Effect of farmyard manure, elemental sulphur and EDTA on growth and phytoextraction of cadmium by spider plants (Chlorophytum comosum L.) under Cd stress

Integration of comparative cytology, ionome, transcriptome and metabolome provide a basic framework for the response of foxtail millet to Cd stress

Apart from directly affecting the growth and development of crops, Cd in the soil can easily enter the human body through the food chain and pose a threat to human health. Therefore, understanding the toxicity of Cd to specific crops and the molecular mechanisms of their response to Cd is essential. In this study, hydroponic experiments were utilized to study the response of foxtail millet to Cd stress through phenotypic investigation, enzyme activity determination, ultrastructure, ionome, transcriptome and metabolome. With the increase in cadmium concentration, both the growth and photosynthetic capacity of foxtail millet seedlings are severely inhibited. The ultrastructure of cells is damaged, cells are deformed, chloroplasts swell and disappear, and cell walls thicken. Cd stress affects the absorption, transport, and redistribution of beneficial metal ions in the seedlings. Multi-omics analysis reveals the crucial roles of glycolysis, glutathione metabolism and phenylpropanoid and lignin biosynthesis pathways in Cd detoxification via energy metabolism, the antioxidant system and cell wall changes. Finally, a schematic diagram of foxtail millet in response to Cd stress was we preliminarily drew. This work provides a basic framework for further revealing the molecular mechanism of Cd tolerance in foxtail millet.

Phytostabilization potential and microbial response to the reclamation of native Cynodon dactylon in spoil heaps from a multiple-metal mining site in Southwest China

Phytocapping offers a sustainable approach for managing exposed tailings by mitigating pollutant spread and enhancing phytoremediation. This study investigates the potential of Bermudagrass (Cynodon dactylon) as a pioneering plant for rehabilitating tailings from an open-pit lead-zinc mine in Southwest China. Our findings demonstrate that Bermudagrass significantly improved soil quality and multifunctionality compared to adjacent bare tailings. Soil improvements included increases in organic matter (107%), total and available nitrogen (50% and 110%, respectively), available phosphorus (170%), and soil enzyme activities, including β-glucosidase (170%), sucrase (1729%), alkaline phosphatase (3722%), and acid phosphatase (168%). The reclamation process also promoted microbial community succession, altering community composition, improving microbial diversity, and enhancing bacterial biomass from (0.89 ± 0.54) × 1015 to (9.06 ± 3.25) × 1015 copies/g in rhizosphere soils. Greenhouse experiments further confirmed Bermudagrass's resilience to cadmium (Cd), with both mining and non-mining ecotypes thriving in tailing soils and Cd2+ hydroponic solutions (up to 44.5 μM) without evident phytotoxicity. Bermudagrass roots exhibited exceptional Cd accumulation (bioconcentration factor: 181-1006) while minimizing Cd translocation to shoots (translocation factor: <0.13). Inoculation with Funneliformis mosseae, a restored root-mutually symbiotic fungus, further mitigated Cd-induced phytotoxicity and enhanced plant growth. These findings highlight Bermudagrass as a promising pioneer species for phytostabilization in severely contaminated mining environments, with its rhizosphere microbiome playing a critical role in facilitating ecosystem restoration. Sustainable plant establishment in mine waste rock requires concurrent development of belowground fertility and healthy rhizospheric soil. Ultimately, successful revegetation depends on integrated above and belowground development to achieve long-term ecological restoration.

Application of synthesized metal-trimesic acid frameworks for the remediation of a multi-metal polluted soil and investigation of quinoa responses

Metal-organic frameworks (MOFs) are structures with high surface area that can be used to remove heavy metals (HMs) efficiently from the environment. The effect of MOFs on HMs removal from contaminated soils has not been already investigated. Monometallic MOFs are easier to synthesize with high efficiency, and it is also important to compare their structures. In the present study, Zn-BTC, Cu-BTC, and Fe-BTC as three metal-trimesic acid MOFs were synthesized from the combination of zinc (Zn), copper (Cu), and iron (Fe) nitrates with benzene-1,3,5-tricarboxylic acid (H3BTC) by solvothermal method. BET analysis showed that the specific surface areas of the Zn-BTC, Cu-BTC, and Fe-BTC were 502.63, 768.39 and 92.4 m2g-1, respectively. The synthesized MOFs were added at the rates of 0.5 and 1% by weight to the soils contaminated with 100 mgkg-1 of Zn, nickel (Ni), lead (Pb), and cadmium (Cd). Then quinoa seeds were sown in the treated soils. According to the results, the uptakes of all four HMs by quinoa were the lowest in the Cu-BTC 1% treated pots and the lowest uptakes were observed for Pb in shoot and root (4.87 and 0.39, μgpot-1, respectively). The lowest concentration of metal extracted with EDTA in the post-harvest soils was for Pb (11.86 mgkg-1) in the Cu-BTC 1% treatment. The lowest metal pollution indices were observed after the application of Cu-BTC 1%, which were 20.29 and 11.53 for shoot and root, respectively. With equal molar ratios, highly porous and honeycomb-shaped structure, the most crystallized and the smallest constituent particle size (34.64 nm) were obtained only from the combination of Cu ions with H3BTC. The lowest porosity, crystallinity, and a semi-gel like feature was found for the Fe-BTC. The synthesized Cu-BTC showed the highest capacity of stabilizing HMs, especially Pb in the soil compared to the Zn-BTC and the Fe-BTC. The highly porous characteristic of the Cu-BTC can make the application of this MOF as a suitable environmental solution for the remediation of high Pb-contaminated soils.

Bioassessment of Cd and Pb at Multiple Growth Stages of Wheat Grown in Texturally Different Soils Using Diffusive Gradients in Thin Films and Traditional Extractants: A Comparative Study

The bioavailability of heavy metals in soil is a crucial factor in determining their potential uptake by plants and their subsequent entry into the food chain. Various methods, including traditional chemical extractants and the diffusive gradients in thin films (DGT) technique, are employed to assess this bioavailability. The bioavailability of heavy metals, particularly cadmium (Cd) and lead (Pb), is also influenced by soil texture and their concentrations in the soil solution. The primary objectives of this experiment were to compare and correlate the assessment of the Cd and Pb bioavailability using the DGT technique and traditional extractants across two soil textural classes: sandy clay loam (SCL) and clay loam (CL) at two contamination levels: aged contaminated (NC) and artificially contaminated (AC). The specific objectives included assessing the bioavailability of Cd and Pb at different growth stages of the wheat plant and correlating the DGT-based bioassessments of Cd and Pb with their concentrations in various plant parts at different growth stages. This study also compared the effectiveness of the DGT method and traditional extraction techniques in assessing the bioavailable fractions of Cd and Pb in soil. The regression analysis demonstrated strong positive correlations between the DGT method and various extraction methods. The results showed that the wheat plants grown in the AC soils exhibited lower root, shoot, and grain weights compared to those grown in the NC soils, indicating that metal contamination negatively impacts plant performance. The concentrations of Cd and Pb in the wheat tissues varied across different growth stages, with the highest levels observed during the grain filling (S3) and maturity (S4) stages. It is concluded that the in situ assessment of Cd and Pb though DGT was strongly and positively correlated with the Cd and Pb concentration in wheat plant parts at the maturity stage. A correlation and regression analysis of the DGT assessment and traditional extractants showed that the DGT method provides a reliable tool for assessing the bioavailability of Cd and Pb in soils and helped in developing sustainable soil management strategies to ensure the safety of agricultural products for human consumption.

Effects of N, N-bis (carboxymethyl)-L-glutamic acid and polyaspartic acid on the phytoremediation of cadmium in contaminated soil at the presence of pyrene: Biochemical properties and transcriptome analysis

Chelator-assisted phytoremediation is an efficacious method for promoting the removal efficiency of heavy metals (HMs). The effects of N, N-bis(carboxymethyl)-L-glutamic acid (GLDA) and polyaspartic acid (PASP) on Cd uptake and pyrene removal by Solanum nigrum L. (S. nigrum) were compared in this study. Using GLDA or PASP, the removal efficiency of pyrene was over 98%. And PASP observably raised the accumulation and transport of Cd by S. nigrum compared with GLDA. Meanwhile, both GLDA and PASP markedly increased soil dehydrogenase activities (DHA) and microbial activities. DHA and microbial activities in the PASP treatment group were 1.05 and 1.06 folds of those in the GLDA treatment group, respectively. Transcriptome analysis revealed that 1206 and 1684 differentially expressed genes (DEGs) were recognized in the GLDA treatment group and PASP treatment group, respectively. Most of the DEGs found in the PASP treatment group were involved in the metabolism of carbohydrates, the biosynthesis of brassinosteroid and flavonoid, and they were up-regulated. The DEGs related to Cd transport were screened, and ABCG3, ABCC4, ABCG9 and Nramp5 were found to be relevant with the reduction of Cd stress in S. nigrum by PASP. Furthermore, with PASP treated, transcription factors (TFs) related to HMs such as WRKY, bHLH, AP2/ERF, MYB were down-regulated, while more MYB and bZIP TFs were up-regulated. These TFs associated with plant stress resistance would work together to induce oxidative stress. The above results indicated that PASP was more conducive for phytoremediation of Cd-pyrene co-contaminated soil than GLDA.

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.

Revitalizing contaminated lands: A state-of-the-art review on the remediation of mine-tailings using phytoremediation and genomic approaches

The mining industry has historically served as a critical reservoir of essential raw materials driving global economic progress. Nevertheless, the consequential by-product known as mine tailings has consistently produced a substantial footprint of environmental contamination. With annual discharges of mine tailings surpassing 10 billion tons globally, the need for effective remediation strategies is more pressing than ever as traditional physical and chemical remediation techniques are hindered by their high costs and limited efficacy. Phytoremediation utilizing plants for remediation of polluted soil has developed as a promising and eco-friendly approach to addressing mine tailings contamination. Furthermore, sequencing of genomic DNA and transcribed RNA extracted from mine tailings presents a pivotal opportunity to provide critical supporting insights for activities directed towards the reconstruction of ecosystem functions on contaminated lands. This review explores the growing prominence of phytoremediation and metagenomics as an ecologically sustainable techniques for rehabilitating mine-tailings. The present study envisages that plant species such as Solidago chilensis, Festuca arundinacea, Lolium perenne, Polygonum capitatum, Pennisetum purpureum, Maireana brevifolia, Prosopis tamarugo etc. could be utilized for the remediation of mine-tailings. Furthermore, a critical evaluation of the organic and inorganic ammendments that optimize conditions for the remediation of mine tailings is also provided. The focus of this review extends to the exploration of environmental genomics to characterize microbial communities in mining sites. By delving into the multifaceted dimensions of phytoremediation and genomics for mine tailings, this study contributes to the ongoing efforts to revitalize contaminated lands for a sustainable and environmentally friendly future.