Mn Accumulation Research Articles

The Role of Metal Tolerance Proteins (MTPs) Associated with the Homeostasis of Divalent Mineral Elements in Ga-Treated Rice Plants.

Mineral elements typically act as transported substrates for metal tolerance proteins (MTPs). The chelation of MTPs with heavy metal ions is a suggestive detoxification pathway in plants; therefore, the trade-off between transporting mineral elements and chelating excess toxic metal ions is inevitable. Gallium (Ga) is an emerging pollutant associated with high-tech industries. This study investigated the impact of Ga stress on MTPs, subsequently altering the transport and distribution of mineral elements. Gallium exposure reduced rice seedling biomass, with roots accumulating more Ga than shoots. Ga stress also changed the rice plants' subcellular mineral element distribution. PCR assays showed that Ga stress negatively affected all genes belonging to the Mn group, except OsMTP9. While Mn accumulation in the rice cellular compartments did not respond positively to Ga stress, OsMTP8, OsMTP8.1, OsMTP11, and OsMTP11.1 were found to be intimately connected to Mn transport and repressed by increased Ga accumulation in roots. Mg and Cu accumulated in the cytosol and organelles of Ga-treated rice plants, while OsMTP9 expression increased, demonstrating its importance in transporting Mg and Cu. A positive link between Ga stress and Zn accumulation in the cytosol and organelles was found, and OsMTP7 and OsMTP12 expression was positive, suggesting that Ga stress did not impair their Zn transport. Notably, Ga exposure down-regulated Fe-transporting OsMTP1 and OsMTP6, wherein the subcellular concentrations of Fe showed negative responses to Ga accumulation. These findings provide valuable insights into elucidating the roles of OsMTPs in Ga tolerance and the transport of these mineral elements.

Hyperaccumulation of metal in the apoplast contributes to the tolerance of the phytoremediator Pistia stratiotes L. to manganese-contaminated water

Phytoremediation of manganese (Mn)-contaminated water requires the selection of Mn-tolerant species. This study reports on physiological changes and Mn bioaccumulation in the aquatic macrophyte Pistia stratiotes cultivated under various MnCl2 concentrations: control, 80, 340, 600, 1000, 2000, and 4000 µM. Few visual symptoms of Mn toxicity, such as chlorosis, were observed after 10 days, especially in plants treated with 2000 and 4000 µM MnCl2. High Mn accumulation was recorded, with maximum values of 23,700 and 24,600 µg g−1 DW in the shoots and roots, respectively, at 4000 µM Mn, contrasting with 825.01 and 1587.53 µg g−1 DW in control plants. Cellular fractioning showed that Mn in shoots and roots was mainly associated with the cell wall, with approximately 90% of the Mn in roots detected in the apoplast. There were no significant changes in net CO2 assimilation or respiratory rates after 5 and 10 days of Mn exposure. These results demonstrate that P. stratiotes is a Mn hyperaccumulator species with excellent phytoremediation potential, as shown by its high bioaccumulation capacity and its ability to maintain photosynthetic efficiency under Mn stress.

GmSTOP1-3 Increases Soybean Manganese Accumulation Under Phosphorus Deficiency by Regulating GmMATE2/13 and GmZIP6/GmIREG3.

Mineral nutrient deficiencies and metal ion toxicities coexist on acid soils. Phosphorus (P) deficiency in plants is generally accompanied with significant levels of leaf manganese (Mn) accumulation. However, the molecular regulatory mechanisms underpinning remain unclear. The present study found that P-deficient soybean plants accumulated more Mn compared to P-sufficient ones on acid soils in both field and greenhouse experiments. Meanwhile, both P deficiency and Mn toxicity enhanced the expression of GmSTOP1-3. Over-expressing GmSTOP1-3 enhanced Mn accumulation in transgenic soybean hairy roots, but RNA-interference did not show obvious differences. Moreover, transgenic soybeans with GmSTOP1-3-overexpression showed enhanced root citrate exudation and augmented Mn accumulation. RNA-sequence identified four downstream genes of GmSTOP1-3, including multidrug and toxic compound extrusion (GmMATE2/13) and metal transporter genes (GmZIP6/GmIREG3), which encode plasma membrane proteins. GmSTOP1-3 activated the transcription of these four genes by directly binding to their promoter regions. In addition, both GmZIP6 and GmIREG3 functioned in Mn uptake as manifested by the higher Mn concentration and decreased growth of soybean hairy roots with their overexpression. Taken together, it is suggested that upregulation of GmSTOP1-3 by low P stress on acid soils activates transcripts of GmMATE2/13 and GmZIP6/GmIREG3, which consequently result in enhanced Mn accumulation in soybean.

Study of excess manganese stress response highlights the central role of manganese exporter Mnx for holding manganese homeostasis in the cyanobacterium Synechocystis sp. PCC 6803.

Cellular levels of the essential micronutrient manganese (Mn) need to be carefully balanced within narrow borders. In cyanobacteria, a sufficient Mn supply is critical for ensuring the function of the oxygen-evolving complex as the central part of the photosynthetic machinery. However, Mn accumulation is fatal for the cells. The reason for the observed cytotoxicity is unclear. To understand the causality behind Mn toxicity in cyanobacteria, we investigated the impact of excess Mn on physiology and global gene expression in the model organism Synechocystis sp. PCC 6803. We compared the response of the WT and the knock-out mutant in the Mn exporter (Mnx), ∆mnx, which is disabled in the export of surplus Mn and thus functions as a model for toxic Mn overaccumulation. While growth and pigment accumulation in ∆mnx were severely impaired 24 h after the addition of tenfold Mn, the WT was not affected and thus mounted an adequate transcriptional response. RNA-seq data analysis revealed that the Mn stress transcriptomes partly resembled an iron limitation transcriptome. However, the expression of iron limitation signature genes isiABDC was not affected by the Mn treatment, indicating that Mn excess is not accompanied by iron limitation in Synechocystis. We suggest that the ferric uptake regulator, Fur, gets partially mismetallated under Mn excess conditions and thus interferes with an iron-dependent transcriptional response. To encounter mismetallation and other Mn-dependent problems on a protein level, the cells invest in transcripts of ribosomes, proteases and chaperones. In the case of the ∆mnx mutant, the consequences of the disability to export excess Mn from the cytosol manifest in additionally impaired energy metabolism and oxidative stress transcriptomes with a fatal outcome. This study emphasizes the central importance of Mn homeostasis and the transporter Mnx's role in restoring and holding it.

Combination of Silicate-Based Soil Conditioners with Plant Growth-Promoting Microorganisms to Improve Drought Stress Resilience in Potato.

Due to shallow root systems, potato is a particularly drought-sensitive crop. To counteract these limitations, the application of plant growth-promoting microorganisms (PGPMs) is discussed as a strategy to improve nutrient acquisition and biotic and abiotic stress resilience. However, initial root colonization by PGPMs, in particular, can be affected by stress factors that negatively impact root growth and activity or the survival of PGPMs in the rhizosphere. In this study, perspectives for the use of commercial silicate-based soil conditioners (SCs) supposed to improve soil water retention were investigated. The SC products were based on combinations with lignocellulose polysaccharides (Sanoplant® = SP) or polyacrylate (Geohumus® = GH). It was hypothesized that SC applications would support beneficial plant-inoculant interactions (arbuscular mycorrhiza, AM: Rhizophagus irregularis MUCL41833, and Pseudomonas brassicacearum 3Re2-7) on a silty loam soil-sand mixture under water-deficit conditions (6-12 weeks at 15-20% substrate water-holding capacity, WHC). Although no significant SC effects on WHC and total plant biomass were detectable, the SC-inoculant combinations increased the proportion of leaf biomass not affected by drought stress symptoms (chlorosis, necrosis) by 66% (SP) and 91% (GH). Accordingly, osmotic adjustment (proline, glycine betaine accumulation) and ROS detoxification (ascorbate peroxidase, total antioxidants) were increased. This was associated with elevated levels of phytohormones involved in stress adaptations (abscisic, jasmonic, salicylic acids, IAA) and reduced ROS (H2O2) accumulation in the leaf tissue. In contrast to GH, the SP treatments additionally stimulated AM root colonization. Finally, the SP-inoculant combination significantly increased tuber biomass (82%) under well-watered conditions, and a similar trend was observed under drought stress, reaching 81% of the well-watered control. The P status was sufficient for all treatments, and no treatment differences were observed for stress-protective nutrients, such as Zn, Mn, or Si. By contrast, GH treatments had negative effects on tuber biomass, associated with excess accumulation of Mn and Fe in the leaf tissue close to toxicity levels. The findings suggest that inoculation with the PGPMs in combination with SC products (SP) can promote physiological stress adaptations and AM colonization to improve potato tuber yield, independent of effects on soil water retention. However, this does not apply to SC products in general.

Assessment of manganese accumulation in dryland wheat grains via plastic film mulching: Implications for human health risk in multi-site studies

Crop manganese (Mn) accumulation and the associated human health risks stemming from excessive intake of high Mn crop foods have attracted attention. However, there is limited information available concerning the impact of plastic film mulching (PFM) on Mn concentration in cereal grains and the health risks associated with Mn intake by the human body. Field experiments were conducted from 2014 to 2016 at seven sites in the drylands of a typical wheat-growing region in China to assess the effect of PFM on grain Mn concentration, Mn accumulation and distribution in winter wheat plants, and the potential risk of Mn intake and optimal grain intake for human health. The multi-site study results revealed that grain Mn concentration and bioavailability were significantly higher under PFM compared to no mulching. Similarly, PFM was found to enhance aboveground Mn accumulation at the anthesis stage by 17.5 %, Mn harvest index by 3.9 %, grain Mn accumulation by 28.9 %, and available Mn concentration in the soil by 10.9 %. The increased uptake and accumulation of Mn in wheat plants, leading to elevated grain Mn concentration, were primarily attributed to the improved availability of Mn and moisture in the soil under PFM treatment. Furthermore, a health risk assessment indicated that long-term consumption of whole wheat grains from PFM treatment could potentially pose a non-carcinogenic risk of Mn for children and adolescents residing in rural areas. Therefore, this study established upper limits for daily consumption of whole wheat grains based on the specific needs of local residents. The findings of this research underscore the potential health risks associated with consuming grain crops grown in PFM crop production systems.

Heavy metals toxicity in edible bivalves and risk exposure to humans through its consumption from Adyar Estuary, Tamilnadu, India – A baseline study

The Adyar estuary, situated at the heart of Chennai city, India, has been subjected to significant anthropogenic pollution over the past decade due to rapid urbanization and industrialization.This study endeavored to explore the bioaccumulation patterns of heavy metals within bivalve species including Perna viridis, Mercenaria mercenaria, and Lamellidens marginalis. Additionally, it aimed to assess the concentrations of heavy metals present in water samples obtained from ten discrete stations within the Adyar estuary across different seasonal periods. To better understand the dynamics of contamination, metal pollutants including Cd, B, Cu, Fe, Mn, Pb, and Zn were analyzed in the soft tissues (Gill, Kidney, and Muscle) of the bivalves using Atomic Absorption Spectrophotometer (AAS) (ELICO's SL- 176). The study also investigated the seasonal changes in biochemical constituents affecting the nutritional quality of these edible bivalves following conventional methods, and estimated the risk (both carcinogenic and non-carcinogenic) to consumers. Results showed that the biochemical constituents of Perna viridis and Mercenaria mercenaria were comparatively lower than those of the freshwater bivalve Lamellidens Marginalis (p > 0.05). Heavy metal accumulation in the mussels followed the order Mn > Zn > Cu > Pb > Fe > Cd > B. The highest uptake of metals by the bivalves occurred during the post-monsoon season, while the least uptake was observed during the monsoon season. The overall metal burden for the studied species followed the descending order M. mercenaria >P. viridis >L. marginalis. The study indicated that both carcinogenic and non-carcinogenic risks to humans from consuming these mussels were higher due to the excessive accumulation of metals Zn and Mn in all three studied bivalves.

Mn-CDF family genes enhance the manganese tolerance of the tea plants (Camellia sinensis) under acidic condition

The tea plants cultivated in acidic soils are vulnerable to excessive manganese (Mn), which increases the risk of Mn2+ toxicity to physiology and development. Mn-cation diffusion facilitator (CDF) family genes have been implicated in regulating Mn homeostasis and tolerance. However, the mechanism of Mn tolerance of tea plants in acidic environments is still unknown. In this study, we initially examined the phenotypic characteristics and Mn contents variability in different tissues of tea plants under various Mn concentration at pH 5 and 4. We observed that tea plants exhibited remarkably high Mn tolerance at pH 4, with Mn accumulation notably elevated in the aboveground tissues under pH 4 condition after 28-day treatment. We found the expression levels of Mn-CDF genes, had different subcellular localization, were tissue-specific and significantly induced by high Mn concentrations at pH 4 condition. Furthermore, the yeast complementation assays indicated that the heterologous expression of Mn-CDF genes restored the growth of a Mn2+ sensitive yeast strain, Δpmr1. Taken together, these results suggest that Mn-CDF family genes function as Mn transporters to participate in Mn tolerance in acidic environments. This study provides reference for further study on the mechanism of maintaining Mn homeostasis in tea plants under soil acidification.

Variation of Elemental Composition of Leaves in Nitraria schoberi L. and N. sibirica Pall. Depending on Edaphic Growth Conditions

A study was conducted about the variation of levels of macro- and microelements in the soil and leaves of two species of the genus Nitraria L. in various habitats in Siberia. New data were obtained on the concentration variations of K, Na, Ca, Mg, Fe, Mn, Zn, Cu, Ni, Li, Sr, and Cd in leaves of N. schoberi L. and N. sibirica Pall. It was found that the salinity of habitats of N. sibirica (up to 3.23%) can exceed salinity of soils under N. schoberi (up to 0.5%) by more than sixfold. Soils of N. schoberi habitats are characterized by lower contents of carbonates (1.0–3.8%) and of physical clay (2–19%) as compared to soils of N. sibirica habitats: 1.2–18.2 and 9–40%, respectively. An increase in the physical-clay content of soil positively correlated with the accumulation of Mg, Cu (p ≤ 0.01), and Mn (p ≤ 0.001) in the plant leaves. The degree of soil salinity was positively associated with the accumulation of Ca, Zn, Sr (p ≤ 0.01), Mg (p ≤ 0.05), and Cd (p ≤ 0.001) in the leaves. An increase in concentration of mobile Na in soil positively correlated with concentrations of Ca, Cu (p ≤ 0.01), and Zn (p ≤ 0.001) in the leaves. In N. sibirica leaves, the concentration of K, Ca, Mg, Fe, Sr, Mn, Zn, and Cu was 1.5–3 times higher than that in N. schoberi leaves. Both species are capable of accumulating very high concentrations of Na (N. schoberi: up to 83.8 g/kg and N. sibirica: up to 77.2 g/kg). In the leaves of N. schoberi plants of immature age, K and Na levels were seven times higher than those in leaves of adult generative plants, whereas Mg and Ca levels were 3–5 times higher. This study should expand the understanding of mechanisms of Nitraria species’ adaptation to high-salinity conditions.

Effects of mixed metal exposure on MRI metrics in basal ganglia.

Welding fumes contain various metals. Past studies, however, mainly focused on Manganese (Mn)-related neurotoxicity. This study investigated welding-related mixed metal exposure effects on MRI metrics in the basal ganglia (BG) and their dose-response relationship. Subjects with (N = 23) and without (N = 24) a welding exposure history were examined. Metal exposure was estimated with an exposure history questionnaire and whole blood metal levels. T1 (weighted-intensity and relaxation time; estimates of brain Mn accumulation), diffusion tensor imaging (axial [AD], mean [MD], radial diffusivity, and fractional anisotropy [FA]; estimates of microstructural differences) metrics in BG (caudate nucleus, putamen, and globus pallidus [GP]), and voxel-based morphometry (for volume) were examined and related with metal exposure measures. Compared with controls, welders showed higher GP R1 (1/T1; P = 0.034) but no differences in blood metal and T1-weighted (T1W) values in any ROIs (P's > 0.120). They also had higher AD and MD values in the GP (P's < 0.033) but lower FA values in the putamen (P = 0.039) with no morphologic differences. In welders, higher blood Mn and Vanadium (V) levels predicted higher BG R1 and T1W values (P's < 0.015). There also were significant overall metal mixture effects on GP T1W and R1 values. Moreover, GP AD and MD values showed nonlinear associations with BG T1W values: They increased with increasing T1W values only above certain threshold of T1 values. The current findings suggest that Mn and V individually but also metal mixtures jointly predict GP T1 signals that may in turn contribute to altered DTI metrics in the BG after certain exposure threshold levels.

Expression of Manganese Transporters ZIP8, ZIP14, and ZnT10 in Brain Barrier Tissues.

Manganese (Mn) is an essential trace mineral for brain function, but excessive accumulation can cause irreversible nervous system damage, highlighting the need for proper Mn balance. ZIP14, ZnT10, and ZIP8 are key transporters involved in maintaining Mn homeostasis, particularly in the absorption and excretion of Mn in the intestine and liver. However, their roles in the brain are less understood. The blood-cerebrospinal fluid barrier and the blood-brain barrier, formed by the choroid plexus and brain blood vessels, respectively, are critical for brain protection and brain metal homeostasis. This study identified ZIP14 on the choroid plexus epithelium, and ZIP8 and ZnT10 in brain microvascular tissue. We show that despite significant Mn accumulation in the CSF of Znt10 knockout mice, ZIP14 expression levels in the blood-cerebrospinal fluid barrier remain unchanged, indicating that ZIP14 does not have a compensatory mechanism for regulating Mn uptake in the brain in vivo. Additionally, Mn still enters the CSF without ZIP14 when systemic levels rise. This indicates that alternative transport mechanisms or compensatory pathways ensure Mn balance in the CSF, shedding light on potential strategies for managing Mn-related disorders.

Welding techniques and manganese concentrations in blood and brain: Results from the WELDFUMES study

This study used whole-brain mapping to investigate the effect of different welding processes on manganese (Mn) accumulation in the brain. Exposure measurements were performed at the welders’ workplaces about 3 weeks before a magnetic resonance imaging (MRI) examination. The welders were categorized into three main groups based on welding method, and the T1-relaxation rate (R1) was measured using quantitative MRI (qMRI). Welders using shielded metal arc welding (SMAW) were found to have lower accumulations of total Mn in clusters encompassing white matter, thalamus, putamen, pallidum, and substantia nigra compared with welders using inert gas tungsten arc welding (GTAW) or continuous consumable electrode arc welding (CCEAW). A positive correlation was found between Mn in red blood cells (Mn-RBC) and R1 in a region encompassing pre-and post-central gyri. The results of this study show that the accumulation of free, bound, or compartmentalized Mn ions in the brain differed depending on the welding method used. These differences were predominately located in the basal ganglia but were also found in regions encompassing white matter. The level of Mn-RBC was correlated to the deposition of Mn in the left primary somatosensory and motor cortex and may therefore be linked to neurological and neurobehavioral symptoms.

Hormetic responses to cadmium exposure in wheat seedlings: insights into morphological, physiological, and biochemical adaptations.

Cadmium is commonly recognized as toxic to plant growth, low-level Cd has promoting effects on growth performance, which is so-called hormesis. Although Cd toxicity in wheat has been widely investigated, knowledge of growth response to a broad range of Cd concentrations, especially extremely low concentrations, is still unknown. In this study, the morphological, physiological, and biochemical performance of wheat seedlings to a wide range of Cd concentrations (0-100 µΜ) were explored. Low Cd treatment (0.1-0.5µM) improved wheat biomass and root development by enhancing the photosynthetic system and antioxidant system ability. Photosynthetic rate (Pn) was improved by 5.72% under lower Cd treatment (1 µΜ), but inhibited by 6.05-49.85% from 5 to 100 µΜ. Excessive Cd accumulation induced oxidative injury manifesting higher MDA content, resulting in lower photosynthetic efficiency, stunted growth, and reduction of biomass. Further, the contents of ascorbate, glutathione, non-protein thiols, and phytochelatins were improved under 5-100 µΜ Cd treatment. The ascorbate peroxidase activity in the leaf showed a hormetic dose-response characteristic. Correlation analysis and partial least squares (PLS) results indicated that antioxidant enzymes and metabolites were closely correlated with Cd tolerance and accumulation. The results of the element network, correlation analysis, and PLS showed a crucial role for exogenous Cd levels in K, Fe, Cu, and Mn uptake and accumulation. These results provided a deeper understanding of the hormetic effect of Cd in wheat, which would be beneficial for improving the quality of hazard and risk assessments.

Macrophytes as Bioindicators of Heavy Metal Pollution in Belarusian Rivers

ABSTRACTMacrophytes are well‐known for accumulating a large number of various substances, including metals, and they may consequently serve as biogeochemical indicators of aquatic system pollution. In general, the sequence of analyzed metal accumulation in river macrophytes is as follows (mg/kg): Mn (141) &gt; Cu (2.53) &gt; V (0.89) &gt; Cr (0.70) &gt; Pb (0.68) &gt; Ni (0.23). Submersed species are conspicuous for their increased metal accumulation capacity, with statistically significant differences compared to other ecological groups. Among the aquatic plant genera examined (Potamogéton, Ceratophýllum, Elodea, Núphar, Butomus, Glycéria, and Spargánium), an increased capacity to accumulate Mn, Cu, and Pb is observed in all submersed macrophytes, while Cr, V, and Ni are particularly accumulated by Ceratophýllum and Elodea. Potamogéton has the largest range of V, Cr, Mn, Ni, and Cu variations. The overall bioaccumulation capability evaluated by the metal accumulation index was ordered as follows: Núphar (6.94) &gt; Potamogéton (5.53) &gt; Butomus (3.48) &gt; Glycéria (2.86) &gt; Spargánium (2.62) &gt; Elodea (2.33) &gt; Ceratophýllum (1.98). Bio‐accumulation factors (BAFs) (macrophytes/sediment) vary depending on the metal and macrophyte ecological groups. For submersed macrophytes, the sequence of BAFs is Mn &gt; Cu &gt; Ni &gt; Pb &gt; Cr &gt; V. In the submersed plants of watercourses taken at the anthropogenic impact sites, the accumulation of Ni, V, Mn, Pb, and Cu is statistically significantly higher compared to those in natural conditions. Compositional data analysis has revealed such biogeochemical signatures of the anthropogenic impact as the formation of the anthropogenic Cr–Ni association, which is associated with the identified multivariate anomalies, as well as an increase in Cu variability and a decrease in Mn.

Effects of SpGSH1 and SpPCS1 overexpression or co-overexpression on cadmium accumulation in yeast and Spirodela polyrhiza

Cadmium (Cd) is one of the most toxic elements to all organisms. Glutathione (GSH)-dependent phytochelatin (PC) synthesis pathway is considered an extremely important mechanism in Cd detoxification in plants. However, few studies have focused on the roles of glutamate-cysteine ligase (GSH1) and phytochelatin synthase (PCS1) in Cd accumulation and detoxification in plants. In this study, SpGSH1 and SpPCS1 were identified and cloned from Spirodela polyrhiza and analyzed their functions in yeast and S. polyrhiza via single- or dual-gene (SpGP1) overexpression. The findings of this study showed that SpGSH1, SpPCS1, and SpGP1 could dramatically rescue the growth of the yeast mutant Δycf1. In S. polyrhiza, SpGSH1 was located in the cytoplasm and could promote Mn and Ca accumulation. SpPCS1 was located in the cytoplasm and nucleus, mainly expressed in meristem regions, and promoted Cd, Fe, Mn, and Ca accumulation. SpGSH1 and SpPCS1 co-overexpression increased the Cd, Mn, and Ca contents. Based on the growth data of S. polyrhiza, it was recommended that biomass as the preferable indicator for assessing plant tolerance to Cd stress compared to frond number in duckweeds. Collectively, this study for the first time systematically elaborated the function of SpGSH1 and SpPCS1 for Cd detoxification in S. polyrhiza.

Mineralisation controls for the diverse Cape manganese occurrences, South Africa

Abstract The Cape Fold Belt, comprising folded sedimentary sequences from predominantly the Palaeozoic Cape Supergroup, hosts a multitude of manganese occurrences and mineral deposits, many of which were subject to historical mining activity. Although size, grade and quality issues negate their modern-day exploitation for the steel-making process, the mechanisms by which Mn has enriched at these sites holds scientific value for our understanding of low-temperature Mn (bio-)geochemical cycling. Deposits located within the Cape Fold Belt comprise structure-hosted Mn deposits and a little described class of Mn mound deposits associated with chalybeate thermal springs (temperature = 41 to 48°C). Although the relationships between the two remain tenuous, detailed study of both classes provides insight into the conditions that favour Mn accumulation in the near-surface and sub-aerial environments. Comparisons between the physicochemistry of manganiferous- and non-manganiferous thermal springs suggest that manganese solubility is favoured by warm, acidic and slightly reducing fluids with elevated salinity. Transport, and associated fluid focusing typically within highly permeable sandstone units, serves to locate Mn mineralisation in near-surface structurally-complex trap sites that provide both accommodation space and conditions that are sufficiently oxidising. Where manganiferous spring waters spill out at surface, oxidation is caused by contact with atmospheric O2 to form Mn mound deposits, and ambient Mn-oxidising microbiota (e.g., genus Ramlibacter, and members of Burkholderiales, Rhodocyclaceae, and Oxalobacteraceae) are likely to play a role in enhancing the kinetics of this process. Relative to the structure-hosted deposits, these Mn mound deposits are typically lower grade (higher iron content) and relatively friable (high porosity and fine grain sizes). Supergene and diagenetic processes can lead to localised upgrade of the Mn mound material, although typically not to ore grade.

Phosphorus-induced restructuring of the ascorbate-glutathione cycle and lignin biosynthesis alleviates manganese toxicity in peach roots.

Manganese (Mn) is indispensable for plant growth, but its excessive uptake in acidic soils leads to toxicity, hampering food safety. Phosphorus (P) application is known to mitigate Mn toxicity, yet the underlying molecular mechanism remains elusive. Here, we conducted physiological and transcriptomic analyses of peach roots response to P supply under Mn toxicity. Manganese treatment disrupted root architecture and caused ultrastructural damage due to oxidative injury. Notably, P application ameliorated the detrimental effects and improved the damaged roots by preventing the shrinkage of cortical cells, epidermis and endodermis, as well as reducing the accumulation of reactive oxygen species (ROS). Transcriptomic analysis revealed the differentially expressed genes enriched in phenylpropanoid biosynthesis, cysteine, methionine and glutathione metabolism under Mn and P treatments. Phosphorus application upregulated the transcripts and activities of core enzymes crucial for lignin biosynthesis, enhancing cell wall integrity. Furthermore, P treatment activated ascorbate-glutathione cycle, augmenting ROS detoxification. Additionally, under Mn toxicity, P application downregulated Mn uptake transporter while enhancing vacuolar sequestration transporter transcripts, reducing Mn uptake and facilitating vacuolar storage. Collectively, P application prevents Mn accumulation in roots by modulating Mn transporters, bolstering lignin biosynthesis and attenuating oxidative stress, thereby improving root growth under Mn toxicity. Our findings provide novel insights into the mechanism of P-mediated alleviation of Mn stress and strategies for managing metal toxicity in peach orchards.

Dynamics of Fe, Mn, and potentially harmful elements under reducing conditions in iron ore tailings after dam collapse in the Doce River basin-Brazil: flooded and non-flooded rice cultivations.

Potentially harmful element (PHE) bioavailability is important to environmental contamination and must be checked under several soil conditions. This study aimed to assess Fe, Mn, and PHE uptake by rice (Oryza sativa) grown on flooded and non-flooded Fe tailings collected from the Doce River basin after its collapse in Brazil. After 65days of sowing, shoots and roots were harvested to determine PHE concentrations. The mean concentrations of Mn in shoots and Fe in the roots of rice grown on the flooded tailings were 2140mgkg-1 and 15,219mgkg-1, respectively. Mn was extensively translocated from roots to shoots (translocation factor (TF) = 2). Conversely, Fe accumulated in roots (TF = 0.015) and caused morphological damage to this rice organ. The application of macro and micronutrients lessened Fe toxicity in the roots of rice cultivated on the flooded tailings. The flooding of tailings influenced more Fe accumulation than Mn accumulation by rice plants. The PHE Ag, As, Cd, Ni, Hg, Pb, and Sb exhibited low total concentrations (maximum of 9mgkg-1 for Ni and a minimum of 0.2mgkg-1 for Cd, Hg, and Sb), and it was not observed an increase in their availability under tailings flooding conditions.

Elemental profiling of agricultural soil in Hoshiarpur utilizing analytical techniques.

Our study aimed to assess the soil quality in Punjab's Hoshiarpur district through a meticulous analysis of nutrient and elemental composition. Using a variety of analytical techniques, including Neutron Activation Analysis (NAA), external Particle-induced Gamma-ray Emission (PIGE) an Ion beam analysis Technique, and energy-dispersive X-ray fluorescence (ED-XRF), we delved into soil characterization for 22 agricultural soil samples in the Punjab region. Within the NAA framework, utilizing the Pneumatic Carrier Facility and the self-serve facility at Dhruva reactor in Mumbai, a brief 1-min irradiation procedure identified pivotal elements-Na, Mg, V, Al, Mn, and K. Conversely, an extended neutron irradiation process of approximately 4h within the self-serve facility enabled the estimation of nearly 12 elements, including Rare Earth Elements (REEs), Transition elements, and other significant elements. The external PIGE technique quantified low Z elements (Na, Mg, Al, and Si), contributing to our analytical arsenal. Rigorously validating both NAA and PIGE methodologies, we compared results meticulously against established geological standard reference materials-specifically USGS RGM-1 and USGS AGV-1.Instrumental in elemental analysis, ED-XRF spectroscopy fortified our investigative endeavors by quick assessment of ten crucial elements. The elemental analysis revealed notable accumulations of Mn and Zn in the soil, surpassing the suggested permissible limits, whereas Co, Cr, and Pb were found to be within the recommended thresholds set by WHO/UNEP. Beyond elemental profiling, our study extended to estimate the accumulation levels of various elements utilizing ecological risk factors such as Contamination Factor, Potential Ecological Risk Index, Pollution Load Index, and Geoaccumulation Factor. Our findings highlighted significant accumulation of REEs including La, Sm and Yb.. This evaluation sheds new light on the interplay between soil composition and environmental health, emphasizing the need for advanced accessible agricultural technologies to prevent and forecast contaminant discharge in arable soil. This commitment aligns with our broader goal of advancing sustainable practices in soil management.

Profiling and health risk assessment of trace metal contents in bovine tissues: A case study in Gondar City, Ethiopia

This study aimed to determine six trace metal (Cu, Mn, Zn, Cd, Cr, and Pb) concentrations in three bovine tissues (kidney, liver and muscle) from Gondar City abattoir, Ethiopia, and assess associated health risks. Samples were digested with HNO3/HClO4, and metal concentrations were analyzed by Inductively Coupled Plasma Optical Emission Spectroscopy. Zn exhibited the highest concentration in muscle (52.1 mg/kg), whereas Cd was below the LOD (0.6 µg/kg) in all muscle samples. The levels of Cd, Cr, and Mn in liver and kidney tissues, as well as Zn in muscle, exceeded FAO/WHO safety thresholds. Principal component analysis revealed distinct metal accumulation patterns among the tissues where liver is the target organ for accumulation of Pb, Mn and Cu, while kidney appears to be the organ of preference for Cd and Cr accumulation. Zn had the highest chronic daily intake for both children and adults, followed by Cu. Hazard index values for both age groups were below one, indicating no non-carcinogenic risks. However, the incremental lifetime cancer risks and cumulative carcinogenic risks of Cr exceeded the tolerable limit for adults and children, indicating a high cancer likelihood from this trace metal. In contrast, the incremental lifetime cancer risks of Pb for both adults and children were within acceptable limits. In conclusion, cumulative carcinogenic risk values indicate that consuming muscle tissue poses health risks for both adults and children, highlighting the need for stricter cattle feed regulations in the study area to safeguard public health.