Search Results (195)

Heavy metal pollution due to mining activities poses a significant threat to agricultural production, ecosystem health, and food security in South Africa. This review integrates current knowledge on the use of mustard spinach (Brassica juncea (L.) Czern.) for the bioremediation of polluted water and soil, focusing on enhancing phytoremediation efficiency through the use of silicon-based biostimulant treatments. Mustard spinach is known for its capacity to accumulate and tolerate high levels of toxic metals, such as Pb, Cd, and Hg, owing to its strong physiological and biochemical defense mechanisms, including metal chelation, antioxidant activity, and osmotic adjustment. However, phytoremediation potential is often constrained by the negative impact of heavy metal stress on plant growth. Recent studies have shown that silicon-based biostimulants can alleviate metal toxicity by reducing metal bioavailability, increasing metal immobilization, and improving the antioxidative capacity and growth of plants. Combining silicon amendments with mustard spinach cultivation is a promising, eco-friendly approach to the remediation of mining-impacted soils and waters, potentially restoring agricultural productivity and reducing health risks to the resident populations. This review elucidates the multifaceted mechanisms by which silicon-enhanced phytoremediation operates, including soil chemistry modification, metal sequestration, antioxidant defense, and physiological resilience, while highlighting the practical, field-applicable benefits of this combined approach. Furthermore, it identifies urgent research priorities, such as field validation and the optimization of silicon application methods. Full article

Arsenic (As) and cadmium (Cd) in rice grains are major global food safety concerns. Iron (Fe) can help reduce both, but current Fe treatments suffer from poor stability, low leaf absorption, and fast soil immobilization, with unclear underlying mechanisms. To address these issues, an Fe-based metal–organic framework (MIL-88) was modified with sodium alginate (SA) to form MIL-88@SA. Its stability as a foliar inhibitor and its leaf absorption were tested, and its effects on As and Cd accumulation in rice were compared with those of soluble Fe (FeCl₃) and chelating Fe (HA + FeCl₃) in a field study on As–Cd co-contaminated rice paddies. Compared with the control, MIL-88@SA outperformed or matched the other Fe treatments. A single foliar spray during the tillering stage increased the rice yield by 19% and reduced the inorganic As and Cd content in the grains by 22.8% and 67.8%, respectively, while the other Fe treatments required two sprays. Its superior performance was attributed to better leaf affinity and thermal stability. Laser ablation inductively coupled plasma–mass spectrometry (LA–ICP–MS) and confocal laser scanning microscopy (CLSM) analyses revealed that Fe improved photosynthesis and alleviated As–Cd stress in leaves, MIL-88@SA promoted As and Cd redistribution, and Fe–Cd co-accumulation in leaf veins enhanced Cd retention in leaves. Full article

Heavy metal (HM) contamination poses a major threat to environmental health, agriculture and human well-being, requiring effective and sustainable remediation strategies. Phytoremediation, an eco-friendly and cost-effective approach, is widely used for the remediation of HM-contaminated soils. Although phytoremediation holds considerable potential in the extraction, stabilisation and degradation of HMs, its effectiveness is often constrained by limited metal bioavailability, plant stress under toxic conditions and slow metal uptake rates. To address these limitations, this review examines the integration of various soil amendments—the application of biochar, compost, plant exudates, microbial agents and chelating agents—to enhance phytoremediation efficiency. This review critically evaluates empirical evidence on the effectiveness, scalability, economic feasibility and environmental impact of these amendments. By synthesising recent studies, this review advances the understanding of amendment-assisted phytoremediation as a viable solution for treating HM-contaminated soils. In addition, this review identifies practical applications, discusses limitations and explores the potential synergies of these amendments to optimise phytoremediation strategies, ultimately contributing to more effective and sustainable environmental cleanup efforts. Full article

Cadmium (Cd) contamination in agricultural soils severely threatens rice production and food safety. To address this issue, this study developed transgenic rice lines co-expressing three Vitis vinifera genes: the ABCC transporter Vvmrp1 and metallothioneins Vvmt1 and Vvmt2. AlphaFold computational modeling confirmed the conserved ABCC-type transporter domain in VvMRP1. Under hydroponic conditions, transgenic rice showed remarkable Cd tolerance, surviving 30 mM Cd (lethal to wildtype, WT) without growth penalties, and exhibited 62.5% survival at 1 mM Cd vs. complete wild-type mortality. Field-relevant Cd exposure (1 mM) reduced Cd accumulation to 35.8% in roots, 83% in stems, and 76.8% in grains compared to WT. Mechanistic analyses revealed that Vvmrp1 mediates cellular Cd efflux while Vvmt1 and 2 chelate free Cd ions, synergistically inhibiting Cd translocation. Transgenic plants also maintained better Fe, P, and Mg homeostasis under Cd stress. This study pioneers the co-expression of a transporter with metallothioneins in rice, demonstrating their complementary roles in Cd detoxification without pleiotropic effects from endogenous gene modification. The findings provide an effective genetic strategy for cultivating low-Cd rice in contaminated soils, offering significant implications for food safety and sustainable agriculture. Full article

This research aimed to evaluate how different chemical forms of key nutrients, delivered through an advanced foliar product (PRO) and a standard formulation (TRA), influence maize performance when grown on contrasting soil types. Each fertilizer provided a set of macro- and micronutrients, including nitrogen, phosphorus, potassium, boron, copper, iron, manganese, molybdenum, and zinc, along with trace elements such as chromium, iodine, lithium, and selenium. In TRA, Fe and Zn were complexed with EDTA, and trace elements were present in mineral form. In PRO, Fe and Zn were chelated with amino acids, and trace elements were bound to plant extracts. The study examined increasing doses of PRO and their potential toxicity. Both fertilizers improved maize biomass: fresh weight increased by 5–8% and dry weight by 8–14%, depending on the dose. At the lowest dose, yields were similar. However, PRO was more effective in biofortifying maize with iron and zinc on sandy soil, increasing levels by 16% and 7% compared to TRA at the lowest dose and up to 29% at the highest dose. PRO was well tolerated at higher doses. No significant differences were observed between the second and third doses of PRO, suggesting reduced efficacy at the highest dose. Full article

Contamination of the soil with cadmium (Cd) presents serious hazards to plant growth, ecosystem harmony, and human health. Plants have evolved various mechanisms to address Cd toxicity, such as sequestration, chelation, and antioxidant defense systems. Knowledge of these mechanisms is an important requisite for the development of strategies to relieve Cd stress in plants. More recent studies also implicate the role of the neurotransmitter 5-hydroxytryptamine (serotonin) in enabling Cd mitigation behavior in plants. Beyond its well-known role in animals, serotonin has emerged as a vital signaling molecule in plants, contributing to stress responses and regulatory pathways. This review focuses on the different Cd tolerance mechanisms in plants and describes the role of serotonin in protection against Cd toxicity. Moreover, it investigates how serotonin interacts with other signaling molecules to coordinate Cd stress responses. Understanding the intricate network of Cd tolerance mechanisms and the involvement of serotonin is essential for developing effective strategies to combat Cd stress in plants and improve environmental quality. Full article

Rice, one of the global staple food crops, is significantly affected in its growth by cadmium (Cd) contamination in soil. This study comprehensively investigated the impact of Cd stress on the root exudates and rhizospheric soil microorganisms of rice through non-targeted metabolomics and high-throughput 16S rRNA sequencing technologies, as well as the ecological regulatory mechanisms between them. Root exudates reflect proactive plant defenses and enhance these capabilities by attracting beneficial microorganisms, which play a pivotal role in plant detoxification. There were significant changes in root exudates under Cd stress, their chelation and rejection of Cd ions diminished the bioavailability within the plant system, thereby mitigating the phytotoxic effects of heavy metal stress and safeguarding the overall health of plants. Moreover, Proteobacteria (Lysobacter, Pseudaminobacter, and Sphingomonas) were recruited by the root exudates from rice as potential participants in plant tolerance and detoxification processes. These findings offer novel insights into the ecological adaptability mechanisms of rice under heavy metal stress and provide potential biomarkers and microbial resources for agricultural environmental regulation. Full article

Cadmium (Cd) is an extremely toxic heavy metal that can move from the soil to plants and enter the human body via the food chain, causing severe health issues for humans. Phytoremediation uses hyperaccumulators to extract heavy metals from polluted soil. Phytohormones, wildly used plant growth regulators, have been explored to improve phytoremediation efficiency. Abscisic acid (ABA) is also an essential regulator of plant tolerance to biotic and abiotic stresses, including heavy metal-induced toxicity. Previous research has revealed that Phytolacca acinosa Roxb. (P. acinosa) has a strong ability to enrich Cd and can be used as a Cd hyperaccumulator. In this study, physiological and biochemical analysis revealed that under Cd stress, exogenous ABA application alleviated oxidative stress, increased the Cd²⁺ concentration in P. acinosa, especially in the roots, and changed the phytohormone concentration in P. acinosa. Transcriptome analysis was conducted to explore the molecular mechanisms by which ABA regulates Cd uptake and accumulation in P. acinosa, and to further understand the regulatory role of ABA. The results show that ABA treatment affected gene expression in P. acinosa roots under Cd stress. This study identified 5788 differentially expressed genes (DEGs) (2541 up-regulated and 3247 down-regulated). Moreover, 96 metal transport-related DEGs, 54 phytohormone-related DEGs, 89 cell wall-related DEGs, 113 metal chelation-related DEGs, and 102 defense system-related DEGs cooperated more closely under exogenous ABA application to regulate Cd uptake and accumulation in P. acinosa under Cd stress. These results may help to elucidate the mechanisms by which ABA regulates Cd uptake and accumulation in plants, and provide a reference for developing a phytohormone-based strengthening strategy to improve the phytoremediation ability of other hyperaccumulators or accumulator species. The key genes involved in ABA’s regulation of Cd uptake and accumulation in P. acinosa need to be further analyzed and functionally verified. This may expand our understanding of the molecular regulatory mechanisms underlying heavy metal uptake and accumulation in hyperaccumulators. Full article

Many of today’s innovative materials used to carry trace elements (TEs) are derived from chelates. Most of the materials used for this purpose have been produced on the basis of EDTA, which is not considered to be environmentally friendly due to its high persistence. Research is therefore being carried out to produce materials that do not pose an environmental risk. Therefore, a study was carried out to determine the effects of newly developed innovative materials with embedded biodegradable and environmentally safe chelates (IDHA—iminodisuccinic acid—and N-butyl-D-gluconamide ligands) containing copper, molybdenum and iron on the yield, biometric characteristics and chemical composition of soybean and selected soil properties. It is difficult to find publications on their effects in soybean cultivation. The greatest increase in soybean leaf greenness index (SPAD) was found after the addition of pure Salmag^® (Sal.^®). The effect of the chelates on the SPAD index was lower, with Sal.^® + Fe chelate having the greatest effect during the vegetative development stage and Cu chelate having the greatest effect during the flowering stage. Sal.^® + Cu, especially with Fe, accelerated pod and seed ripening in the last vegetative stage of soybean. Sal.^® + Cu had the most favourable impact on plant height, pure Sal.^® on the pod number per plant, Sal.^® + Fe on the seed number per pod, Sal.^® with Mo and Fe chelates on soybean seed yield, and pure Sal.^® on fresh weight remaining above-ground part yield, while pure Sal.^® and Sal.^® + Fe had the most favourable impact on dry weight aerial yield. The fertiliser materials (especially Sal.^® + Cu) generally increased the N content of the tested soybean organs and the Cu content of the other above-ground soybean parts (especially those containing chelates) and had an antagonistic effect on the Mg content of the soybean above-ground parts. Sal.^® + Cu also had a negative effect on the Fe content of other above-ground soybean parts. Sal.^® + Fe had a positive impact on the iron content, and Sal.^® + Mo had a positive impact on the molybdenum content of soybean. The applied fertilisers had little effect on the contents of Cu, Mo and Fe in the soil. There was only a significant increase in the Cu content of the soil after the addition of Sal.^® + Cu and a significantly smaller increase under the influence of Sal.^® without chelates, as well as an increase in the Mo content of the soil with Sal.^®. The present study confirms the beneficial impact of the novel materials with chelates. It has been demonstrated that the presence of materials containing Mo and, in particular, Cu has a considerable effect on the yield and quality characteristics of soybeans. Full article

Understanding soil properties that govern physicochemical and biological processes is essential for achieving high crop quality and yield. Organic matter is an important element of soil fertility and fertility in vegetable cultivation. In the process of decomposition of organic matter in the soil, humus of various quality is formed. The quality of humus depends on the content of individual acids (fulvic, humic and hymatomalanic acids) in it, which can affect the binding–chelation of heavy metals, limiting their availability to plants. The conducted studies determined the effect of adding organic matter (high peat, brown coal and wheat straw) to mineral soil on nickel detoxification in radish, its yield, nitrogen management and chloroplast pigments. The studies were conducted for three years in a greenhouse in a container system. The tested substrates were contaminated with nickel in the amount of 50, 75 and 100 mg dm⁻³. It was found that introducing organic matter into mineral soil can affect the reduction as well as the increase in nickel content in edible parts of radish. The type of organic material introduced into mineral soil as a source of organic matter has a significant impact on nickel content in radish. It was shown that nitrate reductase activity (NR) depends to a large extent on the substrate in which the plants are grown as well as on the applied dose of nickel. A similar relationship was demonstrated in the case of changes in the level of chloroplast pigments (chlorophyll a, chlorophyll b and carotenoids). Full article

Soil contamination with heavy metals (HMs) poses a significant environmental threat. Phytoremediation, a sustainable and eco-friendly emerging bioremediation approach, utilizes plants to remove, immobilize, or stabilize soil contaminants. This study examines the interactive effects of sulfur (S), ethylenediaminetetraacetic acid (EDTA), and olive mill wastewater (OMW) on HM uptake and the growth of maize (Zea mays L.) and mustard (Brassica juncea). Mustard exhibited superior dry matter (DM) yield (2.4 g/pot with 5% OMW), nutrient uptake, and tolerance to metal toxicity. The translocation factor (TF) and bioaccumulation factor (BF) for maize and mustard plants vary significantly with different treatments. For maize, the S 2T/ha treatment achieved the highest TF and BF for cadmium (Cd), while 5% OMW led to maximum chromium (Cr) and manganese (Mn) uptake. In mustard, 5% OMW treatment resulted in the greatest bioconcentration factor (BCF) for cadmium (Cd), lead (Pb), and zinc (Zn), whereas sulfur application yielded the highest TF for Cd. The 5% OMW treatment overall enhanced HM uptake most significantly. Lower sulfur application rate (1 ton/hectare) increased the availability Cd and Pb, boosting plant growth and nutrient uptake. For instance, 1 ton/hectare of sulfur elevated Cd availability to 24.102 mg·kg⁻¹ in maize and 58.705 mg·kg⁻¹ in mustard. EDTA treatments further improved metal bioavailability, increasing Cd levels in maize (10.09 mg·kg⁻¹) and mustard (7.78 mg·kg⁻¹). Mustard’s superior tolerance and nutrient efficiency identify it as a promising candidate for phytoremediation of HM-contaminated soils in arid regions. Innovative treatments with sulfur, EDTA, and olive mill wastewater significantly enhance soil decontamination and plant growth. Full article

To understand the characteristics of the pollution risk of potentially toxic elements (PTEs) at a rare and precious metal mining site in Guangxi and to provide scientific evidence for the comprehensive evaluation and soil remediation of PTE pollution at the site, the Cd, As, Co, Cu, Cr, Ni, Pb, and Zn contents of five areas were determined. Laboratory testing was conducted on five soil plots in the selected five suspected contaminated areas (electroplating workshop, sewage treatment area, and boiler room). Correlation analysis, infrared spectroscopy (FTIR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were used to evaluate and analyze PTE pollution. The average contents of Cd, Co, As, Pb, Zn, and Cu at the site were higher than the background values in the Guangxi soil. The Probability Mass Function (PMF) model was used to perform a source apportionment of the PTEs and determine the main pollution sources and their contribution rates. The results of the single factor pollution of the PTEs showed that Cd, Ar, and Cr were heavy pollutants, and Co was a light pollutant. The Nemerow comprehensive pollution index analysis showed that the study area was heavily polluted. The Earth accumulation index results show that Cd exhibited a very serious accumulation, Cu and Zn exhibited mild to moderate accumulations, and As and Co exhibited moderate accumulations. The FTIR results showed that C=O in the soil was chelated with PTEs in some samples, which weakened the characteristic peaks of C=O in proteins and polypeptides. The XRD results showed that cadmium hydroxide, lead oxide, and zinc hydroxide were present in the soil samples. The XPS results showed that the production of O²⁻ in the O 1s high-resolution spectra mainly came from the metal oxides produced by the polluting metals. Meanwhile, the microbial results showed that the pollution risk of PTEs affected the soil microbial community structure and diversity to some extent. Full article

Microplastics and heavy metals (HMs) in soil pose significant environmental and health risks, yet the interactions between mulch film residues and HMs, and their effects on maize productivity, remain poorly understood. This study examined the impacts of long-term traditional polyethylene mulch film (TMF) and biodegradable mulch film (BMF) residues on soil properties, maize root accumulation of HMs, the arbuscular mycorrhizal fungi (AMF) community, and maize productivity under open field conditions. TMF residues significantly increased the soil total carbon (TC), C/N ratio, and bioaccumulation coefficients (BACs) of arsenic (As) and cadmium (Cd) while lowering soil pH and water content. These changes altered AMF colonization and enriched the Paraglomus genus, leading to enhanced maize leaf antioxidant activity and reduced chlorophyll content, although maize growth was not statistically affected. In contrast, they improved soil nutrient availability (e.g., nitrogen and phosphorus), increased TC and the C/N ratio, and reduced soil pH. Notably, BMF residues decreased the BACs of As and Cd, reduced AMF spore density without altering community structure, and ultimately enhanced maize biomass. These effects were associated with BMF’s ability to lower pH and chelate HMs, thereby mitigating their bioavailability and promoting plant growth. Furthermore, the enriched abundance of AMF species, particularly from the Claroideoglomus genus, facilitated heavy metal chelation and reduced HM accumulation in plants. The findings underscore the potential of BMF and AMF for co-remediation of microplastics and HMs, highlighting the importance of mulching strategies for sustainable agriculture. Full article

The growing use of ammonium polyphosphate (APP) fertilizer requires an understanding of its soil transformation for sustainable phosphorus (P) management and environmental protection. This study investigated the adsorption characteristics of APP1 (two P species) and APP2 (seven P species) in six soils, comparing them with monoammonium phosphate (MAP). Results revealed that APP adsorption was greater than MAP under low P soil and/or low P addition condition, but was lower under high P soil and high P addition conditions. Generally, APP1 showed greater adsorption than APP2, except in laterite soil rich in iron (Fe) and aluminum (Al) oxides. Polyphosphates in APP, especially pyrophosphate, mainly contributed to total P adsorption and promoted the release of native orthophosphate in soil. Compared to MAP, APP’s chelation altered soil pH and released Fe, Al, and organic carbon, impacting P adsorption. Redundancy analysis indicated that Fe oxide and Olsen-P in acidic soils accounted for 54.5% of the variance in adsorption differences between APP and MAP, while pH and organic matter in calcareous soils explained 49.7%. In conclusion, the adsorption differences between APP and MAP depended on P concentration, APP’s P species distribution, and soil properties, providing valuable insights for optimal P management in sustainable agriculture. Full article

Many nitrogen-fixing bacteria can produce siderophores for iron acquisition in soil, but the impact of their siderophore-producing capabilities on the rhizosphere soil microecology is not well understood. To explore the effects of root inoculation with NFB strains with different siderophore-producing capabilities on the rhizosphere soil microecology and deeply evaluate the application value of a high-yielding siderophore strain in promoting crop growth, the wild-type nitrogen-fixing bacterial strain Kosakonia radicincitans GXGL-4A and its Tn5 mutants M107 (high siderophore-producing ability) and M246-2 (deficient in siderophore production) were used as biofertilizers in cucumber rhizosphere soil. Iron is important for the growth of bacterial cells, and the mutant M246-2 showed the slowest growth rate compared to the other strains when incubated in an A15 nitrogen-free medium supplied with different levels of iron. The mutant M107 had the strongest chelating ability for iron, with the largest yellow halo on the CAS detection plate. There were statistically significant differences in the halo diameters among the three NFB groups. Compared with the control group, the application of NFB significantly increased the activities of soil peroxidase and dehydrogenase and altered the soil nitrogen contents. Fertilization with the mutant M107 significantly improved the cucumber biomass and reduced the abundance and diversity of bacterial communities in the rhizosphere soil compared to the other groups. The contents of soil ammonium nitrogen and total nitrogen and soil dehydrogenase showed significant correlations with the abundance of the top 50 dominant genera in the soil. The soil TN content was the essential factor affecting the abundance of Kosakonia bacteria in the cucumber rhizosphere. Full article