Search Results (1,167)

Heavy metal pollution is one of the most devastating abiotic factors, significantly damaging crops and human health. One of the serious problems it causes is a rise in cadmium (Cd) toxicity. Cd is a highly toxic metal with a negative biological role, and it enters plants via the soil–plant system. Cd stress induces a series of disorders in plants’ morphological, physiological, and biochemical processes and initiates the inhibition of seed germination, ultimately resulting in reduced growth. Fiber crops such as kenaf, jute, hemp, cotton, and flax have high industrial importance and often face the issue of Cd toxicity. Various techniques have been introduced to counter the rising threats of Cd toxicity, including reducing Cd content in the soil, mitigating the effects of Cd stress, and genetic improvements in plant tolerance against this stress. For decades, plant breeders have been trying to develop Cd-tolerant fiber crops through the identification and transformation of novel genes. Still, the complex mechanism of Cd tolerance has hindered the progress of genetic breeding. These crops are ideal candidates for the phytoremediation of heavy metals in contaminated soils. Hence, increased Cd uptake, accumulation, and translocation in below-ground parts (roots) and above-ground parts (shoots, leaves, and stems) can help clean agricultural lands for safe use for food crops. Earlier studies indicated that reducing Cd uptake, detoxification, reducing the effects of Cd stress, and developing plant tolerance to these stresses through the identification of novel genes are fruitful approaches. This review aims to highlight the role of some conventional and molecular techniques in reducing the threats of Cd stress in some key fiber crops. Molecular techniques mainly involve QTL mapping and GWAS. However, more focus has been given to the use of transcriptome and TFs analysis to explore the potential genomic regions involved in Cd tolerance in these crops. This review will serve as a source of valuable genetic information on key fiber crops, allowing for further in-depth analyses of Cd tolerance to identify the critical genes for molecular breeding, like genetic engineering and CRISPR/Cas9. Full article

This paper provides an overview of the impacts of mining-related environmental liabilities on humans, soils, sediments, surface water and groundwater across various mining districts in Zacatecas, Mexico. An analysis has been carried out on the areas of the state most affected by the presence of potentially toxic elements (PTEs) such as arsenic, lead, cadmium, copper, chromium and zinc, identifying priority areas for environmental assessment and remediation. Likewise, a review of the concentrations of PTEs reported in different environmental matrices of the state’s mining areas with the presence of environmental liabilities was carried out, most of which exceed the maximum permissible limits established by Mexican and international regulations, generating an environmental risk for the populations near these districts due to their potential incorporation into the food chain. Additionally, this study explores research focused on the biostabilization of PTEs using microorganisms with specific metabolic activities. Phytoremediation is presented as a viable tool for the stabilization and elimination of PTEs, in which endemic plants from arid–semi-arid climates have shown favorable results in terms of the phytostabilization and phytoextraction processes of the PTEs present in mining waste. Full article

Submerged aquatic plants have potential applications in the phytoremediation of aquatic environments contaminated with arsenic (As). However, the role of epiphytic bacteria that grow on the surface of plants in As uptake and metabolism in plants has often been overlooked. An orthogonal experimental design with nine treatments, four factors, and three levels was conducted to inspect the effects of nitrogen (N, KNO₃, 2, 4, 10 mg/L), phosphorus (P, NaH₂PO₄·2H₂O, 0.02, 0.2, 1 mg/L), pH (6, 7, 9), and arsenate (As(V), Na₃AsO₄·12H₂O, 15, 75, 375 μg/L) on As accumulation and biotransformation in sterilized plants and to further explore the role of epiphytic bacteria in the metabolism of As by Hydrilla verticillata (L.f.) Royle. The results indicate that low N, intermediate P, and intermediate pH were beneficial for As accumulation (117.2 ± 62.2 μg/g DW) in sterilized plants, and epiphytic bacteria exhibited promotion (68%) in plants. High N promoted As absorption and transformation in non-sterilized plants but reduced As absorption in sterilized plants. Epiphytic bacteria in the medium showed significant As(III) oxidation, which was affected by environmental factors. These findings can promote remediation efficiency by regulating environmental factors for the phytoremediation of As-contaminated waters. Full article

Hyperaccumulators within the Noccaea genus possess many promising genetic and metabolic adaptations that could be potentially exploited to support phytoremediation efforts and/or crop improvement and biofortification. Although hyperaccumulation is very common in this genus, individual species display specific traits as they can accumulate different elements (e.g., zinc, cadmium, and/or nickel). Moreover, there appears to be some populational variability with natural selection increasing the metal tolerance in metallicolous populations. Therefore, employing robust methods, such as integrated analysis of the transcriptome and metabolome, is crucial for uncovering pivotal candidate genes and pathways orchestrating the response to metal stress in Noccaea hyperaccumulators. Our study highlights several species-specific traits linked to the detoxification of metals and metal-induced oxidative stress in hyperaccumulating N. praecox when compared to a closely related model species, N. caerulescens, when grown in the field. Transcriptome analysis revealed distinct differences between the three studied natural Noccaea populations. Notably, we observed several pathways frequently connected to metal stress, i.e., glutathione metabolism, phenylpropanoid biosynthesis, and flavonoid biosynthesis, which were enriched. These differences were observed despite the relative evolutionary closeness of studied species, which emphasizes the importance of further expanding our knowledge on hyperaccumulators if we want to exploit their mechanisms for phytoremediation efforts or food quality improvements. Full article

Soil contamination by cadmium (Cd), lead (Pb), and zinc (Zn) at the Tar Creek superfund site in northeast Oklahoma, United States, remains a threat to the environment and local ecosystem. Phytoremediation with industrial hemp (Cannabis sativa L.) and the use of biochar (BC) have been independently shown to be effective methods to remediate heavy-metal-contaminated soils. The objective of this greenhouse study was to evaluate the effects of industrial hemp cultivar (‘Carmagnola’ and ‘Jinma’), biochar rate (0, 2, 5, and 10% by volume), soil contamination level (low, medium, and high), and their interactions on above- (AG) and belowground dry matter (DM) and AG tissue concentrations, as well as uptakes of Cd, Pb, and Zn after 90 days of growth in naturally contaminated soils from the Tar Creek superfund site. Aboveground DM was the largest (p < 0.01) in the low- (0.06 g cm⁻²) and smallest in the high-contaminated soil (0.03 g cm⁻²), and was unaffected (p > 0.05) by cultivar or BC rate. Averaged across BC rates, AG tissue Pb and Zn concentrations from the high-’Carmagnola’ and -’Jinma’ combinations were at least 2.4 times greater than from the other four soil–cultivar combinations. Averaged across cultivars, AG tissue Pb uptake in the high-5 and high-10% BC combinations were at least 2.7 times greater than in the high-0 and high-5% BC combinations, which did not differ. The results indicated that both ‘Carmagnola’ and ‘Jinma’ may be suitable choices for phytoremediation of mixed Cd-, Pb-, and Zn-contaminated soil when grown in combination with 5 or 10% (v/v) BC. Full article

The Alyssum genus, with its many metal-adapted species, is a good candidate for research on phytoremediation and metal tolerance mechanisms. These goals can be supported by elaborating on an in vitro multiplication protocol. Our study aimed to determine the aseptic conditions for the growth and effective propagation of Alyssum murale, A. alyssoides, and A. montanum, each exhibiting different adaptation strategies to nickel ions. Firstly, hydrogen peroxide (H₂O₂) or sodium nitroprusside (SNP) were investigated in the biological Lepidium test to find their optimal concentrations that could improve the germination attributes of tested Alyssum species. The concentration of 0.5 mM H₂O₂ or SNP was selected for research on Alyssum seeds, which were the initial material to start in vitro cultivation. Regardless of the species, H₂O₂ harmed germination percentage; however, its application accelerated radicle emergence, especially in metal-sensitive genotypes, while in both metal-tolerant ones, the germination time of H₂O₂-treated seeds was similar to that of treated with SNP. These findings provide a novel insight into the effect of H₂O₂ or SNP on seeds, contributing to a better understanding of their role in the germination of different genotypes. Among tested media compositions, the synchronous plant regeneration of all species was achieved on MS medium supplemented with 0.5 mg/L 2iP and 0.1 mg/L IAA, making an essential advancement in the in vitro protocols for metallophytes. Full article

Chromium is an essential element in various industrial processes, including stainless steel production, electroplating, metal finishing, leather tanning, photography, and textile manufacturing. However, it is also a well-documented contaminant of aquatic systems and agricultural land, posing significant economic and health challenges. The hexavalent form of chromium [Cr(VI)] is particularly toxic and carcinogenic, linked to severe health issues such as cancer, kidney disorders, liver failure, and environmental biomagnification. Due to the high risks associated with chromium contamination in potable water, researchers have focused on developing effective removal strategies. Among these strategies, biosorption has emerged as a promising, cost-effective, and energy-efficient method for eliminating toxic metals, especially chromium. This process utilizes agricultural waste, plants, algae, bacteria, fungi, and other biomass as adsorbents, demonstrating substantial potential for the remediation of heavy metals from contaminated environments at minimal cost. This review paper provides a comprehensive analysis of various strategies, materials, and mechanisms involved in the bioremediation of chromium, along with their commercial viability. It also highlights the advantages of biosorption over traditional chemical and physical methods, offering a thorough understanding of its applications and effectiveness. Full article

Mercury is classified as one of the world’s most toxic and dangerous pollutants as it tends to bioaccumulate and biomagnify within the trophic chain and is persistent. Various approaches are available to remediate Hg-affected sites including phytoremediation, which includes the use of plants to clean up contaminated environments. The phytoremediation of mercury contamination is attracting increasing attention because of its advantages: it is environmentally friendly, inexpensive, simple, and can improve soil fertility. In this report, VOSviewer (version 1.6.1) and Bibliometrix (version 4.16) software were used to analyze 457 and 697 documents published from 2000 to 2023, retrieved from the databases WoS and Scopus, respectively. China, India, the United States, and Spain were the top four most productive countries. The largest topic area was environmental sciences, and the Chinese Academy of Sciences was the organization that contributed the most to the overall number of publications. The keywords with the highest frequency excluding phytoremediation and mercury in WoS were heavy metals, accumulation, cadmium, soils, and phytoextraction. In Scopus, the most frequent keywords were bioremediation, heavy metals, soil pollution, bioaccumulation, biodegradation, and environmental. From the above analysis, we concluded that future research should focus on (1) finding native plants, (2) genetic engineering applications, (3) increasing remediation ability through assisted phytoremediation, and (4) the detoxification mechanism of mercury. This study provides insights into trending themes and serves as a reference for future research. Full article

Natural water resources often contain fluorides and chlorides due to wastewater discharge; however, excessive exposure to fluorides can pose health risks to humans. Elevated chloride levels can negatively affect aquatic fauna and disrupt the reproductive rates of plants. This study assessed constructed wetlands (CWs) featuring monocultures (including Canna hybrid, Alpinia purpurata, and Hedychium coronarium) and polycultures (combinations of species from the monoculture systems) of ornamental plants (OPs) to evaluate their efficiency in removing fluorides and chlorides. The results revealed that the ornamental plants flourished in the CW conditions without sustaining any physical damage. C. hybrid demonstrated the longest roots and the highest volume, as well as greater height compared to other species. However, this did not affect the ion removal efficiency. In polyculture systems, 42.2 ± 8.8% of fluoride was removed, a result that was not significantly different (p > 0.05) from the removal rates observed in monocultures of C. hybrid (42.5 ± 7.5%), H. coronarium (36.8 ± 7.0%), or A. purpurata (30.7 ± 7.9%). For chloride, a similar pattern emerged, with 32.4 ± 4.8% removed in constructed wetlands (CWs) using a polyculture of ornamental plants, a figure that was also not significantly different (p > 0.05) from the removal percentages in monocultures of C. hybrid (29.1 ± 5.3%), H. coronarium (28.1 ± 5.0%), or A. purpurata (32.0 ± 5.7%). Our results indicate that CWs with polyculture species contribute to pollutant removal at levels comparable to those found in monoculture systems. However, polyculture systems offer enhanced aesthetic appeal and biodiversity, incorporating various ornamental flowering plants. The use of this eco-technology for removing fluoride and chloride pollutants helps prevent river contamination and associated health issues. Full article

Four taxa of Spiraea were selected for this study: S. × cinerea Zabel ‘Grefsheim’, S. nipponica Maxim. ‘Snowmound’, S. splendens É. N. Baumann ex K. Koch and S. × vanhouttei (Briot) Carrière growing for a minimum of 5 years along heavily trafficked traffic routes. This study included the genus Spiraea due to its popularity in horticultural practice (commercial availability, widespread in urban environments). In addition, the use of ornamental shrubs for phytoremediation in urban green spaces effectively combines the aesthetic needs of residents with those of caring for the urban environment. This study was conducted in Poznań (population 550,000, the fifth largest city in Poland). Soils and foliage were examined in spring and autumn. Soil pH and specific electrolytic conductivity (EC) were determined. The content of micronutrients (Cu, Fe, Mn, Ni, Zn) and toxic heavy metals (Cd, Cr, Pb) in soil dry matter and leaves was determined. The uptake capacity of bioavailable forms of heavy metals by Spiraea from the soil was analyzed by determining the bioconcentration factor (BCF). It was found that the studied taxa meet the basic requirements for plants used for soil phytoremediation processes, especially for chromium phytoextraction. The degree of salinity of the tested soils did not pose a threat to the shrubs growing there, and most of the sites, despite the alkaline reaction, are suitable for their cultivation. S. × cinerea and S. × vanhouttei have BCFs for lead <1. The remaining taxa are characterized by strong concentrations of all analyzed elements. A particularly high BCF, above 10, was recorded for chromium and high for manganese and nickel. Full article

Acyl-CoA-binding protein (ACBP) genes have been implicated in lead enrichment and translocation in plants; however, the mechanisms by which these genes contribute to the response to heavy metal stress in various taxa have not been determined. In this study, the molecular mechanisms underlying the response of Robinia pseudoacacia, an economically important deciduous tree, to Pb stress were examined using transcriptomic and metabolomic analyses. RpACBP3 overexpression increased Pb enrichment, translocation, and tolerance. After Pb stress for 3 days, 1125 differentially expressed genes (DEGs) and 485 differentially accumulated metabolites (DAMs) were identified between wild-type and RpACBP3-overexpressing R. pseudoacacia strains; after Pb stress for 45 days, 1746 DEGs and 341 DAMs were identified. Joint omics analyses showed that the DEGs and DAMs were co-enriched in α-linoleic acid metabolism and flavonoid biosynthesis pathways. In particular, DEGs and DAMs involved in α-linoleic acid metabolism and flavonoid biosynthesis were up- and down-regulated, respectively. Moreover, RpACBP3 overexpression enhanced the ability to scavenge reactive oxygen species and repair cell membranes under stress by regulating LOX gene expression and increasing the phosphatidylcholine content, thereby improving the tolerance to Pb stress. These findings lay a theoretical foundation for the future application of RpACBP3 genes in plant germplasm resource creation and phytoremediation of Pb contaminated soil in which R. pseudoacacia grow. Full article

Phytoremediation of oil pollution using free-floating aquatic plants is a promising method for water body cleaning. In this study, the influence of Eichhornia crassipes and Pistia stratiotes on the degradation of oil pollution was investigated. The loss of oil alkanes and the rheological characteristics of water were evaluated, and an analysis of the emerging rhizospheric microbial communities was carried out using high-throughput sequencing. The presence of E. crassipes and P. stratiotes plants in oil-contaminated tanks had no effect on the degradation of oil alkanes. However, the presence of plants promoted the development of rhizospheric bacteria capable of growing in oil-contaminated environments. Alpha diversity of microbial communities in oil-contaminated samples was higher in the presence of plants. Additionally, plants significantly reduced the water/oil interfacial tension, which facilitated the availability of hydrocarbons for biodegradation. A difference was noted in the microbiome between E. crassipes and P. stratiotes. Changes in the composition of microbial communities highlight the potential of E. crassipes and P. stratiotes as rhizospheric hosts for microorganisms in the phytoremediation of water bodies. Full article

Currently, the problem of heavy metal pollution in China is becoming increasingly serious, which poses grave threats to the environment and human health. Owing to the non-biodegradability and toxicity of heavy metals, a more sustainable and ecological approach to remediate heavy metal pollution has always been a focus of attention for environmental researchers. In recent years, many scientists have found that phytoremediation aided by endophytes has high potential to remediate heavy metals owing to its low cost, effectiveness, environmental friendliness, and sustainability compared with physical and chemical methods. Indeed, the mechanism of interaction between endophytes, plants, and heavy metals in the soil is pivotal for plants to tolerate metal toxicity and thrive. In this review, we focus on the mechanism of how endophytic bacteria resist heavy metals, and the direct and indirect mechanisms employed by endophytic bacteria to promote the growth of plants and enhance phytoextraction and phytostabilization. Moreover, we also discuss the application of combinations of endophytic bacteria and plants that have been used to remediate heavy metal pollution. Finally, it is pointed out that although there have been many studies on phytoremediation systems that have been assisted by endophytes, large-scale field trials are important to deliver “real” results to evaluate and improve phytoremediation assisted with microorganisms in polluted natural environments. Full article

Background: Organic amendments are often used for the phytostabilization of heavy metal-contaminated soils. This study investigated the suitability of different municipal waste processing methods for phytostabilization. Methods: The two feedstocks, biowaste, and green waste, were tested without pretreatment after composting or after pyrolysis at different temperatures and atmosphere compositions. The suitability of the differently pretreated amendments for phytostabilization was tested on sewage farm soil contaminated with Cd, Cu, Ni, and Zn by measurement of maize growth, mineral content, and mobile heavy metal concentrations in the bulk and rhizosphere soil. Results: In contaminated soils, shoot and root growth increased markedly due to the soil amendments. Shoot concentrations of all four heavy metals were significantly higher in contaminated than non-contaminated soil, whereas Fe concentrations were lower in contaminated soil. The amendments increased shoot Cd concentrations and did not significantly affect the other elements. In contaminated soil, concentrations of heavy metals were generally lower in the rhizosphere than in the bulk soil. The soil amendments markedly lowered soil heavy metal concentrations, whereby the decrease was significantly influenced by feedstock and pretreatment. The differences in the amendments’ ability to reduce the soil mobile heavy metals were primarily, but not exclusively, determined by their effect on soil pH. Conclusion: The feedstock processing conditions significantly influenced the phytostabilization performance of green waste and biowaste. Optimal processing for phytostabilization depends on the heavy metal most important in the contamination of a specific site. Full article

In response to the current serious problem of soil cadmium (Cd) contamination in agricultural land, phytoremediation technology is a green and environmentally friendly application prospect; however, its remediation efficiency is currently limited. An enhanced phytoremediation technique was constructed using the biodegradable chelator aspartate diethoxysuccinic acid (AES) combined with the plant growth regulator gibberellic acid (GA₃) to enhance the formation of maize. This technique has been proven to have a superior remediation effect. However, the safety of the restoration technique is of particular importance. The remediation process not only removes the contaminants, but also ensures that the original structure and stability of the soil is not damaged. In this regard, the constructed enhanced phytoremediation technique was further investigated in this study using soil columns. In combination with microscopic tests, such as X-ray diffraction and scanning electron microscopy, this study investigated the effects of the remediation process on the distribution characteristics of Cd in soil aggregates, and the structure and stability of soil aggregates. This was conducted by analyzing, as follows: plant growth conditions; the morphology, structure and mineral composition of soil aggregates in different soil layers; and the changes in these characteristics. The results demonstrated that the enhanced phytoremediation technique constructed in this study has a negligible impact on the morphology and mineral composition of soil aggregates, while exerting a limited influence on soil structure stability. This indicates that the technique can facilitate the safe utilization of remediated contaminated soil. Full article