Enhancing copper and arsenic phytoextraction from calcareous soil through the synergistic interaction of ethylenediaminetetraacetic acid application timing and metal-resistant plant growth-promoting rhizobacteria inoculation.
Aug 2026· International journal of phytoremediation· pp.
1-16
· 0 citations· 55 references
Medicine
Abstract
Remediating calcareous soils co-contaminated with copper and arsenic remains a major challenge due to low metal bioavailability and the risk of chelator-induced phytotoxicity, which can severely limit phytoremediation success. This study investigated a synergistic strategy combining heavy metal-resistant plant growth-promoting rhizobacteria (PGPR) with precisely timed ethylenediaminetetraacetic acid (EDTA) application to improve phytoextraction efficiency in corn (Zea mays). Eight PGPR isolates were obtained from contaminated soil, and three strains (Stenotrophomonas sp. A22, Pseudomonas sp. A2 and A5) were selected based on their high resistance to Cu (up to 400 mg L-1) and As (up to 250 mg L-1), as well as multiple plant growth-promoting traits. In a controlled pot experiment, we evaluated bacterial inoculation and EDTA application at 20, 35, or 45 days after planting on plant growth, physiological performance, and metal uptake. Early EDTA addition (day 20) caused severe phytotoxicity, markedly reducing root and shoot biomass and depressing photosynthetic efficiency (Fv/Fm). In contrast, delaying EDTA application to days 35 or 45 substantially alleviated these adverse effects. PGPR inoculation, particularly with strain A5, further mitigated EDTA-induced stress and improved biomass production and physiological status. The combined PGPR-EDTA treatments significantly increased soil metal bioavailability and enhanced plant uptake, with maximum shoot Cu (214 mg kg-1) and As (99 mg kg-1) concentrations observed with strains A5 or A2 and EDTA application at day 20. Sequential extraction confirmed that these PGPR-EDTA treatments shifted metals from residual and oxide-bound pools into more soluble and exchangeable/carbonate-bound fractions. The findings support a mechanistically informed, optimized phytoremediation strategy for calcareous soils, based on the optimal timing of EDTA application and inoculation with metal-resistant PGPR.
Cadmium (Cd) accumulation in plants poses a serious risk to crop growth and human health. Although rhizobacteria are known to enhance plant Cd tolerance, research on rhizobacterial consortium to alleviate Cd toxicity in crops under hydroponic conditions remains limited. Two rhizobacterial strains, Bacillus cereus TLMC1 and Pseudomonas putida TLMC5, exhibiting high Cd tolerance and strong plant growth-promoting (PGP) traits, were selected to investigate their synergistic effects on Artemisia selengensis Turcz under Cd stress. Single and co-inoculation significantly decreased shoot Cd content and increased root Cd content, with co-inoculation yielding the lowest Cd translocation factors (0.08 and 0.09 under 1 and 10 mg L-1 Cd stress, respectively). Co-inoculation maximally reduced SOD and POD activities by 27.52% and 20.34% under 1 mg L-1 Cd stress. Soluble sugars, soluble proteins, vitamin C, and total flavonoids in edible shoots were all elevated, with co-inoculation showing optimal performance. Despite the reduction of Target Hazard Quotient (THQ) after inoculation, the minimum value remained above the safety threshold. These findings demonstrated that TLMC1 and TLMC5 co-inoculation effectively reduced Cd uptake and enriched nutritional and active components in the edible parts of A. selengensis, offering a preliminary microbial strategy for Cd risk mitigation in moderately Cd-polluted regions.
Mi Shen, Wei Kang, Ruofei Liu et al.· International journal of phy...· 0 citations
This study evaluated the potential of Protaetia brevitarsis frass as an organic amendment for the safe cultivation of Scutellaria baicalensis in Cr-As-contaminated soil. A greenhouse pot experiment was conducted with five frass application gradients (CK, LD, MD, HD, and VHD) to assess rhizosphere properties, plant growth, and metal accumulation risk. Frass application improved soil water status, nutrient supply, and microbial biomass, but VHD markedly increased electrical conductivity, indicating a potential salinity risk. Plant growth showed a dose-dependent tradeoff: HD favored root development and leaf physiological activity, whereas VHD promoted shoot growth but reduced root allocation. The frass was rich in alkali-hydrolyzable nitrogen and available phosphorus, suggesting that soil N and P increases resulted from both direct nutrient input and rhizosphere transformation. Frass treatments generally reduced Cr and As accumulation in S. baicalensis, although responses varied between metals and application rates. Redundancy analysis identified alkali-hydrolyzable nitrogen as the major explanatory factor (82.6%). Because metal fractions were not determined, BCF was interpreted as an uptake-risk indicator rather than direct evidence of soil passivation. HD is recommended under the present pot conditions.
Zhenxiang Xia, Yanru Zhang, Xiu-Hua Wu et al.· International journal of phy...· 0 citations
Citric acid (CA) and nitrogen (N) fertilizers have been widely applied to enhance phytoremediation of various contaminated soils, yet their combined effects and underlying mechanisms in cadmium (Cd)–polycyclic aromatic hydrocarbon (PAH) co-contaminated systems remain poorly understood. Here, we investigated the combined effects of CA and ammonium nitrate on the phytoremediation of Cd–phenanthrene (Phe) co-contaminated soil using marigold (Tagetes patula L.), with random forest, mantel tests, and structural equation modeling employed to explore hypothesized pathways and associations. The results demonstrated that combined CA and N application significantly promoted plant growth, Cd uptake, and Phe dissipation. Among the tested treatments, the low-dose combination (1 g CA + 0.1 g N pot−1) increased plant biomass by 88%, enhanced shoot Cd uptake by 121%, and achieved a Phe dissipation rate of 76.56%, representing the optimal remediation strategy. Mechanistically, the synergy between CA and N extends beyond simple growth promotion—N drives biomass production and, independently, facilitates Cd mobilization through rhizosphere acidification, while CA enhances contaminant bioavailability and buffers N-induced salt stress, together maintaining rhizosphere ionic homeostasis for efficient Cd translocation and Phe dissipation. This study provides a mechanistic framework for designing combined amendment strategies to enhance phytoremediation of co-contaminated soils.
The integrated application of nZVI particles and a microbial consortium was very effective in improving plant growth, mitigating Cd-accumulation in plants, confirming Cd-immobilization, and removing PHCs from soil, highlighting the potential of nano-enhanced bioremediation as a sustainable solution for the treatment and management of soil co-contaminated with inorganic and organic pollutants.
Visha Habib, Muhammad Imran Khan, Qammar Farooq et al.· BMC Plant Biology· 0 citations
Euryale ferox Salisb. is an ecologically and economically important aquatic macrophyte widely cultivated in the wetlands of North Bihar, India, where increasing metal contamination may pose risks to plant growth and wetland sustainability. The present study evaluated the comparative phytotoxicity, growth responses, tissue-specific metal accumulation, and phytoremediation potential of E. ferox exposed to chromium (Cr), lead (Pb), and cadmium (Cd). Plants were subjected to 0, 50, 100, 150, 200 and 250 μM concentrations of the respective metals under controlled conditions. Morphological and growth responses were assessed together with visual toxicity symptoms, biomass production, metal accumulation in roots and shoots, bioaccumulation factor (BAF), and translocation factor (TF). All three metals produced concentration-dependent reductions in plant height, leaf number, leaf area, root length, fresh biomass and dry biomass. The inhibitory effects were most pronounced under Cd exposure, followed by Cr and Pb. At 250 μM, Cd reduced plant height, leaf area, root length, fresh biomass and dry biomass by approximately 31.3%, 42.2%, 40.2%, 34.2% and 38.7%, respectively, relative to the control. Visual toxicity also increased progressively with metal concentration, with overall stress indices reaching 19, 18 and 15 under Cd, Cr and Pb, respectively. Metal accumulation was predominantly localised in roots, with Pb showing the highest accumulation, reaching 1495 ± 38 mg kg⁻¹ dry weight at 250 μM. BAF values were highest for Pb (12.3–14.8), while TF remained below 1 for all metals, indicating restricted translocation to shoots. In addition, E. ferox substantially reduced dissolved metal concentrations in the growth medium, with reported removal of 41–73% Cr, 46–78% Pb and 38–70% Cd after seven days. These findings demonstrate that E. ferox exhibits considerable metal tolerance together with strong root-based metal sequestration. Although its low TF excludes it as an efficient phytoextractor, its pronounced root accumulation and metal-removal capacity indicate promising applications in rhizofiltration and phytostabilisation of multi-metal-contaminated aquatic habitats.
Asifa Naseeb, Avinash Kumar, Manisha Kumari et al.· Journal of Advances in Biolo...· 0 citations
Introduction Phytoremediation using fast-growing tree species has emerged as a sustainable approach for restoring metal-contaminated soils. However, comparative information on species-specific responses to metal stress tolerance remains limited. Methods This study evaluated chlorophyll content, growth performance, and biomass allocation, including metal tolerance efficiency, of four Eucalyptus species (i.e., E. tereticornis, E. camaldulensis, E. globulus, and E. citriodora) under varying concentrations of Cadmium (Cd, 25, 50, and 100 mg kg⁻¹) and Lead (Pb, 100, 125, and 250 mg kg⁻¹). A factorial, completely randomized pot experiment was conducted under controlled conditions, using sterilized red soil as the medium for 120 days. Plant growth performance and metal tolerance efficiency were measured and analyzed using ANOVA followed by post hoc comparison. Results Cd exhibited significantly greater phytotoxicity than Pb across species and parameters studied. Marked species-specific differences in metal tolerance were observed in Eucalyptus citriodora, outperforming other species in maintaining superior growth performance and metal tolerance even at the highest metal concentrations (Cd 100 mg kg⁻¹). However, E. camaldulensis was the species most sensitive to Cd stress. Hierarchical clustering rank based on superior tolerance characteristics of species was: E. citriodora > E. camaldulensis > E. tereticornis > E. globulus. Discussion It was concluded that Eucalyptus citriodora was the most promising candidate for future phytoremediation studies of Cd- and Pb-contaminated soils due to its superior metal tolerance ability as reflected by sustained growth performance and chlorophyll retention of the species. The species can be recommended for restoration programs and sustainable management of metal-polluted areas based on performance at the initial phase.
G. Patil, Muthusamy Palani Divya, Abhishek Maitry et al.· Frontiers in Plant Science· 0 citations
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