Mn Treatment Research Articles

Influence of Manganese on Nutrient Uptake in Rice Plants under Saline Conditions

Salinity-induced nutritional disorders adversely affect the performance of crops. The consequence of salinity disorders may result on nutrient availability, competitive uptake, transport or partitioning within the plants. Present study was aimed to investigate the effects of Mn application on nutrient uptake contributing to the salinity tolerance of the rice. A hydroponic experiment was carried out in National Agriculture Research Centre, Islamabad, Pakistan, on two rice varieties. Three NaCl salt concentrations, namely 0, 25, 50 mmol were used. Manganese sulphate was used for foliar and root application with four concentrations (0, 2, 4, 8 mg Mn L-1). Salinity decreased the uptake of P, K, Ca, Mg, Mn and Zn in both applications methods while application of Mn increased the uptake of almost all the investigated macro and micronutrients. Root applications of Mn and foliar application methods were compared where root application method was found better for most of the nutrient uptake. Interaction effect i.e salinity × Mn treatment × methods of application was significant. The results showed that Mn application can improve the nutrient uptake capability contributing to the salinity tolerance in rice.

Response of litter decomposition and the soil environment to one-year nitrogen addition in a Schrenk spruce forest in the Tianshan Mountains, China

Human activities have increased the input of nitrogen (N) to forest ecosystems and have greatly affected litter decomposition and the soil environment. But differences in forests with different nitrogen deposition backgrounds. To better understand the response of litter decomposition and soil environment of N-limited forest to nitrogen deposition. We established an in situ experiment to simulate the effects of N deposition on soil and litter ecosystem processes in a Picea schrenkiana forest in the Tianshan Mountains, China. This study included four N treatments: control (no N addition), low N addition (LN: 5 kg N ha−1 a−1), medium N addition (MN: 10 kg N ha−1 a−1) and high N addition (HN: 20 kg N ha−1 a−1). Our results showed that N addition had a significant effect on litter decomposition and the soil environment. Litter mass loss in the LN treatment and in the MN treatment was significantly higher than that in the control treatment. In contrast, the amount of litter lost in the HN treatment was significantly lower than the other treatments. N application inhibited the degradation of lignin but promoted the breakdown of cellulose. The carbon (C), N, and phosphorus (P) contents of litter did not differ significantly among the treatments, but LN promoted the release of C and P. Our results also showed that soil pH decreased with increasing nitrogen application rates, while soil enzyme activity showed the opposite trend. In addition, the results of redundancy analysis (RDA) and correlation analyses showed that the soil environment was closely related to litter decomposition. Soil enzymes had a positive effect on litter decomposition rates, and N addition amplified these correlations. Our study confirmed that N application had effects on litter decomposition and the soil environment in a N-limited P. schrenkiana forest. LN had a strong positive effect on litter decomposition and the soil environment, while HN was significantly negative. Therefore, increased N deposition may have a negative effect on material cycling of similar forest ecosystems in the near future.

Remediation effect of mercapto-palygorskite combined with manganese sulfate on cadmium contaminated alkaline soil and cadmium accumulation in pak choi (Brassica chinensis L.)

Cadmium pollution in alkaline soil in some areas of northern China seriously threatens agricultural production and human health, but there are few materials and methods to remediate cadmium pollution in alkaline soil. Therefore, it is necessary to further study the economic and adaptive remediation and regulation techniques of cadmium pollution in alkaline soil. In the study, a pot experiment was conducted to study the effects of MP and MnSO4 combined treatment on the immobilization effect of cadmium contaminated alkaline soils. The results showed that LM and HM treatments in different periods had little effect on the content of extractable Cd fraction in soil without MP treatment, but the EXC–Cd content in the soil with Mn(15) was lower than that in the soil with Mn(29). The EXC–Cd content under MP+ LM and MP + HM treatments reduced by 3%–7% and 7%–9%, respectively. The OX–Cd content increased by 13%–16% after MP + Mn treatment. The content of DTPA–Cd decreased by 17.9%–28.6% under MP + Mn treatment except for MP + HM(15). Under the treatment of MP, LM(29), HM, MP + LM and MP + HM, the content of Cd in shoots of pak choi were decreased by 27.2%, 13.1%, 19.8%–27.9%, 28.5%–54.2% and 34.2%–41.1%, respectively. Compared with CK, the TFCd values in HM(15), LM(29), HM(29), MP + LM(29) and MP + HM(29) treatments were reduced to 35.7%, 41.1%, 35.7%, 42.9% and 37.5%, respectively, while no statistical difference was observed in other treatments. There was no significant difference in BCFCd between MP(15) and LM(15), but the BCFCd was significantly decreased. For MP + MnSO4 treatment group, the content of Mn oxides in soil was negatively correlated with the content of EXC–Cd (P < 0.05) and positively correlated with the content of OX–Cd (P < 0.05).

Preventive treatment with sodium para-aminosalicylic acid inhibits manganese-induced apoptosis and inflammation via the MAPK pathway in rat thalamus

Excessive exposure to manganese (Mn) may lead to neurotoxicity, referred to as manganism. In several studies, sodium para-aminosalicylic acid (PAS-Na) has shown efficacy against Mn-induced neurodegeneration by attenuating the neuroinflammatory response. The present study investigated the effect of Mn on inflammation and apoptosis in the rat thalamus, as well as the underlying mechanism of the PAS-Na protective effect. The study consisted of sub-acute (Mn treatment for 4 weeks) and sub-chronic (Mn and PAS-Na treatment for 8 weeks) experiments. In the sub-chronic experiments, pro-inflammatory cytokines, namely tumor necrosis factor α (TNF-α), interleukin 1β (IL-1β), and cyclooxygenase 2 (COX-2) were significantly increased in the Mn-exposed group compared to the control II. PAS-Na treatment led to a significant reduction in the Mn-induced neuroinflammation by inhibiting IL-1β and COX-2 mRNA expression and reducing IL-1β secretion and JNK/p38 MAPK pathway activity. Furthermore, immunohistochemical analysis showed that the expression of caspase-3 was significantly increased in both the sub-acute and sub-chronic experimental paradigms concomitant with a significant decrease in B-cell lymphoma 2 (Bcl-2) in the thalamus of Mn-treated rats. PAS-Na also decreased the expression levels of several apoptotic markers downstream of the MAPK pathway, including Bcl-2/Bax and caspase-3, while up-regulating anti-apoptotic Bcl-2 proteins. In conclusion, Mn exposure led to inflammation in the rat thalamus concomitant with apoptosis, which was mediated via the MAPK signaling pathway. PAS-Na treatment antagonized effectively Mn-induced neurotoxicity by inhibiting the MAPK activity in the same brain region.

The m6A mRNA demethylase FTO regulates GnRH secretion in Mn-induced precocious puberty

The GABAA receptor (GABAAR) plays important roles in the regulation of Mn-induced GnRH secretion in immature female rats. However, the underlying molecular mechanisms remain unknown. Here, we assessed whether FTO and its substrate m6A are correlated with GABAAR expression in GnRH neurons after treatment with Mn in vitro and in vivo. Our study indicated that Mn treatment increased the expression of GnRH mRNA and decreased the levels of GABAAR protein but had no effect on GABAAR mRNA. Moreover, Mn upregulated the levels of FTO and inhibited global cellular m6A levels and GABAAα2 mRNA m6A levels. Knockdown of FTO increased the expression of GABAAR protein and GABAAα2 mRNA m6A levels. Data from rat models further demonstrate that inhibition of FTO suppressed GABAAR protein expression in the hypothalamus, causing delayed puberty onset. Collectively, our findings suggest that FTO-dependent m6A demethylation plays a critical role in regulating GABAAR mRNA processing in GnRH neurons.

The Role of PTEN/PI3K/AKT Signaling Pathway in Apoptosis of Liver Cells in Cocks with Manganese Toxicity.

PTEN/PI3K/AKT signaling pathway is an important pathway for cell proliferation and apoptosis. Exposure to excess manganese (Mn) can cause damage in organisms. However, whether Mn toxicity can cause apoptosis is still not clear. In order to explore the mechanism of PTEN/PI3K/AKT signaling pathway responsible for Mn-induced apoptotic injury, 160 Hyline cocks were divided into four groups; there were the control group (Con group), the low-dose Mn group (L group), the medium-dose Mn group (M group), and the high-dose Mn group (H group). The cocks in Con group, L group, M group, and H group were fed with MnCl2 diet containing 100, 600, 900, and 1800mg/kg, respectively. The growth status of cocks in each group was observed on days 30, 60, and 90. Thirty cocks were randomly selected from each group and sacrificed on day 90 for optical microscope observation and fluorescence microscopic observation, as well as for transcription-level expression of apoptosis-related genes and heat shock proteins (HSPs) in the liver. The results showed that the growth status of cocks was gradually depressed with the extension of feeding time and with the increase of Mn dose. On day 90, the results of optical microscope observation and fluorescence microscope observation showed that damage and apoptosis appeared in the cock liver cells under Mn exposure groups. The results of transcription-level detection of apoptosis-related genes and HSPs indicated that Mn exposure upregulated eleven pro-apoptotic genes (including RIP1, RIP3, MLKL, Bax, Caspase-3, FADD, Cyt-C, ERK, JNK, Caspase-8, and P38) and downregulated one anti-apoptotic gene Bcl-2, further meaning that exposure to Mn-induced apoptosis in cock liver cells and PTEN/PI3K/AKT signaling pathway took part in molecular mechanism of apoptosis caused by excess Mn. Moreover, in our experiment, the increase of four HSPs (including HSP27, HSP40, HSP60, and HSP70) was found after Mn treatment for 90days, which indicated that Mn stress triggered HSPs and HSPs were involved in molecular mechanism of Mn poisoning in cock livers. In addition, we also found there was upregulated dose-dependent manner in fifteen detected genes and there was downregulated dose-dependent manner in Bcl-2, indicating that the apoptosis caused by Mn poisoning in cock liver cells was dose-dependent.

Assessing fine fescue mixtures and plant growth regulator applications to determine their effect on traffic tolerance and divot recovery

AbstractThere has been some transition to using low‐input fine fescues on golf courses, but these species have poor traffic tolerance and divot recovery, making them impractical for playable areas on golf courses. The objectives of this study were to determine the effect of the plant growth regulator (PGR) trinexapac‐ethyl on the performance of fine fescue mixtures when managed as a golf course fairway and to identify fine fescue mixtures that perform well under traffic stress. Twenty‐five mixtures were tested that combined ‘Treazure II’ chewings fescue (Festuca rubra L. ssp. commutata Gaudin), ‘Beacon’ hard fescue (Festuca brevipila Tracey), ‘Navigator II’ strong creeping red fescue (Festuca rubra L. ssp. rubra Gaudin), ‘Shoreline’ slender creeping red fescue [Festuca rubra L. ssp. littoralis (G. Mey.) Auquier], and ‘Quatro’ sheep fescue (Festuca ovina L.). Field experiments were conducted in St. Paul, MN, with PGR, mixture, and traffic treatments. The benefits of the PGR trinexapac‐ethyl on fine fescue fairway quality was relatively small compared with the benefits of traffic management and mixture selection. Hard fescue, slender creeping red fescue, strong creeping red fescue, and sheep fescue had the greatest impact on increasing visual turfgrass quality after traffic treatments. There was no significant difference in divot recovery with any mixtures, and no divots had recovered after 12 mo.

Manganese exposure causes movement deficit and changes in the protein profile of the external globus pallidus in Sprague Dawley rats

Manganese (Mn) is required for normal brain development and function. Excess Mn may trigger a parkinsonian movement disorder but the underlying mechanisms are incompletely understood. We explored changes in the brain proteomic profile and movement behavior of adult Sprague Dawley (SD) rats systemically treated with or without 1.0 mg/mL MnCl2 for 3 months. Mn treatment significantly increased the concentration of protein-bound Mn in the external globus pallidus (GP), as demonstrated by inductively coupled plasma mass spectrometry. Behavioral study showed that Mn treatment induced movement deficits, especially of skilled movement. Proteome analysis by two-dimensional fluorescence difference gel electrophoresis coupled with mass spectrometry revealed 13 differentially expressed proteins in the GP of Mn-treated versus Mn-untreated SD rats. The differentially expressed proteins were mostly involved in glycolysis, metabolic pathways, and response to hypoxia. Selected pathway class analysis of differentially expressed GP proteins, which included phosphoglycerate mutase 1 (PGAM1), primarily identified enrichment in glycolytic process and innate immune response. In conclusion, perturbation of brain energy production and innate immune response, in which PGAM1 has key roles, may contribute to the movement disorder associated with Mn neurotoxicity.

Long-term organic substitution management affects soil phosphorus speciation and reduces leaching in greenhouse vegetable production

Excessive phosphorus (P) fertilizer and manure application is widespread in greenhouse vegetable production, causing P accumulation and groundwater pollution. The partial substitution of chemical fertilizer with organic amendments may effectively address this problem; however, little is known about P speciation and transformation at the molecular scale. Here, we combined P K-edge X-ray absorption near-edge structure, 31P nuclear magnetic resonance spectroscopy, and chemical extraction to characterize P speciation and assess P leaching in a 10-year field experiment including chemical fertilizer (4CN) and replacement of half the chemical N fertilizer with manure (2CN+2 MN), straw (2CN+2SN), or combined manure and straw (2CN+1 MN+1SN) treatments. Compared to the 4CN treatment, organic substitution treatments resulted in 10.0–16.3% lower P accumulation and 57.3–102% higher organic P. Newberyite was detected in the organic substitution treatments, making up 6.9–13.0% of the total P, and the hydroxyapatite proportion was 7.3–15.6% lower than that in the 4CN treatment. Moreover, 2CN+2 MN treatment increased the orthophosphate diester content and labile P (Resin-P and NaHCO3–P) proportion, and 2CN+2SN treatment increased the orthophosphate monoester content and moderately labile P (NaOH–P) proportion. The 2CN+1 MN+1SN treatment exhibited the advantages of both manure and straw application. Partial least squares path modeling revealed that labile P was affected mainly by manure application and pH, and moderately labile P was influenced mainly by straw application and alkaline phosphomonoesterase activity. Compared with the 4CN treatment, the organic substitution treatments significantly decreased the total P leaching losses by 21.3–48.8%. Our results provide new insights into soil P transformation in response to different organic amendments. Combined manure, straw, and chemical fertilizer application (2CN+1 MN+1SN treatment) was a more effective practice for developing sustainable P management practices by comprehensively considering soil P transformation, vegetable yields, and environmental losses.

Manganese accumulation and tissue-level distribution in Australian Macadamia (Proteaceae) species

Background and aimsAustralian Macadamia species are known for their edible nuts as well as their ability to take up high concentrations of manganese (Mn) into their leaves. However, little is known about the ecophysiology of Mn in species of Macadamia. MethodsThis study investigated (i) Mn accumulation in wild Macadamia using handheld X-ray fluorescence spectroscopy (XRF) of herbarium collections, and (ii) Mn uptake in three out of four known Macadamia species (M. tetraphylla, M. integrifolia and M. ternifolia) in a pot experiment that delivered Mn treatments in both solid (as natural Mn-minerals mixed with quartz sand) and liquid form (as MnSO4 solution added to soil). Tissue samples were analysed for bulk elemental concentrations and for in vivo distribution of Mn and other elements using laboratory μXRF analysis. Key resultsThe results revealed that wild M. ternifolia and M. integrifolia are strong Mn accumulators with up to 9600 μg Mn g−1 and 8500 μg Mn g-1, respectively, followed by M. jansenii (6400 μg Mn g-1) and M. tetraphylla (5100 μg Mn g-1). Under the controlled conditions, high Mn accumulation was demonstrated for M. integrifolia and M. tetraphylla with greater than 7500 μg Mn g−1 in mature leaves in the highest Mn treatment level. Our results further showed that Mn was efficiently translocated from the roots to the shoots with translocation factor >1 in the studied species. The laboratory μXRF analysis revealed that Mn was absent from the vascular bundles and concentrated in the areas between veins. ConclusionsAll the four Macadamia species have high foliar Mn concentrations qualifying them as strong Mn accumulators in nature as determined by handheld XRF analysis of herbarium specimens. Under experimental conditions, M. integrifolia and M. tetraphylla were confirmed to be strong Mn accumulators. Manganese was shown by laboratory μXRF analysis to be concentrated in the inter-veinal areas of the leaf lamina.

Heat shock proteins took part in oxidative stress-mediated inflammatory injury via NF-κB pathway in excess manganese-treated chicken livers

Manganese (Mn) is an essential metal in humans and animals. However, excess Mn entered environment due to the wide application of Mn in industry and agriculture, and became an environmental pollutant. Exposure to high doses of Mn is toxic to humans and animals (including chickens). Liver is a target organ of Mn poisoning. Nevertheless, there were few studies on whether Mn poisoning damages chicken livers and poisoning mechanism of Mn in chicken livers. Herein, the aim of this study was to explore if oxidative stress, heat shock proteins (HSPs), and inflammatory response were involved in the mechanism of Mn poisoning-caused damage in chicken livers. A chicken Mn poisoning model was established. One hundred and eighty chickens were randomly divided into one control group (containing 127.88 mg Mn kg−1) and three Mn-treated groups (containing 600, 900, and 1800 mg Mn kg−1, respectively). Histomorphological structure was observed via microstructure and ultrastructure. Spectrophotometry was used to detect total antioxidant capacity (T-AOC) and inducible nitric oxide synthase (iNOS) activity, as well as nitric oxide (NO) content. And qRT-PCR was performed to measure mRNA expression of inflammatory genes (nuclear factor kappa B (NF-κB), tumor necrosis factor α (TNF-α), cyclooxygenase-2 (COX-2), prostaglandin E2 (PGE2), and iNOS) and heat shock protein (HSP) genes (HSP27, HSP40, HSP60, HSP70, and HSP90). Multivariate correlation analysis, principal component analysis, and cluster analysis were used to demonstrate the reliability of mechanism of Mn poisoning in our experiment. The results indicated that excess Mn led to inflammatory injury at three contents and three time points. Meanwhile, we found that NO content, iNOS activity, and NF-κB, TNF-α, COX-2, PGE2, and iNOS mRNA expression increased after Mn treatment, meaning that exposure to Mn induced inflammatory response via NF-κB pathway in chicken livers. Moreover, excess Mn decreased T-AOC activity, indicating that Mn exposure caused oxidative stress. Furthermore, mRNA expression of above five HSP genes was up-regulated during Mn exposure. Oxidative stress triggered the increase of HSPs and the increase of HSPs mediated inflammatory response induced by Mn. In addition, there were time- and dose-dependent effects on Mn-caused chicken liver inflammatory injury. Taken together, HSPs participated in oxidative stress-mediated inflammatory damage caused by excess Mn in chicken livers via NF-κB pathway. For the first time, we found that oxidative stress can trigger HSP70 and HSPs can trigger poisoning-caused inflammatory damage, which needs to be further explored. This study provided a new insight into environmental pollutants and a reference for further study on molecular mechanisms of poisoning.

Removal of Mn via coprecipitation and sorption by Fe(II), Fe(III), and Al in mine drainage

In mine drainage, Fe and Mn are the two most abundant elements exceeding the discharge criteria. Although Mn removal generally requires a pH exceeding 9.5–10.0, its coprecipitation and sorption by Fe and/or Al can significantly reduce the required pH. In this study, Mn removal efficiencies, mechanisms, and required pH were investigated by experiments involving varying concentrations of Mn, Fe, and Al at different pH, and X-ray photoelectron spectroscopy (XPS) analyses. At pH > 7.9, precipitation as Mn (hydr)oxides was the principal Mn removal process, as indicated by the Mn removal plots, geochemical modeling, and XPS results. The precipitation was highly promoted by the heterogeneous oxidation of Fe and Al hydroxides. Coprecipitation-sorption experiments showed 65–80% lower Mn concentrations than those of sorption experiments at similar dosages and pH near 7.5. Fe(III) exhibited higher coprecipitation efficiency than Fe(II), possibly due to the prior oxidation of Fe(II). Fe(III) also displayed a coprecipitation-sorption efficiency five times more than Al. To decrease the Mn concentrations from 17–25 mg L−1 to <2 mg L−1 by coprecipitation-sorption, Fe(III)/Mn and Fe(II)/Mn ratios of ∼10 and ∼20, respectively, at pH 9.0 were required. Similarly, an Al/Mn ratio of ∼7 at pH 9.0 was required to reduce the Mn concentration to <5 mg L−1. Furthermore, the required Fe/Mn ratio decreased significantly when the initial Mn concentration decreased to 8–11 mg L−1. Utilizing the deduced relationships, required pH for Mn removal could be estimated and the design of Mn treatment facilities can be more efficient.

YAC128 mouse model of Huntington disease is protected against subtle chronic manganese (Mn)-induced behavioral and neuropathological changes

Manganese (Mn) is an essential micronutrient but excessive levels induce neurotoxic effects. Increasing evidence suggests a deficit of bioavailable Mn in Huntington disease (HD), an inherited neurodegenerative disease characterized by motor and cognitive disturbances. Previous studies have shown rescue of some molecular HD phenotypes by acute Mn exposure. This study simultaneously examined the potential for chronic Mn exposure to attenuate HD behavioral phenotypes, and for the HD genotype to offer protection against detrimental effects of chronic Mn exposure. In two independent studies a chronic Mn exposure paradigm was implemented in the YAC128 mouse model of HD and behavior was assessed at several timepoints. Study 1 exposed WT and YAC128 mice to twice weekly subcutaneous injections of 0, 5, 15, or 50 mg/kg MnCl[2] tetrahydrate from 12 to 32 weeks of age. A promising protective effect against motor coordination decline in 5 mg/kg MnCl[2] tetrahydrate-treated YAC128 mice was detected. Study 2 thus exposed WT and YAC128 mice to either 0 or 5 mg/kg MnCl[2] tetrahydrate from 12 to 52 weeks of age (with a partial randomized treatment crossover at 31 weeks). The same protective effect was not observed under these conditions at higher statistical power. We report subtle toxicological changes in exploratory behavior and total activity induced by chronic Mn exposure in WT mice only, despite similar total increases in brain Mn in WT and YAC128 mice. Further, chronic Mn treatment resulted in a 10–12 % decrease in striatal NeuN positive cell density in WT mice but not YAC128 mice, despite vehicle cell counts already being reduced compared to WT mice as expected for the HD genotype. The subtle changes observed in specific outcome measures, but not others, following long-term low-level Mn exposure in WT mice delineate the neurobehavioral and neuropathological effects at the threshold of chronic Mn toxicity. We conclude that these chronic low-dose Mn exposures do not significantly rescue behavioral HD phenotypes, but YAC2128 mice are protected against the subtle Mn-induced behavioral changes and decreased striatal neuron density observed in Mn-exposed WT mice.

Manganese promoted wheat straw decomposition by regulating microbial communities and enzyme activities

This study investigated the dose-effect of manganese (Mn) addition on wheat straw (WS) decomposition, and explored the potential mechanisms of Mn involved in the acceleration of WS decomposition in regards to the soil microbial communities and enzyme activities. A 180-day incubation experiment was performed to examine the decomposition of WS under four Mn levels, that is, 0, 0.25, 1 and 2mgg-1 . The effects of microbial communities and enzyme activities were evaluated using control (0mgg-1 ) and Mn (0.25mgg-1 ) treatments. Our results revealed that Mn (0.25mgg-1 ) addition significantly increased WS decomposition, and enhanced the release of carbon and nitrogen. Optimal Mn addition (0.25mgg-1 ) also caused significant increases in the activity of neutral xylanase (NEX), laccase (Lac), manganese peroxidase (MnP) and lignin peroxidase (LiP) within the incubation period. Mn (0.25mgg-1 ) addition also enriched some operational taxonomic units (OTUs) that, in turn, had the potential ability to decompose crop straw, such as secreting lignocellulolytic enzymes. Mn (0.25mgg-1 ) could promote WS decomposition through enrichment of the microbial species involved in biomass decomposition, which enhanced the lignocellulose-degrading enzyme activity. This study provides evidence for Mn to promote WS biodegradation after Mn application, opening new windows to improve the utilization efficiency of crop residues.

Biophenolic Profile Modulations in Olive Tissues as Affected by Manganese Nutrition.

Manganese (Mn) is an essential element that intervenes in several plant metabolic processes. The olive tree, and its fruits and leaves, are known as a source of nutraceuticals since they are rich in biophenols. However, there is still a serious lack of data about biophenolic distribution in olive stems and roots under Mn fertilisation. In this context, our study aimed to examine the effects of Mn fertilisation on the biophenolic profile in the leaves, stems, and roots of the ‘Istarska bjelica’ olive cultivar. The experiment was set up in a greenhouse, during a period of five months, as a random block design consisting of three treatments with varying Mn concentrations in full-strength Hoagland’s nutrient solution (0.2 µM Mn, 12 µM Mn, and 24 µM Mn). The obtained results indicate that the amount of Mn in the examined olive plant tissues was significantly higher under 12 µM Mn and 24 µM Mn treatments compared to that of the 0.2 µM Mn treatment. While the concentration of biophenols varied in roots depending on the compound in question, a strong positive impact of the increased Mn concentration in nutrient solution (12 µM Mn and 24 µM Mn) on the concentrations of the main biophenolic compounds was observed in stems. The concentration of oleuropein in leaves almost doubled at 24 µM Mn, with the highest Mn concentration, as compared to the 0.2 µM Mn treatment. The obtained results led to the conclusion that the supply of Mn could enhance the concentration of some biologically active compounds in olives grown hydroponically, implying a critical need for further investigation of Mn fertilisation practices in the conventional olive farming system.

Manganese Mitigates Heat Stress–Induced Apoptosis by Alleviating Endoplasmic Reticulum Stress and Activating the NRF2/SOD2 Pathway in Primary Chick Embryonic Myocardial Cells

Heat stress leads to oxidative stress and induces apoptosis in various cells. Endoplasmic reticulum (ER) stress is an important apoptosis pathway. Manganese (Mn) has been shown to enhance the activity of manganese superoxide dismutase (MnSOD). To explore the potential effect of Mn on ER stress and apoptosis induced by heat stress, we examined crucial factors associated with heat stress, ER stress, and apoptosis in cultured primary chick embryonic myocardial cells that had been pretreated with 20μM Mn for 24h and then subjected to 4h of heat stress. The results showed that Mn decreased (P < 0.05) heat stress-induced reactive oxygen species (ROS) production and exerted antiapoptotic effects by increasing MnSOD enzymatic activity. The heat stress-induced accumulation of intracellular calcium was dramatically reduced (P < 0.05). Mn treatment significantly decreased (P < 0.05) the expression levels of the apoptosis-related gene Bax and ER stress markers glucose-regulated protein 78 (GRP78) and CCAAT/enhancer binding protein homologous protein (CHOP) in primary chick embryonic myocardial cells. Additionally, Mn reduced oxidative stress by activating the nuclear factor E2-related factor 2 (NRF2)/SOD2 signaling pathway. Taken together, our findings indicate that Mn attenuates heat stress-induced apoptosis by inhibiting ROS generation, intracellular calcium accumulation, and the ER stress pathway and activating the NRF2/SOD2 signaling pathway to protect myocardial cells from oxidative stress during chick embryonic development.

Manganese uptake by red maples in response to mineral dissolution rates in soil

Manganese (Mn) is an essential plant micronutrient that influences photosynthesis, ecosystem productivity, and soil carbon storage. Our objective was to quantify how Mn uptake by forest vegetation relates to Mn release into soil solution through mineral dissolution. A greenhouse pot experiment was conducted to quantify Mn uptake by red maple saplings as a function of mineral solubility to test whether Mn uptake was limited by the supply of Mn to soil solution. Differences in soil microbial community composition between treatments, particularly amongst Mn cycling bacteria and fungi, were also evaluated to assess potential microbial impacts on observed Mn fluxes. Plant Mn uptake was highest in systems supplied with dissolved Mn(II) because it was not kinetically limited by mineral weathering. Mn uptake was also higher in systems supplied with a fast-weathering substrate (shale containing Mn(II)-bearing pyrite) than a slow-weathering substrate (Mn(IV)-oxide). However, vegetation accumulated a decreasing proportion of available Mn with increasing solubility, indicating that uptake was tempered relative to solubility. The presence of bacterial phyla containing known Mn-oxidizing bacteria indicates the potential for Mn-oxidizing bacteria to influence Mn solubility within Mn-oxide and dissolved Mn treatments. A relatively low abundance of these bacteria points to their limited capacity to oxidize and retain Mn in the shale treatments, consistent with substantial Mn leaching. We conclude that Mn uptake was primarily controlled by dissolution rates of Mn-bearing minerals but modified by biological processes. The quantitative framework presented here can guide understanding of how biogeochemical processes control element cycling between plants and soils.

Co–application effect of herbicides and micronutrients on weeds and nutrient uptake in flooded irrigated rice: Does it have a synergistic or an antagonistic effect?

In submersed rice fields, weeds are considered the main source of nutrients removal. Hence, reduction in yield and grain quality is realized. Thus, a two–year field experiment was performed to find out the best cooperative effect between herbicides and micronutrients for controlling rice weeds with yield in mind. Two herbicides (halosulfuron–methyl and bentazone) and three micronutrients (Fe, Mn and Zn) were arranged in a strip plot design with three replicates. Results exhibited that in plots treated by halosulfuron–methyl, the control treatment (without fertilizing) showed the maximum reductions in weed N, P and K uptake, however, it statistically equaled Fe and Mn treatments in weed N uptake and Mn, Fe and Zn treatments in weed K uptake. With controlling weeds by halosulfuron–methyl herbicide, Zn treatment was as similar as Fe and Mn treatments for increasing plant height, straw yield and grain yield of rice. The interactions of halosulfuron–methyl x Zn treatment (for N and P in rice grain) and halosulfuron–methyl x Zn or Fe treatments (for P in rice grain) had synergistic effects. Moreover, the highest increases in Fe, Mn and Zn contents in rice grains were recorded with halosulfuron–methyl plus Fe, Mn and Zn treatments, respectively. In conclusion, rice producers should be aware of the synergism and co–operative effects between herbicides and micronutrients. The synergistic effect could be exploited for reducing the hazardous impacts of weeds, and hence, it raises yield potentiality and quality.

Can foliar-applied nutrients improve caraway (Carum carvi L.) seed oil composition?

Caraway seeds contain between 0.5–7% essential oil, rich in monoterpenes that have a characteristic aroma and chemical properties. Caraway oil has several bioactive compounds that are of industrial importance, particularly for pharmaceutical and health care products. Carvone and limonene are the main terpenes present in caraway oil, which along with some unique fatty acids (i.e. petroselinic acid) determine caraway (Carum carvi L.) oil quality. Both terpenes are important raw materials for industrial applications and their concentration influences the price of caraway seed and oil, hence there is need for identifying management practices that may increase the concentration of these and other bioactive compounds to improve caraway seed oil quality. A field experiment with five treatments: a control and a series of foliar-applied micronutrients (either Cu, Mg, Mn or Zn was done to identify their potential to enhance caraway oil quality. Solid-phase microextraction and gas chromatography with a flame ionization detector were used to characterize oil quality. Our results indicate that while the micronutrient treatments have a significant effect on essential oil composition, both in carvone and limonene, such an effect was not found on all fatty acids but only in two of them—palmitoleic and vaccenic acid—, which were highest after the Mn treatment. Overall, the carvone content of the seeds decreased the least between years following Mn treatment. Mn treatment also caused an increase in limonene in the second year in contrast to the trend for all other treatments. The Mn foliar spray needs to be studied further to elucidate whether it could have a consistent positive effect on caraway oil seed quality upon adjusting dosage and spraying time.

Effects of manganese on microglia M1/M2 polarization and SIRT1‐mediated transcription of STAT3‐dependent genes in mouse

Overexposure to manganese (Mn) can lead to neurological diseases, characterized by behavioral and motor impairments. Microglia-mediated neuroinflammation is involved in the pathogenesis and progression of neurodegenerative diseases. Microglial M1 and M2 phenotypes play pro-inflammatory and anti-inflammatory roles, respectively, in response to microenvironmental disturbances. Silent information regulator (SIRT1) has been demonstrated to play an important role in the neuroinflammatory response by deacetylating various transcription factors, such as proliferator-activated receptor γ coactivator 1α (PGC-1α), nuclear factor kappa B (NF-κB), and signal transducer and activator of transcription 3 (STAT3). In addition, PGC-1α and STAT3 have been implicated in microglial polarization and inflammatory response. In this study, Mn exposure (50, 100, 200μmol/kg) induced neuroinflammatory injury and interfered with microglial M1/M2 polarization in mice, as indicated by the upregulated expression of M1 polarization marker mRNA (IL-1β, IL-6, TNF-α, and iNOS), whereas changes in M2 polarization markers (IL-4, TGF-β, and Arg1) varied, with some increasing and some decreasing, in response to increasing Mn doses, which was consistent with the flow cytometry results used to detect the percentages of each microglial type. We found that Mn could downregulate SIRT1 expression and activate NF-κB signaling. Following mice in the 200 μmol/kg Mn treatment, STAT3 and PGC-1α levels in the nuclear fraction both significantly decreased, and the interaction between the proteins decreased, affecting the transcription of STAT3-mediated genes. These findings provide new insights regarding the role played by Mn neurotoxicity in the suppression of neuroinflammation through the regulation of microglial polarization.