Plants in Polluted and Disturbed Environments: Phytoremediation, Emerging Contaminants and Soil–Plant–Microbe Interactions

Phytoremediation of Contaminated Soils: Fundamental Principles, Mechanisms, Applications and Future Perspectives

Shweta Nag — 2026-11-13

Soil contamination by potentially toxic elements, petroleum-derived compounds and persistent synthetic chemicals creates hazards that cannot be addressed adequately by a single remediation technology. Phytoremediation uses plants and their associated microorganisms to extract, immobilise, transform or help degrade contaminants while maintaining vegetative cover. Its appeal rests on low physical disturbance and potential restoration of soil functions, but mechanistic capacity under controlled conditions does not necessarily predict defensible risk reduction in heterogeneous field soils. This critical narrative review integrates plant physiology, rhizosphere biogeochemistry, field performance, implementation economics and emerging contaminants. Literature published from 2000 to 1 September 2026 was considered, alongside seminal earlier work where needed; peer-reviewed experimental studies and well-supported syntheses were appraised for evidence–outcome alignment, field relevance and limitations. The strongest evidence supports site-specific phytoextraction of selected elements, particularly arsenic and cadmium, and vegetative stabilisation of contaminated mine substrates. Yet metal removal is constrained by contaminant inventory, biomass yield, sorption and time, while reductions in extractable concentrations may represent immobilisation rather than elimination. Plant-assisted degradation of petroleum hydrocarbons is supported by promising trials but remains difficult to separate from microbial biostimulation and background attenuation. For per- and polyfluoroalkyl substances, plant uptake is increasingly documented, whereas complete destruction and safe biomass treatment are less securely established. Amendments, microbial inoculants and molecular approaches can improve selected processes but may also shift exposure pathways or reduce extractive uptake. An integrated decision framework is proposed in which contaminant mass balance, exposure reduction, plant survival, ecological safeguards, land-use requirements and long-term monitoring determine whether extraction, stabilisation, rhizodegradation or a hybrid remedy is justified. Future progress requires replicated field trials, transparent contaminant accounting, validated biomass-treatment chains and consistent comparison with alternative remediation strategies.

Plants in Polluted and Disturbed Environments: Physiological Responses, Ecological Adaptations and Restoration Strategies

Shweta Nag — 2026-11-13

Pollution and physical disturbance alter plant performance through interacting chemical, hydrological, biological and demographic filters. Yet the capacity of plants to survive in degraded environments is often treated as evidence of ecological recovery or contaminant remediation, despite important differences between tolerance, establishment, pollutant retention, risk reduction and ecosystem function. This critical narrative review integrates plant stress physiology, community ecology and restoration science to examine how these distinctions affect interpretation and management. Literature published principally from 2000 to 1 September 2026 was evaluated using accessible scholarly indexes, original field investigations, mechanistic experiments, syntheses and ecological restoration standards. The review considers metal(loid)-contaminated soils, altered salinity and nutrient regimes, atmospheric ozone, selected organic contaminants and microplastics, alongside mining, land clearance, fire and other disturbances. Physiological responses include ion homeostasis, antioxidant regulation, photosynthetic adjustment, resource allocation and stress signalling. Their ecological significance depends on exposure duration, trait variation, life-history strategy, plant–soil feedbacks and the availability of colonists. Evidence for particular biochemical pathways is often stronger than evidence that the same mechanisms deliver persistent field-scale remediation. Similarly, vegetation cover may suppress erosion without lowering contaminant mobility or restoring native community composition. Natural regeneration, phytostabilisation, assisted revegetation, constructed wetlands and climate-aware species selection each have context-dependent benefits and limitations. The strongest restoration programmes therefore establish separate benchmarks for exposure reduction, vegetation persistence, biodiversity, soil functioning and downstream risk, and test potential conflicts among them. Priority needs include multi-stressor experiments linked to field gradients, replicated long-term comparisons of restoration pathways, explicit contaminant mass balances, and monitoring designs capable of distinguishing ecological recovery from superficial greening. An integrated, risk-sensitive framework can improve decisions without presuming that one tolerant species or technology is universally suitable.

Phytoextraction of Toxic Metals and Metalloids from Contaminated Soils: Mechanisms, Plant Selection and Environmental Applications

Shweta Nag — 2026-11-13

Phytoextraction is frequently presented as a low-impact option for contaminated land, yet impressive shoot concentrations do not necessarily translate into meaningful reductions in soil contaminant inventories or exposure. This critical narrative review examines the physiological, edaphic and operational conditions under which plant-mediated removal of potentially toxic metals and metalloids can constitute defensible remediation. Relevant scholarly literature published from 1998 to 1 September 2026 was identified through accessible multidisciplinary, environmental and agricultural information sources, supplemented by citation-oriented searches. Mechanistic evidence was interpreted alongside greenhouse studies, repeated-harvest trials and field applications, with particular attention to differences between contaminant uptake, harvested removal and risk reduction. Three interacting constraints emerge: replenishment of the phytoavailable pool from soil solids; the trade-off between shoot concentration, biomass production and repeated-harvest persistence; and the capacity to contain, process and account for contaminated biomass without transferring hazards elsewhere. Cadmium and zinc extraction by selected hyperaccumulators, arsenic extraction by Pteris vittata, and nickel recovery on suitable ultramafic substrates have comparatively substantial experimental support, although field outcomes vary with soil chemistry, climate, depth and management. Lead removal remains especially constrained by low mobility and the secondary risks of chemical mobilisation. Molecular and microbial interventions reveal plausible improvements, but their translation to durable field performance is uncertain. The strongest assessment of success combines independently verified harvest fluxes and soil inventories with bioavailability, exposure indicators, ecological impacts and full biomass management. Phytoextraction should consequently be treated neither as universally benign land restoration nor as intrinsically ineffective because total soil concentrations decline slowly. Its value depends on clearly defined endpoints, carefully matched plant–soil combinations, long-term monitoring and explicit treatment of residual risks. Future work should prioritise controlled field comparisons, defensible mass balances, food-chain protection and transparent life-cycle accounting.

Phytodegradation of Organic Pollutants: Plant Metabolism, Enzymatic Transformation and Environmental Detoxification

Shweta Nag — 2026-11-13

Organic pollutants released through agriculture, industry, municipal wastewater and contaminated-site legacies can enter vegetation, but their disappearance from environmental compartments does not necessarily demonstrate their destruction by plants. This critical narrative review examines how exposure, uptake, enzymatic transformation, conjugation and sequestration determine the fate of organic contaminants within terrestrial and wetland plants. Literature published from 1992 to 1 September 2026 was assessed, with earlier foundational studies retained where necessary. Evidence from mechanistic plant experiments, isotopic tracing, transformation-product analysis, engineered systems and field studies was interpreted according to its capacity to distinguish direct plant metabolism from microbial degradation, physical retention and volatilisation. The established three-phase model of plant xenobiotic metabolism explains many reactions involving cytochrome P450 monooxygenases, hydrolases, glutathione transferases, glycosyltransferases and transport proteins, but it does not imply complete mineralisation or toxicological safety. Research on trichloroethylene, selected herbicides, pharmaceuticals and chlorinated aromatics demonstrates compound- and species-dependent transformation. Isotope-labelled studies reveal substantial non-extractable residues, whereas field comparisons show that enhanced enzymatic capacity may not translate into proportionate contaminant removal. In constructed wetlands and petroleum-contaminated soils, plant-associated microbiota frequently contribute substantially to treatment, complicating attribution to plant metabolism. Transformation products in edible tissues, remobilisation of bound residues and emissions of volatile contaminants remain under-assessed. The review proposes an evidence hierarchy linking molecular mechanism, contaminant mass balance and effect-based toxicity to field-scale outcomes. Future research should prioritise realistic exposure conditions, causal separation of plant and microbial pathways, long-term product tracking and transparent assessment of ecological trade-offs. Phytodegradation is consequently best regarded as a conditional component of remediation rather than a general synonym for pollutant elimination.

Emerging Contaminants in Soil–Plant Systems: Uptake, Toxicity, Bioaccumulation and Ecological Risks of Microplastics, PFAS and Pharmaceutical Residues

Shweta Nag — 2026-11-13

Agricultural soils receive chemically and physically dissimilar contaminants through wastewater irrigation, organic amendments, atmospheric deposition and agricultural materials. Microplastics and nanoplastics, per- and polyfluoroalkyl substances (PFAS), and pharmaceutical residues increasingly coexist in soil–plant systems, yet are commonly assessed within separate disciplinary frameworks. This critical narrative review examines their sources, environmental availability, root interactions, internal transport, toxicity, bioaccumulation and implications for soil ecological function and food-chain exposure. Peer-reviewed field studies, controlled experiments, methodological evaluations and quantitative evidence syntheses published between 2006 and 1 September 2026 were considered through targeted scholarly searching and citation checking. A central distinction emerges between contamination, biologically available exposure, verified internal accumulation, adverse effect and demonstrated ecological risk. Nanoplastic uptake has been shown experimentally, but its field-scale importance remains difficult to establish because of particle-characterisation and tissue-localisation challenges. For PFAS, compound-specific sorption and plant-part distribution govern crop transfer; shorter-chain compounds often move more readily to shoots, although field observations include non-detections and substantial crop-to-crop variability. Pharmaceuticals display pronounced dependence on ionisation, soil organic matter, irrigation practice and in-plant transformation, with metabolites complicating exposure assessment. Microplastic effects on soil structure and microbial processes are plausible and experimentally supported, whereas attribution of field-level production losses to realistic particle exposures remains less secure. Antibiotic residues introduce the additional concern of selection pressure on soil resistance determinants. Evidence for interactions among these contaminant classes is mechanistically plausible but insufficient to support a general claim that microplastics consistently increase chemical bioavailability or toxicity. The review develops an exposure-to-effect framework and identifies priorities for paired field monitoring, validated analytical methods, realistic mixture experiments and crop-specific risk assessment. A precautionary but proportionate management approach should protect the benefits of water and nutrient reuse while reducing avoidable contaminant inputs and addressing uncertainties in chronic ecological exposure.

Rhizosphere Engineering for Enhanced Phytoremediation: Plant–Microbe Interactions, Root Exudates and Microbiome-Based Strategies for Polluted Soils

Shweta Nag — 2026-11-13

Phytoremediation can restore vegetation and moderate exposure to soil contaminants, yet its effectiveness often depends on processes occurring within a small, chemically dynamic volume of root-influenced soil. Rhizosphere engineering seeks to direct these processes by selecting plant traits, modifying root exudation, recruiting resident microbial functions, introducing compatible inoculants and managing the soil environment. This critical narrative review evaluates the mechanistic and translational evidence for these approaches in soils affected by potentially toxic elements, petroleum hydrocarbons and other persistent organic contaminants. Peer-reviewed experimental studies, field investigations and relevant syntheses were considered, with emphasis on causal attribution, pollutant fate, biological function and the durability of remediation outcomes. Root exudates alter nutrient supply, microbial substrate preferences, sorption and contaminant speciation, but their effects are conditional on concentration, plant development and soil chemistry. Bacteria and fungi can improve plant establishment, catalyse organic contaminant transformation or alter metal mobility; the same intervention can therefore favour phytoextraction in one context and immobilisation in another. Experimental evidence is persuasive for selected plant-microbe combinations and short-term mesocosms, whereas evidence for persistent field-scale enhancement remains less uniform. Contrasting hydrocarbon studies demonstrate that enriched degrader genes and changed microbiomes do not necessarily translate into greater net removal relative to unplanted controls. Mixtures of metals and organics create additional trade-offs between contaminant availability, plant stress and off-site transfer. The review proposes an outcome-led approach in which engineering choices are linked to a specified remediation mechanism, site-specific soil constraints and independently measured end points. Priority research needs include longitudinal field comparisons, flux-based pollutant accounting, direct tests of microbial activity and colonisation, and monitoring of leaching, food-chain exposure and contaminated biomass. Rhizosphere engineering is best treated as a controllable ecological intervention whose value must be established by improved risk-relevant outcomes rather than by microbiome change alone.

Heavy Metal Stress and Plant Adaptation in Contaminated Environments: Physiological, Biochemical and Molecular Mechanisms of Tolerance, Detoxification and Hyperaccumulation

Shweta Nag — 2026-11-13

Metal and metalloid contamination exposes plants to chemically diverse stressors whose consequences depend on soil speciation, exposure history, genotype and tissue-level transport. This critical narrative review examines how plants avoid, tolerate, detoxify or exceptionally hyperaccumulate potentially toxic elements, with particular attention to cadmium, arsenic, zinc, nickel, lead and copper. Literature available up to 1 September 2026 was evaluated through accessible scholarly records and original studies, alongside mechanistic reviews and field-oriented research. Evidence is strongest for the involvement of membrane transporters in element uptake and partitioning, glutathione-derived phytochelatins and associated vacuolar transport in cytosolic detoxification, and constitutive transporter regulation in certain hyperaccumulators. Physiological stress responses encompass altered root development, mineral nutrition, photosynthesis and redox regulation, but the frequent use of very high soluble metal doses complicates extrapolation to contaminated soils. Furthermore, increased antioxidant activity or transcript abundance does not independently demonstrate tolerance. Experimental genetics in rice and Arabidopsis establishes several causal transporter functions, while field-validated crop safety outcomes and long-term remediation performance remain less generalisable. Hyperaccumulation must be distinguished from root retention and from survival at high external concentrations; claimed metal removal is also constrained by harvestable biomass, soil resupply and management of contaminated residues. A unifying interpretation is proposed in which exposure chemistry, entry control, intracellular buffering, allocation and fitness determine whether a phenotype represents acclimation, inherited tolerance or useful phytoextraction. Priority studies should combine realistic multi-element soils, isotope-resolved fluxes, spatially resolved chemical measurements, causal molecular perturbation and multi-season field endpoints. The practical aim is not maximal metal tolerance in every context but appropriate partitioning: safe edible tissues in crops, immobilisation for stabilisation and recoverable shoot accumulation in dedicated non-food systems.