, MT) or “well-documented in metallophytes” (root-to-shoot translocation restriction). Field validation is heavily concentrated on natural metallophyte populations rather than on the broader plant kingdom.

Table 4 — Strength of evidence for redox and antioxidant mechanisms in different exposure contexts (source p. 13, full transcription)

Five redox/antioxidant mechanism categories, graded across laboratory / pot / mining-field validation contexts. The pattern: laboratory evidence ranges from “extensive” (ROS overproduction, SOD/CAT activation, glutathione dynamics, redox signalling cascades) to “emerging” (long-term shifts in redox threshold); pot evidence is “moderate” to “limited”; field validation is “limited” (often indirect biomarkers), “variable”, “reported in metallophytes” (glutathione), “rare direct validation” (MAPK/Ca²⁺ cascades), or “hypothesised; limited field validation” (long-term redox threshold shifts).

Table 5 — Key molecular detoxification mechanisms contributing to heavy metal tolerance in plants (source p. 16, full transcription)

Seven detoxification mechanism families, each with key components, primary cellular location, functional role, and integration with other processes. This is the working vocabulary for the integrated-detoxification framing — none of these mechanisms function in isolation; tolerance emerges from their coordinated regulation.

Table 6 — Strength of evidence and validation status of key molecular mechanisms in different exposure contexts (source p. 19–20, full transcription)

Extends the Table 3/Table 4 lab-vs-field grading to seven mechanism families spanning the full uptake → defence → tolerance pathway. Field validation is concentrated on metallophyte populations and remains “limited”, “indirect”, or “sporadic” across most rows; “stable overexpression of HMA4 in Arabidopsis halleri” is the cleanest field example, with chronic N. caerulescens transporter-network activation and chronic phytochelatin accumulation in field-collected metallophytes as second-tier confirmations.

Table 7 — Key conceptual differences between controlled experimental metal exposure and chronic exposure in mining-impacted environments (source p. 21, full transcription)

Twelve dimensions on which controlled experiments and chronic mining exposure differ. This is the wiki’s cleanest single-source citation for the “lab-derived dose-response models extrapolate poorly to mining-impacted field exposures” framing — load-bearing wherever the wiki discusses the gap between EFSA/JECFA TDI/PTWI/PTMI values (which themselves rest on controlled-exposure toxicology) and the chronic-exposure realities of contaminated agricultural soils.

Mining-environment geochemical context (source Section 3, p. 3–5)

Mining environments are characterised by extreme pedological and geochemical properties (extremely low or high pH, redox potential fluctuations, low organic matter content, unstable physical structures) that amplify the stress on plants beyond what natural or agricultural soils typically present. Acidic and oxidising conditions increase the mobility and bioavailability of Cd²⁺ and Zn²⁺; reducing conditions can temporarily immobilise metals but leave them susceptible to remobilisation following environmental changes. Variability in redox potential alters the valence states of redox-active metals (Fe, Cu), influencing intracellular ROS generation. Plants in such environments face simultaneous exposure to complex metal mixtures rather than single elements, with metal-metal interactions (competition for membrane transporters, intracellular binding sites, regulation of stress-related gene expression) that significantly alter biological responses compared to single-metal exposure. The presence of essential metals in excessive concentrations can induce nutritional imbalances, further exacerbating physiological stress.

Root absorption and metal transporter machinery (source Section 4, p. 5–9)

Metal absorption at the root-soil interface occurs mainly through membrane transport systems physiologically dedicated to nutrient acquisition. Essential metals (Cu, Zn, Ni) can become toxic in excess; non-essential metals (Cd, Pb) exploit the same transport pathways due to chemical similarity to nutrient ions. Absorption is modulated by rhizosphere pH, cellular redox potential, and microbiological activity — under acidic or oxidising conditions, metal flux to root cells increases. ZIP (ZRT/IRT-like) proteins transport Zn²⁺, Fe²⁺, Mn²⁺ and facilitate excess-condition uptake of other metals; NRAMP proteins handle cellular and intracellular bivalent-metal redistribution; HMA P-type ATPases mediate ATP-dependent active translocation across membranes for both long-distance transport to aerial parts and vacuolar sequestration. Chronic mining exposure stably alters HMA expression in metallophyte populations (HMA4 genomic amplification and constitutive overexpression in A. halleri on Zn/Cd-rich soils; comparative transcriptomic activation of metal-transporter networks in N. caerulescens ecotypes from polymetallic mining areas). After absorption, metals can move to aerial organs via the xylem either free-ionic or complexed with organic ligands; chronic-exposure plants may exhibit adaptive restriction of root-to-shoot translocation (a phytostabilisation-associated trait). Subcellular compartmentalisation — sequestration in vacuoles, binding to phytochelins or metallothioneins, association with cell wall — is fundamental for limiting metal interaction with mitochondria and chloroplasts; in mining environments with continuous multimetal exposure, compartmentalisation becomes a long-term homeostatic adaptation rather than an acute response.

ROS generation, redox imbalance, and antioxidant defence (source Section 5, p. 10–13)

Heavy metals stimulate ROS generation through multiple mechanisms — interference with electron transport chains in mitochondria and chloroplasts, activation of cyclic redox reactions, disruption of electron transfer in respiratory and photosynthetic complexes — producing superoxide radicals, hydrogen peroxide, and hydroxyl radicals. In mining environments, ROS generation becomes a persistent process; sustained ROS production acts as both direct toxicity and as a signal triggering cellular defence responses. Acidic pH increases Cd²⁺ and Zn²⁺ mobility, raising cellular oxidative pressure; fluctuating redox potential can temporarily immobilise metals followed by episodic remobilisation that generates oxidative bursts — dynamic exposure patterns rarely replicated in hydroponic systems.

Redox homeostasis is maintained by SOD, CAT, peroxidases, and the glutathione system; glutathione participates in both ROS detoxification and PC synthesis for metal chelation. Acute exposure produces rapid antioxidant activation; chronic polymetallic exposure may cause stable adjustments of redox thresholds and ROS-dependent gene regulation. Brassica juncea exposed to Cd exhibits increased SOD and CAT under controlled conditions; A. halleri populations on Zn-rich mining substrates show enhanced glutathione-dependent antioxidant capacity associated with chronic exposure and long-term adaptation; Silene vulgaris populations on polymetallic residues show altered ROS-scavenging enzyme profiles compared to uncontaminated populations. ROS function dually as damage agents (membrane lipid peroxidation, protein oxidation, nucleic acid damage) and as signalling molecules; sustained oxidative stress under chronic exposure can recalibrate redox signalling thresholds, altering the amplitude and sensitivity of ROS-dependent transcriptional responses.

Phytochelatins, metallothioneins, and integrated detoxification (source Section 6, p. 14–16)

Phytochelatins are cysteine-rich peptides enzymatically synthesised from glutathione in response to heavy-metal exposure; they chelate Cd, Pb, Cu, Zn and reduce free cytosolic metal-ion concentrations. Cd tolerance specifically integrates phytochelatin synthesis, metallothionein induction, antioxidant activation, and transporter-mediated sequestration; the efficiency of tolerance depends on the balance between cytosolic chelation, vacuolar compartmentalisation, root-to-shoot translocation restriction, and redox homeostasis maintenance. Recent transcriptomic and multi-omic analyses identify Cd tolerance as a property of integrated defence networks involving stress-responsive genes, thiol metabolism, ROS signalling, and metal transporter expression — networks that must remain stable under long-term environmental pressure in mining environments. Metallothioneins play a dual role in essential-metal homeostasis and toxic-metal detoxification; their tissue-specific distribution suggests distinct functions in cellular protection, and their coordinated action with phytochelatins enhances the flexibility and efficiency of detoxification responses under multi-metal exposure. In mining environments characterised by persistent exposure to multiple metals and nutritional imbalance, chelation capacity alone may be insufficient without coordinated sequestration and metabolic adjustment; field evidence from metallophyte populations suggests chelation efficiency interacts with transporter regulation and compartmentalisation rather than functioning as an isolated mechanism. The cell wall (polysaccharides, pectins, functional groups capable of binding cations) acts as a passive barrier and an adaptive component — under chronic stress, cell-wall structure and composition may undergo metal-binding-capacity-enhancing adjustments; apoplastic immobilisation represents an energy-conserving tolerance strategy compared to ATP-dependent intracellular sequestration, particularly advantageous for phytostabilising species on nutrient-poor substrates.

Gene expression, transcription factors, and signalling pathways (source Section 7, p. 17–18)

Heavy-metal stress significantly alters gene expression profiles, affecting genes involved in metal transport, detoxification, antioxidant metabolism, and hormonal regulation; activation or repression is controlled by transcription factors sensitive to redox status and metal-accumulation signals. Prolonged exposure can establish stabilised expression patterns associated with tolerance — transporters, antioxidant enzymes, and chelation/compartmentalisation proteins frequently upregulated. Cd stress is a particularly clear case where transcriptional regulation coordinates metal transport, thiol-mediated detoxification, antioxidant responses, and long-term adaptation. The transition from inducible acute responses to semi-constitutive regulatory configurations may reflect evolutionary adaptation of metallophyte populations to persistent metal pressure; longitudinal field studies confirming this transition remain limited. Transcription-factor families implicated include bZIP (bZIP19/bZIP23 for Zn deficiency/excess and metal homeostasis), WRKY and MYB (Cd-induced stress signalling and antioxidant regulation), and NAC (oxidative stress and programmed cell death modulation in prolonged exposure). Most functional characterisation derives from overexpression or knockout studies in laboratory model species; direct evidence for differential transcription-factor regulation in mining-site field populations remains scarce.

Cellular signalling under metal stress involves calcium-dependent pathways (transient intracellular Ca²⁺ increases activate protein kinase cascades), MAPK signalling (integration of metal-derived signals with other abiotic stress signals), and redox-sensitive mechanisms. These signalling pathways are well characterised under controlled conditions but their long-term dynamics under chronic polymetallic exposure remain poorly documented at the ecosystem level. Metal stress interacts with other abiotic stresses (drought, salinity, extreme temperatures); the cellular redox state plays a central role in mediating these interactions. In mining environments where metal stress is rarely singular and frequently combined with water deficit, nutritional imbalance, and salinity, the ability to integrate multiple signals and flexibly adjust molecular responses is essential for survival.

Conceptual integration and phytoremediation implications (source Sections 8–9, p. 20–23)

Controlled experimental exposure mainly captures early signalling events and transient molecular activation; mining environments favour stable and adaptive reconfiguration of molecular networks. The review identifies four short-term research priorities (systematic field validation of ZIP/HMA/NRAMP transporters in plants naturally growing on mining sites; direct in situ assessment of intracellular ROS dynamics under fluctuating geochemical conditions; integration of soil geochemical profiling with molecular and transcriptomic analyses), four medium-term directions (longitudinal transcriptomic monitoring of chronically exposed populations; applying integrated multi-omic approaches in field-relevant exposure scenarios; investigation of epigenetic mechanisms contributing to metal-tolerance stabilisation; quantifying energy trade-offs associated with sustained detoxification and antioxidant activity), and three long-term strategic objectives (predictive molecular markers for phytostabilisation/phytoextraction suitability; incorporation of molecular stress indicators into ecological risk assessment frameworks; interdisciplinary monitoring systems linking molecular diagnosis with environmental geochemistry).

Phytoremediation implications: molecular traits such as restricted root-to-shoot translocation, enhanced vacuolar sequestration, efficient antioxidant regulation, and stable transcriptional reprogramming under chronic exposure are particularly relevant for phytostabilisation. Mechanisms associated with controlled long-distance transport and metal chelation favour phytoextraction strategies, albeit with increased ecological risk. The effectiveness of phytoremediation cannot be reliably predicted from laboratory molecular responses alone — site-specific environmental assessment must be integrated with molecular screening.

Methods (brief)

This is a structured narrative-synthesis review article. The authors describe a literature-search strategy (Web of Science Core Collection, Scopus, PubMed, supplementary Google Scholar) focused mainly on post-2000 plant molecular biology, redox regulation, and environmental geochemistry, with earlier foundational studies included for context. Reference management used Zotero for duplicate removal and thematic categorisation. Search-term combinations included “heavy metal stress”, “mining soils”, “metal homeostasis”, “reactive oxygen species”, “phytochelatins”, “metallothioneins”, “multi-metal exposure”, and “plant adaptation” applied with Boolean operators. Study-selection criteria specified peer-reviewed research articles or high-quality reviews addressing molecular, cellular, physiological, or geochemical aspects of plant responses to heavy-metal or metalloid exposure; particular attention was given to studies investigating redox regulation, ROS signalling, antioxidant systems, metal transport and homeostasis, thiol-mediated detoxification, and adaptive responses under chronic polymetal exposure in mining environments. Both controlled laboratory experiments and field investigations were considered. Studies lacking clearly defined exposure conditions or not assessing plant responses were excluded. The Class I (controlled single-metal laboratory) / Class II (semi-controlled soil-based) / Class III (chronic polymetal mining-site field) evidence classification is the structural backbone of the strength-of-evidence tables (Tables 3, 4, 6); given the heterogeneity of experimental designs and exposure scenarios, an integrative conceptual synthesis rather than statistical aggregation was adopted. The article was received 31 January 2026, revised 7 March 2026, accepted 25 March 2026, and published 28 March 2026 in Plants 2026, Vol 15, Article 1045 (DOI 10.3390/plants15071045). Academic Editors: Krzysztof Sitko, Antonio Scopa. Funding: no external funding. Author Contributions: Conceptualization M.F.I. and E.C.D.; investigation M.F.I.; formal analysis M.F.I.; writing — original draft M.F.I.; writing — review and editing E.C.D. and S.M.R.; validation S.M.R.; supervision E.C.D.; project administration M.F.I. Data Availability: no new data created or analysed. Conflicts of interest: none declared. The journal (MDPI) is open access; the article is published under CC BY 4.0. The 74-reference set spans 2000 (Kabata-Pendias, Trace Elements in Soils and Plants, CRC Press) to 2026 (Xie et al. centennial Pb-Zn mining pollution paper in Ecotoxicology and Environmental Safety), with concentration in environmental science (Environmental Pollution, Science of the Total Environment, Environmental Science and Pollution Research, Journal of Environmental Management, Ecotoxicology and Environmental Safety) and plant physiology/molecular biology (Plants, Plant Cell Reports, Plant Physiology and Biochemistry, Annual Review of Plant Biology, Trends in Plant Science, Bioresources and Bioprocessing). Notable self-citations: refs [23] (Ionita et al. 2024 case-study Balomir-Uricani Tailings Dump phytoremediation paper in Sci. Study Res. Chem. Eng. Biotechnol. Food Ind.) and [26] (Ionita et al. 2025 IntechOpen chapter Mining Activities–Mediated Soil Contamination with Heavy Metals).

Implications

• Certification: The review contributes no occurrence data and no exposure data, so it does not move any HMTc threshold-setting work. Its value for HMTc is indirect — the Table 7 twelve-dimension framework for distinguishing controlled-experimental from chronic-mining exposure is methodologically useful when HMTc engages with EFSA/JECFA toxicology that itself rests on controlled-exposure dose-response models; the wiki’s framing of regulatory cap derivations should acknowledge the lab-vs-field gap that this paper documents systematically for plant biology and that applies in modified form to human-exposure toxicology as well. The review’s mining-environment framing is also indirectly relevant to crops grown on legacy mining-contaminated agricultural land, where soil-pH and redox heterogeneity may produce occurrence variability that pooled-percentile thresholds based on bulk-soil concentration alone cannot capture.
• App: No routing to ingredient or product pages. The review provides background reading for cadmium, lead, arsenic, nickel, chromium, chromium-hexavalent, and remediation-evidence on plant-side biology of metal uptake and chelation in chronic mining-exposure contexts; it does not bear on contamination occurrence in any specific food or personal-care matrix.
• Courses: Useful as a single-source orientation to the seven-mechanism integrated-detoxification framework (Table 5), to the lab-vs-pot-vs-field strength-of-evidence grading methodology (Tables 3, 4, 6), and to the controlled-vs-chronic-mining conceptual framework (Table 7). Should not be cited as the authority for any specific quantitative crop-level HM-reduction claim; trace claims to the cited primary studies first (e.g., the HMA4-overexpression-in-A. halleri claim attributed to ref [31] Huguet et al. 2012 Environmental and Experimental Botany, or the N. caerulescens polymetallic-ecotype claim attributed to ref [17] Krämer 2010 Annual Review of Plant Biology).
• Microbiome: Minimally relevant. The review mentions rhizosphere microbiological activity as a modulator of metal absorption but does not engage the gut microbiome or the heavy-metal-microbiome exposure axis. WikiBiome federation is unlikely to draw on this source.

Limitations

This is a structured narrative review with a declared search strategy but no PRISMA flow, no risk-of-bias assessment, and no quantitative synthesis. The 74-reference set is small for a review covering the full plant molecular-stress-response literature and shows concentration on European (especially Romanian, Italian, Spanish) environmental-engineering and Asian plant-physiology journals; the review’s emphasis on mining environments rather than the broader phytoremediation or food-safety literature limits its applicability outside the mining-soil-contamination context. The two Ionita-coauthored self-citations (refs [23], [26]) carry minor risk of perspective concentration — both are subsequent or prior Ionita-group publications on phytoremediation of specific Romanian tailings (Balomir-Uricani) — but neither is used to anchor a load-bearing quantitative claim. Quantitative dose-response data are absent: the strength-of-evidence tables grade evidence as “extensive”, “moderate”, “limited”, or “indirect” without specifying concentration ranges, sample sizes, or effect sizes; the review is unsuitable for any synthesis page that requires effect-size estimates. The metals covered span both HMI-priority analytes (Cd, Pb, As, Ni, Cr-VI) and non-HMI essential/non-essential metals (Cu, Zn); As is treated under the general label without iAs vs tAs distinction, Cr and Cr-VI are distinguished only in Table 1; MeHg vs tHg does not appear because Hg is not in the mining-metals focal set (sulphide-rich tailings notwithstanding, the review’s seven-metal focus excludes Hg). The transcription of Tables 2 and 3 preserves source-language inconsistencies and OCR artifacts (e.g., “Validation direct limited; inferred in the case of metallophytes”, “Confirmation sporadic direct confirmation in the field”, “Root retention strategies in vegetation in areas settling areas”) that reflect post-translation editing rather than intentional terminology choices; the wiki preserves the source’s vocabulary verbatim. One exception: Table 5 row 1 (“Key Components”) cell — the source PDF reads “Phytoquelatins, metallothioneins” but the wiki transcribes “Phytochelatins, metallothioneins”. The “Phytoquelatins” form appears throughout Section 6 of the source PDF interchangeably with “Phytochelatins”, and the source’s own Abbreviations list (PDF p. 24) defines PC = Phytochelatin; the wiki normalises to the chemically correct “Phytochelatins” since the alternative form is an OCR/translation artifact rather than an intentional terminology distinction.

Wiki pages this source may touch

• cadmium
• lead
• arsenic
• nickel
• chromium
• chromium-hexavalent
• remediation-evidence

Verification notes

Existing-page check. DOI grep (10.3390/plants15071045), raw_handle grep (MFK_13-molecular-and-cellular-mechanisms-of-plant-resp), and cite-key glob (ionita*) over wiki/sources/ on 2026-06-08 returned no matches. This is a NEW source page — no prior version to merge-enhance.

Evidence tier. B (secondary narrative review with declared search strategy but no PRISMA / no risk-of-bias / no quantitative synthesis). The paper reports no primary measurements and uses a qualitative strength-of-evidence grading rather than meta-analytic pooling. A-tier is reserved for primary peer-reviewed studies and authoritative agency monographs; this is a structured narrative integration.

Metals frontmatter. [Cd, Pb, tAs, Ni, Cr, Cr-VI] per the HMTc 10-analyte priority list, scoped to the seven mining-metals focal set in Table 1. Cd is the dominant subject (Table 1 row 1, phytochelatin/Cd-tolerance integration discussion in Section 6, Cd transcriptional-regulation case study in Section 7). Pb is treated in Table 1 (sulphide-rich mining wastes, low-mobility root accumulation, Ca-metabolism interference) but receives less mechanistic depth than Cd. As is treated in Table 1 (phosphate-transport-system interference, oxidative stress) without iAs vs tAs speciation distinction, so tAs is the appropriate broad label. Ni is treated in Table 1 (ultramafic-rock source, nitrogen-metabolism disruption) and in the context of Alyssum hyperaccumulators implicitly via the metallophyte-population framing. Cr is treated in Table 1 (industrial-mining wastes); Cr-VI is explicitly distinguished in Table 1 (high mobility under oxidising conditions, DNA-targeting genotoxicity, severe oxidative stress) and in the Cr(III) → Cr(VI) oxidation framing, so both Cr and Cr-VI are listed. Cu, Zn are discussed substantively (Table 1, transporter sections) but are not on HMI’s 10-analyte priority list and are not in frontmatter; the wiki’s metals/copper.md and metals/zinc.md (Zn not in current list per directory; copper.md exists) do not currently serve as HMTc analyte pages. Hg, MeHg, Al, Sn, Sb, U do not appear in the source. Per the HMI convention precedent in riyazuddin2022-heavy-metal-toxicity-sequestration-plants and luo2024-peptides-heavy-metal-remediation, a multi-metal review carries the in-scope HMI analyte set in frontmatter rather than a single dominant metal.

Ingredients, products, matrices, jurisdictions frontmatter. All empty. The source measures nothing in any food matrix. The plant species named — Arabidopsis halleri, A. thaliana, Noccaea caerulescens, Brassica juncea, Silene vulgaris, Hibiscus cannabinus — appear as metallophyte/hyperaccumulator field-study subjects or laboratory model organisms in genetics/phenotype contexts, not as sampled food commodities with reported HM concentrations. No national regulatory framework or occurrence dataset is engaged; the institutional affiliation is University of Petroșani (Romania), which sits in a region historically associated with coal and metal mining (Jiu Valley), but the review’s framing is conceptually international. jurisdictions: remains empty.

Sample size. Null. The narrative has no sampling frame; the review summarises ~74 primary and secondary studies but does not aggregate their sample sizes. sample_n represents the latter and is null here.

Brand firewall (Part 12). No commercial food, supplement, or personal-care brand names appear in the source body for contamination values. The methods commentary does not invent analytical instruments or LODs (none are reported, since no primary measurements are made). No firewall action required.

HMTc firewall (Part 2). The review contains no HMTc-threshold language, no claims about HMI certification levels, and no consumer-audience risk advisories. The Section 9 “Future Research Directions” framing includes forward-looking proposals (predictive molecular markers for phytostabilisation/phytoextraction suitability; incorporation of molecular stress indicators into ecological-risk-assessment frameworks; interdisciplinary monitoring systems linking molecular diagnosis with environmental geochemistry) — these are research-agenda framings for the ecological-restoration and phytoremediation communities, not HMTc threshold proposals, and are preserved in the Implications section without escalation. The Table 7 controlled-vs-chronic conceptual framework is methodologically relevant to the wiki’s framing of regulatory toxicology limits (which rest on controlled-exposure dose-response) but the wiki’s own framing of that gap is not introduced or modified here. No firewall action required.

Date arithmetic. Received 31 January 2026, revised 7 March 2026, accepted 25 March 2026, published 28 March 2026 — all consistent with the year: 2026 frontmatter. The journal issue Plants 2026, Vol 15, Article 1045 carries 2026 as the publication year. DOI 10.3390/plants15071045 resolves to Plants 2026, Vol 15, Article 1045.

Reviewer’s note on scope fit. This paper is in the “Black Market Peptide Metal Survey / heavy_metals_peptides” Manual Fetch Kimi folder alongside luo2024-peptides-heavy-metal-remediation, riyazuddin2022-heavy-metal-toxicity-sequestration-plants, marques2025-phytochelatins-cadmium-mitigation, ruttkay-nedecky2013-metallothionein-oxidative-stress, and the Zhang/Metalorian de novo peptide design paper. Per the 2026-06-02 commit 3f47f95 — scope: mitigation/remediation is in-scope, not a skip, peptide-mediated mitigation/remediation papers are in scope as background for the mitigation-evidence chapter. This paper’s distinctive contribution within the folder set is the explicit lab-vs-pot-vs-field strength-of-evidence grading methodology (Tables 3, 4, 6) and the controlled-vs-chronic conceptual framework (Table 7); the other peptide-axis papers in the folder are more narrowly focused on specific chelation pathways (Marques on Cd/PC; Ruttkay-Nedecky on mammalian MT/oxidative stress) or general taxonomy (Luo on peptide-metal remediation; Riyazuddin on multi-mechanism plant tolerance). The phytochelatin/metallothionein peptide axis — the reason the Kimi agent grouped these papers — is treated in Section 6 (PC/MT chelation integration) and Table 5 row 1 (intracellular chelation by phytochelatins and metallothioneins in cytosol/vacuole).

Slug-vocabulary note. [[mitigation/remediation-evidence]] exists at wiki/mitigation/remediation-evidence.md (verified by directory listing). [[metals/cadmium]], [[metals/lead]], [[metals/arsenic]], [[metals/nickel]], [[metals/chromium]], [[metals/chromium-hexavalent]] all exist at corresponding paths under wiki/metals/. No invalid slugs.

Speciation note. The source uses “As” and “Cr” without consistent speciation. Cr(VI) appears in Table 1 row 6 (high mobility under oxidising conditions, DNA-targeting genotoxicity); Cr(III) appears in the Cr(III) → Cr(VI) oxidation source-pathway framing. As is treated as a single category in Table 1 (phosphate-transport-system interference); the review does not distinguish AsIII vs AsV at the molecular-mechanism level. Per the HMI convention, the broad tAs label is applied in frontmatter; Cr and Cr-VI are both listed where the source distinguishes them, and the wiki’s prose preserves the source’s vocabulary verbatim.

Audit subagent (2026-06-08) verdict: PROMOTE. Five checks (numerical fidelity, slug vocabulary, speciation/methods, brand firewall, HMTc firewall) returned five ✅ with one ⚠️ on numerical fidelity Table 5 row 1 cell normalization, plus one minor framing-clarity note on the reference-span endpoints attribution. The Table 5 normalization (source PDF “Phytoquelatins” → wiki “Phytochelatins”) is verified against PDF Section 6 body and the Abbreviations list (PDF p. 24, PC = Phytochelatin) as an OCR/translation artifact rather than intentional terminology, and a one-line transcription note has been added to the Limitations section disclosing the normalization. The reference-span framing note (the “2000 (Kabata-Pendias) to 2026 (Xie et al.)” rhetorical framing in the Methods (brief) section implies bibliographic first/last when these are actually refs [49] and [21] respectively) is acknowledged but no correction applied — the span endpoints are factually correct and the framing is interpretive rather than misleading. All seven tables (Tables 1–7) verified row-by-row against PDF pages 4, 7, 10, 13, 16, 19–20, 21. DOI, authors, date arithmetic, 74-reference count, self-citation attributions (refs [23], [26]), HMA4-in-A. halleri primary attribution (ref [31] Huguet et al. 2012), and N. caerulescens primary attribution (ref [17] Krämer 2010 Annu. Rev. Plant Biol.) all verified. All wikilink slugs (metals/cadmium, metals/lead, metals/arsenic, metals/nickel, metals/chromium, metals/chromium-hexavalent, mitigation/remediation-evidence) verified present in the wiki. Brand firewall (Part 12) and HMTc firewall (Part 2) both clean — no commercial brand names, no threshold language, no over-strengthening of field-validation claims relative to the source’s own “extensive lab / limited field” evidence-grading framing. 1 finding flagged, 1 cleanup applied (Table 5 transcription note), 0 rejected. Audit subagent ID a383b648647ab5385.

Page history

The five most recent substantive edits to this page. The full version history lives in git; when DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.