Academic literature on the topic 'Mn toxicity'

Greenhouse studies were conducted to evaluate 5 levels of Mn (0.00025 to 0.1 g.L-1) on Mn toxicity or tolerance of sweetpotato [Ipomoea batatas (L.) Lam] grown in a modified half Hoagland's solution. The presence of oxidized Mn on the roots and leaves was demonstrated by the blue staining test with benzidene and the solubility and bleaching of oxidized Mn in the oxalic-sulfuric acid solution. Both storage root and foliage fresh and dry weights were highest at Mn concn of 0.00025 g.L-1 in the nutrient solution, while fibrous root dry weight was highest with 0.01 g.L-1 Mn in the solution. More Mn accumulated in foliage than in fibrous roots for all levels of Mn evaluated. N, P, and K concn in foliage was highest at a Mn concn of 0.1 g.L-1 Mn in the solution. Foliage dry weight was preserved up to a high Mn level of about 2700 ug. g-1 Mn in tissues, while taht for storage roots was preserved up to a high Mn level of about 1000 ug. g-1 in the tissues. Deposition of oxidized Mn was observed on fibrous roots particularly at the highest Mn levels in the nutrient solution.

Abstract Muskmelons (Cucumis melo L.) ‘Harvest Queen’ were grown in sand culture to evaluate the response to Mn toxicity as affected by solution concentration of Mn and Mg. Manganese toxicity symptoms were developed as water-soaked spots, necrotic spots, and necrotic lesions, which were most severe on the lower mature leaves. Leaves developed toxicity symptoms when they contained ≥900 μ-g·g-1 Mn. Increased levels of Mg in the nutrient solution alleviated symptoms of Mn toxicity, decreased Mn concentration in shoot and root tissues, and increased growth of muskmelon plants. The reduction in Mn toxicity was brought about by reduced root absorption of Mn at high Mg supply.

The effects of 0.25, 1.0, 2.5, 10, and 100 mg Mn/liter on sweetpotato [Ipomoea batatas (L.) Lam] were evaluated in a greenhouse during 2 years using the nutrient film technique. Foliage and storage root dry weights declined linearly as Mn concentration increased in either whole plants or fibrous roots. Foliage and storage root dry weights were equally sensitive to Mn concentration in whole plants but 5 to 15 times more sensitive to increased Mn concentration in the fibrous roots. Foliar N, P, K, Ca, and Mg concentrations were adequate and did not appear to limit plant growth. Manganese concentrations in solution had very little effect on Fe, Zn, or B concentration. Manganese concentration was higher in the foliage than in fibrous roots. Plant roots showed browning at the higher (10 or 100 mg Mn/liter) concentrations in solution, which indicated the presence of oxidized Mn. Characteristic toxicity symptoms were observed in plants receiving 2.5 (moderate), 10, or 100 mg Mn/liter in solution.

Abstract Muskmelon (Cucumis melo L.) ‘Harvest Queen’ seedlings were grown in sand culture at 2, 15, or 30 ppm Mn with 3 different N treatments to evaluate the effects of N form on growth, composition, and development of Mn toxicity. Nitrogen treatments consisted of NO3, NH4, and NH4 shifted to NO3 at 5 days, when Mn toxicity symptoms began to show on NO3-treated plants. Muskmelons produced the most growth with N supplied as NO3, least growth with NH4, and intermediate growth with the NH4-to-NO3 shift treatment. Plants grown with NO3-N at 15 or 30 ppm of Mn had restricted growth, developed Mn toxicity symptoms 5 days after the start of Mn treatments, and had a Mn composition of over 1500 ppm in dry shoot tissue. With NH4 the Mn treatments had no effect on growth, no Mn toxicity symptoms developed, and Mn composition of shoot tissue was <800 ppm. Shifting plants from NH4 to NO3-N resulted in the development of Mn toxicity symptoms and tissue Mn composition over 1500 ppm within 4 days after the shift.

Abstract Watermelon [Citrullus lanatus (Thunb.)] ‘Sugar Baby’ seedlings were grown in sand culture leached with nutrient solution containing 2, 25, or 50 mg·liter−1 Mn in combination with NH4 or NO3-N to evaluate the effects of N form on growth, composition, and development of Mn toxicity. Nitrogen form treatments consisted of continuous NO3, continuous NH4, and a treatment in which NH4 was replaced by NO3 after Mn toxicity symptoms were first observed on NO3-treated plants. Watermelon plants produced the most growth at all Mn levels with N supplied as NO3, least with NH4, and intermediate with the NH4-to-NO3 shift treatment. Plants grown with NO3-N at 25 and 50 mg·liter−1 Mn had reduced growth and developed Mn toxicity symptoms with Mn concentrations >1700 μg·g−1 in shoot tissues. However, with NH4 the Mn treatments had no effect on growth, no Mn toxicity symptoms developed, and Mn concentrations in shoot tissue were <800 μg·g−1. Shifting plants from NH4-to-NO3 nutrition at 50 mg·liter−1 Mn in solution stimulated rapid Mn absorption and produced Mn toxicity symptoms within 3 days.

Manganese (Mn) is an important micronutrient for growth and development in plants, however, excess Mn is harmful by disrupting photosynthesis system and inducing oxidative damage in leaves. MicroRNAs (miRNAs) play key roles in regulating Mn toxicity tolerance in plants. Here, we identified Mn toxicity-responsive miRNAs in Arabidopsis by using small RNA sequencing. Eighteen differentially expressed miRNAs were identified in Arabidopsis thaliana seedlings in response to Mn toxicity. These differentially expressed miRNAs are involved in regulating nutrition homeostasis, transport, stress response, and developmental processes. Our results indicated that these miRNAs play a key role in Mn toxicity response in plants.

The interaction of manganese with cadmium (Cd) toxicity was studied on maize plants grown in hydroponics. Manganese supplied as MnSO₄clearly alleviated the toxic effect of cadmium on the root growth of maize seedlings. The magnitude of alleviation was dose dependant and total abolition of 10&micro;M Cd toxicity on root growth was observed at Mn/Cd ratio of 20:1. The 12 h pre-treatment with 10&mu;M Cd was generally toxic for nitrate uptake and reduction (both determined in Cd-free media). The beneficial effect of 100&mu;M Mn on this toxicity was confirmed for the low-affinity nitrate uptake system, but on the other hand, Mn alone seems to be slightly toxic for high affinity nitrate uptake system and on the nitrate reductase activity.

Excess Manganese (Mn) is toxic to plants and reduces crop production. Although physiological and molecular pathways may drive plant responses to Mn toxicity, few studies have evaluated Mn tolerance capacity in roots and leaves. As a result, the processes behind Mn tolerance in various plant tissue or organ are unclear. The reactivity of peanut (Arachis hypogaea) to Mn toxicity stress was examined in this study. Mn oxidation spots developed on peanut leaves, and the root growth was inhibited under Mn toxicity stress. The physiological results revealed that under Mn toxicity stress, the activities of antioxidases and the content of proline in roots and leaves were greatly elevated, whereas the content of soluble protein decreased. In addition, manganese and iron ion content in roots and leaves increased significantly, but magnesium ion content decreased drastically. The differentially expressed genes (DEGs) in peanut roots and leaves in response to Mn toxicity were subsequently identified using genome-wide transcriptome analysis. Transcriptomic profiling results showed that 731 and 4589 DEGs were discovered individually in roots and leaves, respectively. Furthermore, only 310 DEGs were frequently adjusted and controlled in peanut roots and leaves, indicating peanut roots and leaves exhibited various toxicity responses to Mn. The results of qRT-PCR suggested that the gene expression of many DEGs in roots and leaves was inconsistent, indicating a more complex regulation of DEGs. Therefore, different regulatory mechanisms are present in peanut roots and leaves in response to Mn toxicity stress. The findings of this study can serve as a starting point for further research into the molecular mechanism of important functional genes in peanut roots and leaves that regulate peanut tolerance to Mn poisoning.

Although manganese (Mn) is an essential trace element, overexposure is associated with Mn-induced toxicity and neurological dysfunction. Even though Mn-induced oxidative stress is discussed extensively, neither the underlying mechanisms of the potential consequences of Mn-induced oxidative stress on DNA damage and DNA repair, nor the possibly resulting toxicity are characterized yet. In this study, we use the model organism Caenorhabditis elegans to investigate the mode of action of Mn toxicity, focusing on genomic integrity by means of DNA damage and DNA damage response. Experiments were conducted to analyze Mn bioavailability, lethality, and induction of DNA damage. Different deletion mutant strains were then used to investigate the role of base excision repair (BER) and dePARylation (DNA damage response) proteins in Mn-induced toxicity. The results indicate a dose- and time-dependent uptake of Mn, resulting in increased lethality. Excessive exposure to Mn decreases genomic integrity and activates BER. Altogether, this study characterizes the consequences of Mn exposure on genomic integrity and therefore broadens the molecular understanding of pathways underlying Mn-induced toxicity. Additionally, studying the basal poly(ADP-ribosylation) (PARylation) of worms lacking poly(ADP-ribose) glycohydrolase (PARG) parg-1 or parg-2 (two orthologue of PARG), indicates that parg-1 accounts for most of the glycohydrolase activity in worms.

Manganese (Mn) is an essential element for plant growth due to its participation in a series of physiological and metabolic processes. Mn is also considered a heavy metal that causes phytotoxicity when present in excess, disrupting photosynthesis and enzyme activity in plants. Thus, Mn toxicity is a major constraint limiting plant growth and production, especially in acid soils. To cope with Mn toxicity, plants have evolved a wide range of adaptive strategies to improve their growth under this stress. Mn tolerance mechanisms include activation of the antioxidant system, regulation of Mn uptake and homeostasis, and compartmentalization of Mn into subcellular compartments (e.g., vacuoles, endoplasmic reticulum, Golgi apparatus, and cell walls). In this regard, numerous genes are involved in specific pathways controlling Mn detoxification. Here, we summarize the recent advances in the mechanisms of Mn toxicity tolerance in plants and highlight the roles of genes responsible for Mn uptake, translocation, and distribution, contributing to Mn detoxification. We hope this review will provide a comprehensive understanding of the adaptive strategies of plants to Mn toxicity through gene regulation, which will aid in breeding crop varieties with Mn tolerance via genetic improvement approaches, enhancing the yield and quality of crops.

O manganês é um elemento traço essencial, porém existe uma preocupação com seus potenciais efeitos neurotóxicos associados à exposição a níveis excessivos, podendo provocar uma síndrome conhecida como manganismo, cujos sintomas são semelhantes aos da doença de Parkinson. A maioria dos trabalhos envolvendo manganês usa espécies de Mn(II), mas sabe-se que Mn(III) é acumulado em maior quantidade no cérebro. Nesse sentido, foi feito um estudo dos danos oxidativos e de toxicidade provocados por três complexos de Mn(III): citrato, pirofosfato e salicilenodiamina (respectivamente MnCit, MnPPi e EUK8). Para tanto, as três espécies foram sintetizadas e caracterizadas por métodos espectroscópicos. Em seguida foram determinadas suas capacidades pró-oxidantes sobre os seguintes marcadores: dihidrorodamina (DHR), tirosina (Tyr), albumina (BSA) e dopamina (DA). Finalmente, seu efeito sobre células cerebelares e da cepa HeLa estressada por meio de irradiação UV também foi avaliado, e foi usado ascorbato na tentativa de tratar o dano sobre células HeLa. O teste com a DHR também foi feito em presença de H2O2 e ascorbato. A capacidade pró-oxidante testada por fluorescência da DHR sugere que o ascorbato atua como anti-oxidante. Além disso, MnCit e MnPPi (mas não EUK8), quando na presença de H2O2, são menos oxidantes. O mesmo comportamento foi percebido nas medidas de fluorescência de Tyr. A carbonilação da BSA, verificada pela absorbância do seu marcador (DNPH), seria indício de capacidade oxidante dos complexos, mas não percebeu-se variação significativa de grupos C=O na proteína após tratamento com espécies de Mn(III), mesmo em amostras com H2O2, embora notem-se as mesmas tendências apresentadas pelos complexos com DHR e Tyr. Estudos de oxidação de DA por luminescência tiveram resultados inconclusivos, mas dados mais concretos em testes com medidas de absorbância de soluções de DA e fluorescência de misturas de DA com DHR indicaram que DA é preferencialmente oxidada por todos os compostos. A viabilidade celular de culturas de células neuronais granulares (CGC) mostrou pouca diferença entre as toxicidades dos compostos, mas verifica-se uma relação inversamente proporcional entre as toxicidades e lipofilicidades dos complexos. O mesmo não ocorre nos experimentos com HeLa, cuja viabilidade foi avaliada por contagem de colônias após fixação e coloração das células, pois nesse caso o EUK8 se mostrou o mais tóxico dos três. Além disso, ao contrário do observado com a DHR, o ascorbato teve ação pró-oxidante, e, aparentemente, houve um efeito sinérgico negativo entre os complexos e a radiação UV. Tratamento com o quelante p-aminossalicilato só foi eficaz na recuperação das culturas para amostras não irradiadas.
Manganese is an essential trace element, however there is considerable concern regarding its neurological effects when in excess, giving rise to a condition termed manganism which is characterized by Parkinson disease-like symptoms. Most evaluations of manganese toxicity use poorly defined Mn(II) species, although Mn(III) is known to accumulate preferentially in the brain. Therefore, in this work we proposed a study of oxidative damage and citotoxicity of Mn(III) derivatives of citrate, pyrophosphate and salycilenediamine (respectively, MnCit, MnPPi and EUK8). The species were synthesized and characterized by spectroscopic methods. Their pro-oxidant abilities were assessed over markers of oxidant activity dihydrorhodamine (DHR), tyrosine (Tyr), albumin (BSA) and dopamine (DA). In addition, their effect over granular cerebral cells (CGC) and HeLa cells stressed by ultraviolet irradiation was studied, and treated with ascorbate. Tests with DHR were repeated treating the samples with H2O2 and ascorbate. Pro-oxidant ability tested by both DHR and Tyr fluorescence suggest that ascorbate is antioxidant towards Mn(III)-induced oxidative damage. MnCit and MnPPi (but not EUK8), when in presence of peroxide, are less oxidants. An analogous trend was observed for BSA, although without statistical significance. Evaluation of DA formation by luminescence was inconclusive, but competition studies of DA+DHR mixtures indicated that DA is preferentially oxidized by all the complexes. To CGC, little difference was observed for the toxicities of the complexes. An inverse relationship of toxicity and lipophilicity has been observed. However this was not observed for HeLa cells, to which EUK8 was more toxic. In addition, and in opposition to the DHR solution study, ascorbate was found to be pro-oxidant. A negative synergic effect was observed between complex doses and irradiation. Treatment of the cells with paraaminosalicylate was beneficial only for non-irradiated cells.

Pasture plants already adapted to acidic soil conditions are required as part of an integrated approach (with lime amelioration) to managing acid soils on the Tablelands of New South Wales, Australia. The objective of this thesis is to evaluate the usefulness of Austrodanthonia species for this purpose. The material evaluated in this study was collected during a previous survey of the distribution of Austrodanthonia on the Central, Southern and Monaro Tablelands of New South Wales. It was hypothesised that the genus Austrodanthonia has a wide range of tolerance to acid soils. A series of experiments that provided information on the growth and physiology of Austrodanthonia in relation to soil acidity, with a view to the identification and eventual domestication of the most promising plant material have been conducted through pot, hydroponics and field investigations. Firstly, soils were acidified or limed to obtain a range of soil pH and Al concentrations. This experiment showed that adding aluminium sulfate and calcium carbonate followed by washing excess salts with water is a simple, rapid and convenient method for adjusting soil pH for pot experiments. The pH of the amended soils remained relatively unchanged eight months after treatment. The experimental set-up also resulted in a wide range of soluble Al (2-52 mg/kg) across the soils. The relative Al-tolerance of 183 accessions from 15 Austrodanthonia species was tested in a pot experiment using a range of soil pH. Emergence, survival and growth of all accessions were drastically reduced by high soil acidity (pH 3.9, P < 0.001). About 11% of plants emerged at pH 3.9, whereas at pH 4.4 and 5.3, ~72% of plants emerged. Accessions exhibited large variation within and between species in their tolerance to soil acidity. From the species/accessions tested, 49 accessions from eight species were selected for further study (on the basis of being more acid tolerant). Hydroponic experiments conducted in the glasshouse evaluated: (i) formulation of nutrient solution with a stable pH, (ii) effectiveness of the formulation using tap water and deionised water and (iii) estimation of free ion activities of Al and Mn in the nutrient solution and their effects on Austrodanthonia growth. These experiments showed that a NO3-N/NH4-N ratio of 9:4 is the most appropriate ratio to obtain a stable pH 4.0 without affecting plant growth; that there was little difference between tap water and deionised water on the ionic effects of Al and Mn, and plant-size did not play a role on accession survival and that accessions of Austrodanthonia could grow well within a wide range of pH (3.5-5.5), Al (50-250 �M) and Mn (100-2000 �M). Growth of Austrodanthonia accessions declined under high acidity (pH < 3.5) and Al (300 �M), but tolerated high concentrations of Mn (2000 �M). Root-tips stained with hematoxylin grouped accessions in a similar way to the pot and hydroponic experiments for most of the accessions tested. The intensity of root staining with hematoxylin and the differential distribution of Al in the shoots and roots provided an indication that different tolerance mechanisms may be involved with Austrodanthonia accessions. It appears that both exclusion and internal mechanisms may operate for Al- and Mn-tolerance. A field experiment was conducted at Carcoar (33037�S, 149013�E, elevation 800 m) using gradients in soil pH and Al available on-site to grow selected accessions of Austrodanthonia. The accessions exhibited a range of responses to soil acidity. The accession responses to acidity from the pot and hydroponic experiments were similar to those obtained in the field, especially where Al was present as a low Al-challenge. Overall, this study shows that Austrodanthonia exhibits a wide range of acid tolerance between species and accessions within species. Among the species tested, A. duttoniana and A. fulva appeared to have the greatest commercial potential, because of their productivity and acid tolerance. The variability that exists in the accessions may be exploitable in breeding and selection programs for improved cultivars.

Pasture plants already adapted to acidic soil conditions are required as part of an integrated approach (with lime amelioration) to managing acid soils on the Tablelands of New South Wales, Australia. The objective of this thesis is to evaluate the usefulness of Austrodanthonia species for this purpose. The material evaluated in this study was collected during a previous survey of the distribution of Austrodanthonia on the Central, Southern and Monaro Tablelands of New South Wales. It was hypothesised that the genus Austrodanthonia has a wide range of tolerance to acid soils. A series of experiments that provided information on the growth and physiology of Austrodanthonia in relation to soil acidity, with a view to the identification and eventual domestication of the most promising plant material have been conducted through pot, hydroponics and field investigations. Firstly, soils were acidified or limed to obtain a range of soil pH and Al concentrations. This experiment showed that adding aluminium sulfate and calcium carbonate followed by washing excess salts with water is a simple, rapid and convenient method for adjusting soil pH for pot experiments. The pH of the amended soils remained relatively unchanged eight months after treatment. The experimental set-up also resulted in a wide range of soluble Al (2-52 mg/kg) across the soils. The relative Al-tolerance of 183 accessions from 15 Austrodanthonia species was tested in a pot experiment using a range of soil pH. Emergence, survival and growth of all accessions were drastically reduced by high soil acidity (pH 3.9, P < 0.001). About 11% of plants emerged at pH 3.9, whereas at pH 4.4 and 5.3, ~72% of plants emerged. Accessions exhibited large variation within and between species in their tolerance to soil acidity. From the species/accessions tested, 49 accessions from eight species were selected for further study (on the basis of being more acid tolerant). Hydroponic experiments conducted in the glasshouse evaluated: (i) formulation of nutrient solution with a stable pH, (ii) effectiveness of the formulation using tap water and deionised water and (iii) estimation of free ion activities of Al and Mn in the nutrient solution and their effects on Austrodanthonia growth. These experiments showed that a NO3-N/NH4-N ratio of 9:4 is the most appropriate ratio to obtain a stable pH 4.0 without affecting plant growth; that there was little difference between tap water and deionised water on the ionic effects of Al and Mn, and plant-size did not play a role on accession survival and that accessions of Austrodanthonia could grow well within a wide range of pH (3.5-5.5), Al (50-250 �M) and Mn (100-2000 �M). Growth of Austrodanthonia accessions declined under high acidity (pH < 3.5) and Al (300 �M), but tolerated high concentrations of Mn (2000 �M). Root-tips stained with hematoxylin grouped accessions in a similar way to the pot and hydroponic experiments for most of the accessions tested. The intensity of root staining with hematoxylin and the differential distribution of Al in the shoots and roots provided an indication that different tolerance mechanisms may be involved with Austrodanthonia accessions. It appears that both exclusion and internal mechanisms may operate for Al- and Mn-tolerance. A field experiment was conducted at Carcoar (33037�S, 149013�E, elevation 800 m) using gradients in soil pH and Al available on-site to grow selected accessions of Austrodanthonia. The accessions exhibited a range of responses to soil acidity. The accession responses to acidity from the pot and hydroponic experiments were similar to those obtained in the field, especially where Al was present as a low Al-challenge. Overall, this study shows that Austrodanthonia exhibits a wide range of acid tolerance between species and accessions within species. Among the species tested, A. duttoniana and A. fulva appeared to have the greatest commercial potential, because of their productivity and acid tolerance. The variability that exists in the accessions may be exploitable in breeding and selection programs for improved cultivars.

Os fungos micorrízicos arbusculares são microrganismos com ação extremamente importante em processos fisiológicos de mais de 80% das plantas, ação que acontece devido a uma relação de simbiose entre fungo e planta de onde resultam benefícios para os intervenientes. O presente trabalho pretende avaliar a existência de ligações preferenciais entre FMA e famílias botânicas, assim como avaliar a diversidade funcional dos fungos micorrízicos nativos na proteção do trigo contra toxicidades de Mn. Quando o ERM se manteve intacto após o crescimento do Developer, o trigo apresentou taxas de colonização micorrízica mais elevadas, demonstrando que este beneficiou da presença da rede de micélio intacto previamente desenvolvida pela planta Developer. Relativamente ao Mn na parte aérea do trigo, observaram-se valores de extração de Mn mais altos após a serradela, margaça e erva vaqueira, valores estes que resultaram de um maior crescimento do trigo e não de uma concentração de Mn mais elevada; Functional diversity of Native Mycorrhizal fungi in the Wheat Protection Against Mn toxicity . Abstract: The mycorrhizal fungi are microorganisms with extremely important action in physiological processes of more than 80% of the plants, an action that happens because of a symbiotic relationship between fungi and plant which result benefits to stakeholders. This study aims to assess the existence of preferential links between FMA and botanical families, as well as evaluate the functional diversity of native mycorrhizal fungi on wheat protection Mn toxicities. When the ECM remained intact after the Developer growth, wheat showed higher mycorrhizal colonization rates, demonstrating that this benefit of the presence of intact mycelia previously developed by the plant (Developer). Regarding Mn in wheat were observed Mn extracting values higher after “serradela”, “margaça” “erva vaqueira” , which are values resulted from an increased grain growth and not from a higher Mn concentration.

Foram testadas várias soluções aquosas extractantes (CaC12, KCI, H3PO4, NH4CH3000, H20 com e sem adição de ácido e DTPA) com variação da concentração ou pH e do tempo de agitação, na determinação de magnésio e manganês num solo ácido com toxicidade de manganês com o objectivo de tentar encontrar um método de extracção, que permitisse prever a quantidade dos dois nutrientes absorvida por uma variedade de trigo (Triticum aestivum var. Almansor) para, posteriormente, ser utilizado na previsão do aparecimento de toxicidade de manganês. Para tal, compararam-se os valores de concentração de magnésio e manganês, obtidos com cada condição de extracção, com os valores das mesmas concentrações na planta crescida no mesmo solo. Os valores obtidos, para os coeficientes de determinação (r2) das regressões linares correspondentes, não foram muito elevados o que prova, mais uma vez, a dificuldade de aferição de métodos de determinação de nutrientes no solo, que permitam prever as quantidades absorvidas pela planta. Através de um ensaio em vasos, utilizando o mesmo solo e a mesma variedade de planta, verificou-se qual a variação das quantidades de magnésio, manganês e da sua razão na solução do solo ao longo do tempo, com e sem planta. Além disso, testou-se o efeito provocado na quantidade de matéria seca de planta obtida e nas concentrações dos dois nutrientes e da sua razão na solução do solo e na planta, devido à aplicação de carbonato de cálcio e deste adicionado de sulfato de magnésio. As concentrações de magnésio e manganês nos extractos de solo e nas amostras de planta, e de magnésio na solução do solo foram determinadas utilizando a técnica de espectrofotometria de absorção atómica com chama. Para o manganês na solução do solo, em grande parte das amostras, utilizou-se a técnica de absorção atómica com câmara de grafite. Compararam-se também, os valores das concentrações de magnésio e manganês e da sua razão na solução do solo sem tratamento, com os valores correspondentes na planta. Os coeficientes de determinação (r2) das regressões lineares para estas relações foram muito elevados. Estes resultados parecem indicar que a solução do solo é um meio mais promissor, na determinação das quantidades destes nutrientes e da sua razão, para previsão de toxicidade de manganês, do que a extracção do próprio solo com soluções extractantes. //Abstract - Several extractants solutions (CaC12, KC1, H3PO4, NH4CH3COO, H2O com e sem adição de ácido e DTPA), with variation of its concentration, pH and agitation time, were tested in the determination of magnesium and manganese to predict the development of manganese toxicity for wheat (Triticum aestivum var almansor) in an acid soil. The results of each extractant were compared with those in the plant growth in the same soil. The values of the coefficients of determination (r2) of those relationships were not very good, wich proves oncemore the dificulty and the litle sucess obtained, until now, in relating soil analyses to nutrient plant uptake. The time variation of the manganese and magnesuum concentrations and Mg/Mn ratio in the soil solution were tested, with or without plant, in a pot experiment with the same soil and plant. The effect of calcium carbonate and calcium carbonate with magnesium sulfate addition to the soil in plant dry matter yield, soil solution and plant tissues magnesium and manganese concentrations and its ratio was also studied in the same pot experiment. Manganese and magnesium concentrations in soil extracts and plant tissues and magnesium concentration in soil solution were determined by flame atomic absorption spectrometry. Soil solution manganese, in most samples, was determined by electrothermal atomic absorption spectrometry. Soil solution magnesium, manganese and Mg/Mn ratio were compared with correspondent values in plant tissues. The r2 values obtained for those relationships were very high, which probably means that soil solution can be a more promissor way in predicting nutrient uptake by plant and manganese toxicity.

Vast agricultural areas are affected by flooding causing up to 80% yield reduction and resulting in multibillion dollar losses. In recent years, the occurrence of flooding has increased though human activities, especially in agricultural systems with poor drainage. Therefore, waterlogging stress is becoming one of the main challenge of the modern agriculture. Of all the cereals, barley (Hordeum vulgare L.) is a widely adaptable crop, which is ranked fourth among grains in quantity produced behind maize (Zea mays L.), rice (Oryza sativa L,) and wheat (Triticum aestivum L,). The less complex barley genome also makes it a useful species to understand physiological and molecular aspects of plant adaptation to the flooding stress and to improve their adaptive abilities to confront environmental constrains. Waterlogging tolerance is a complex trait affected by various factors including soil characteristics, temperature, plant developmental stage, microbe activities and oxygen availability. Understanding the mechanisms of waterlogging tolerance make it possible for plant breeders to target individual physiological traits and create barley breeding materials with enhanced waterlogging tolerance. Up to now, the focus of plant breeders was predominantly on alleviating detrimental effects of anoxia, while other (potentially equally important) traits were essentially neglected. One of these is the soil elemental toxicity. Excess water triggers a progressive decrease in the soil redox potential, thus increasing the concentrations of Mn2\(^+\) and Fe2\(^+\) that can be toxic to plants, when exceeding a threshold concentration. Cellular detoxification and exclusion are the main strategies for plants to resist excess ion concentration in soil. However, specific details of their coordination and the relative contribution of these components towards manganese toxicity tolerance in barley have not been fully revealed. Besides, the linkage between ion toxicity tolerance and waterlogging stress tolerance is still poorly understood, although tolerance to one or more elemental toxicities can be an essential trait to improve plant performance in waterlogged soils. Accordingly, the major aim of this PhD project was to investigate the physiological and molecular aspects of manganese toxicity tolerance associated with waterlogging stress tolerance. The following specific objectives were addressed: To quantify the relative contribution of Mn2\(^+\) toxicity to waterlogging stress tolerance; To develop a rapid screening method and screen a large number of barley varieties; To identify QTLs controlling tolerance to manganese toxicity in barley associated with tolerance of waterlogging stress; To investigate physiological and molecular mechanisms conferring manganese tolerance. Working along these lines, a broad range of barley (Hordeum vulgare and Hordeum spontaneum L.) genotypes contrasting in waterlogging stress tolerance were used to investigate its linkage with manganese toxicity tolerance. In total, twenty barley genotypes (including three wild barleys) contrasting in waterlogging stress tolerance were studied for their ability to cope with the toxic (1 mM) amounts of Mn2\(^+\) in the root rhizosphere. Under Mn2\(^+\) toxicity, chlorophyll content of most waterlogging-tolerant genotypes (TX9425, Yerong, CPI-71284-48 and CM72) remained above 60% of the control value, whereas sensitive genotypes (Franklin and Naso Nijo) had a chlorophyll content less than 35% of the control. Manganese concentration in leaves was not related to visual Mn2\(^+\) toxicity symptoms, suggesting that various Mn2\(^+\) tolerance mechanisms might have operated in different tolerant genotypes, i.e. avoidance versus tissue tolerance. The overall significant (r = 0.60) correlation between tolerances to Mn2\(^+\) toxicity and waterlogging in barley suggests that plant breeding for tolerance to waterlogging traits may be advanced by targeting mechanisms conferring tolerance to Mn2\(^+\) toxicity, at least in this species. Direct selection (using only agronomic traits) for stress tolerance is easily affected by environments thus less effective. Marker assisted selection (MAS) could provide an indirect selection process which can effectively reveal distinct genetic differences but not merely on trait itself. Therefore, further studies were conducted in specific doubled-haploid populations to determine whether the same genes are responsible for Mn2\(^+\) and waterlogging tolerance. A total of 177 lines from Yerong/Franklin population were used to identify QTL conferring Mn2\(^+\) tolerance and another 188 DH lines from TX9425/Naso Nijo were used to validate the QTL identified in the Yerong/Franklin population. Seven QTLs were identified from these two populations. Among all, four QTL controlling plant survival under manganese toxicity determined almost 40% of phenotypic variation. Two significant QTL for leaf chlorosis were identified at a similar position as those for plant survival on chromosome 3H and 6H, explaining 22.1% and 7.5% of phenotypic variation respectively. In the TX9425/Naso Nijo DH population, only one significant QTL accounting for plant survival was identified which was located at a same position on chromosome 3H as the major QTL identified in the Yerong/Franklin DH population. Based on the major QTL on chromosome 3H, three candidate genes (POD, KAT3, HMA) for this QTL were identified, suggesting antioxidant system and potassium transport might play a substantial role in coping with manganese toxicity. We then used the MIFE (microelectrode ion flux measurement) technique to study some aspects of manganese stress signalling, focusing on K\(^+\) transport (as per about QTL findings). K\(^+\) retention plays a pivotal role in conferring many abiotic stress tolerances in plants. In this work, ten selected barley genotypes were used to study Mn-induced changes in K\(^+\) transport. These fluxes were then related to appropriate changes in fluxes of Ca2\(^+\)+ (a known second messenger) and H\(^+\) (a proxy for H\(^+\)-ATPase activity). All genotypes responded to Mn treatment by net K\(^+\) influx, while net Ca2\(^+\) and H\(^+\) efflux was observed after adding 1 mM Mn2\(^+\). No significant difference among genotypes was found. Several inhibitors were used to understand the specific signal pathway affected by manganese. Manganese-induced K\(^+\) uptake and Ca2\(^+\) efflux were significantly inhibited by TEA (a blocker of K\(^+\) channels) and vanadate (H\(^+\)-ATPase inhibitor). However, a significant K\(^+\) and Ca2\(^+\) leakage was measured in DPI-pretreated root when applied Mn treatment, suggesting that NADPH-oxidase may play an essential role in regulating Mn uptake. High manganese concentration did not significantly affect net Ca2\(^+\) flux and net K\(^+\) flux in Gd3\(^+\), La3\(^+\) or TG (thapsigargin, endomembrane Ca2\(^+\) channel inhibitor) pretreated roots. The above results suggest that both non-selective cation channels and Ca2\(^+\)/H\(^+\) exchangers contribute to manganese uptake and transport in barley roots. Hypoxic conditions also trigger a burst in reactive oxygen species (ROS), resulting in a significant K\(^+\) efflux. This work has shown that hypoxia enhanced sensitivity to exogenous H\(_2\)O\(_2\) while additional Mn ion efficiently alleviated the impact of hypoxia on intracellular K\(^+\) homeostasis. The reported up-regulated expression of HAK gene also suggests that manganese may play an important role by signalling K\(^+\) deficiency and enabling plants with mechanisms for better K\(^+\) retention to confront stress. In conclusion, this project has found that different barley genotypes adopt different strategies to resist manganese toxicity. Both exclusion and internal tolerance mechanisms contribute to Mn2\(^+\) tolerance. Tolerance to Mn2\(^+\) showed a significant positive correlation with waterlogging tolerance. However, Mn2\(^+\) does not appear to be toxic in roots. The ability of roots to retain K\(^+\) was proven to be one of the key traits conferring tolerance to numerous stress. Mn was able to trigger a hyperpolarisation of the plasma membrane, leading to significant K\(^+\) uptake. NADPH oxidase-mediated apoplastic H\(_2\)O\(_2\) production may be causally related to ROS inducible Ca2\(^+\) uptake systems contributing to Mn uptake. Also, HvHAK5 transporter was found to be involved in maintenance of K\(^+\) content in root, which was identified at the major QTL on chromosome 3H associated with manganese toxicity. This QTL could therefore be used in breeding programs to enhance bothmanganese toxicity tolerance and waterlogging tolerance.

碩士
國立宜蘭大學
化學工程與材料工程學系碩士班
100
The first part of this study investigates the toxicity assessment of three-component Fe-Mn-Al alloy. The interactive toxicity and toxicity distribution of Fe3+、Mn2+ and Al3+ ions are determined and predicted by Probit dose-response model and augmented simplex design method, respectively. Experimental results reveal that the toxicity of Mn2+、Al3+ and Fe3+ single ion is in the order of Mn2+>Al3+>Fe3+. The ternary Fe-Mn-Al system’s EC50 contour plot shows a hump near Mn2+:Al3+=1/2:1/2 and two saddles around pure Mn2+ and pure Al3+ regions, which indicates that Fe-Mn-Al alloy is not suitable for biomedical applications when its chemical composition of selectively leached metal ions approach the saddle regions. Toxicity of Fe-Mn-Al alloy with various chemical compositions can be predicted and verified economically and efficiently using an augmented simplex design. The second part of this study investigates the plasma modification effect on the surface properties of chitosan films. Experimental results show that the hydroxyl and amino groups of the chitosan film can be activated after plasma modification. The activation effect of the chitosan film can be improved after 120s plasma modification. The surface of the chitosan film does not degrade nor fracture after plasma modification. The swelling ratio of the chitosan film can be increased significantly without fracture after plasma modification. The thermal degraded temperatures of the chitosan film with or without plasma modifications are both around 300oC, which is much higher than the martensitic transformation temperatures of most shape memory alloys. The chitosan film after 120s plasma modification treatment does not exhibit significant retard or inhibit effect during biodegradation process.

Climate change contributes to the environmental pressures that the Montado/Dehesa systems are experiencing, leading to an impoverishment of the floristic composition of the understorey. The strongly acidic soils of these systems are associated with nutrient deficiencies, nutritional disorders and the toxicity of metals, especially Mn and Al; these problems are discussed with emphasis on the antagonism between Fe and Mn and the relationship between K concentration and Mg uptake and concentration. The potential for the use of the legume-rhizobia symbiosis to increase biological nitrogen fixation and avenues for research are discussed. The co-colonization of the roots of legumes with arbuscular mycorrhizal (AM) fungi and the effects on P and Mn uptake are discussed. A better understanding of the relationships between soil pH, organic matter content (SOM), microbial community, soil P content and the plant strategies to mobilize it, as well as plant effects on the soil solution concentrations of Mn, is important for the management of these systems. The increase of biological nitrogen fixation in these systems, through the breeding of tolerant cultivars to acidic soils and a stepwise legumes enrichment, alongside soil fertility management, may contribute to increasing biomass production, SOM content and overall ecological plasticity.

Potentially toxic elements (PTEs) contamination in soils threats human wellbeing and ecological health because of their toxicity and bioaccumulation. This research presents a portable Olympus Delta Premium 6000 Series XRF Analyser (Olympus, USA) as a rapid measurement tool (RMT) for PTEs: Cr, Cu, Fe, Pb, Mn, and Zn in contaminated soils in the Niger Delta, Nigeria. A total of 45 crude oil-contaminated soils were collected from three genuinely oil spill sites. The range of measured PTEs concentrations (mg/kg) in the study sites are as follows: Site 1: chromium (Cr) 54–75, copper (Cu) 5.4–16.6, iron (Fe) 14,841–23,404, lead (Pb) 13.5–21.4, manganese (Mn) 158–555, and zinc (Zn) 32.6–47.2; Site 2: (35–66), (5–16.1), (10166–20,967), (12–17.8), (209–440), (17.6–33.6); and Site 3: (32–115), (6.5–20.8), (7538–22,800), (12–135), (98–338), (19.9–177). The trend of PTEs across the three sites follows the same order: Fe > Mn > Cr > Zn > Pb > Cu. The average concentration values of PTEs in all the 3 sites were higher than background concentration values. Thus, crude oil spill spiked the PTEs concentrations. XRF spectroscopy is recommended as a cost-effective and RMT for PTEs in soils.

Micronutrients needed by plants are Cu, Fe, Mn, Zn, B, Mo, Cl, Ni, Co, V, Si, and Na. The required amounts of each of these elements is very small but still essential for desirable plant growth and reproduction. These elements must be applied to soils cautiously for the range between deficient and toxic is very small. It is unwise to use a fertilizer containing all of these micronutrients. Any one of them may already be high enough in soils to cause toxicity from that particular element. If a micronutrient is suspected of being deficient, it would be wise to get soil tests and plant tissue tests to corroborate your suspicions. If a micronutrient is deficient, one should apply only the amount recommended but no more. Sometimes a toxicity of an element is more difficult to correct than a deficiency. Copper, iron, manganese, cobalt, and zinc can be present in soils as (a) several types of precipitates, (b) adsorbed onto the surface of soil particles, (c) present in primary minerals (rocks) and secondary minerals (clays), and (d) present as complex ring compounds. These forms may or may not be available to plants. Precipitates of Cu, Fe, Mn, or Zn often form in soils at high pH (after liming Fig. 14.1). This may occur in soils near buildings from the lime used in the mortar. Soil acids dissolve the lime into Ca++ or Mg++ that migrate into the soil raising the pH and cause these micronutrients to precipitate. Often an Fe deficiency is evident, particularly on acid-loving plants, such as azaleas, rhododendrons, or hollies. If this is extensive, the soil near the buildings may need to be replaced. With limited areas, the soil can be acidified by adding elemental S near the plants affected. The elements Cu, Fe, Mn, and Zn can exist as soluble forms or precipitates, depending on the pH of the soil. The soluble forms as cations are present when soils have poor internal drainage (poorly drained soils), whereas the oxides of these elements are present where the soil is well aerated.

Vegetables are a prevalent nutrition for people all over the world because they are high in important nutrients, antioxidants, and metabolites that function as buffers for acidic compounds created during digestion. Vegetables, on the other hand, absorbed both vital and poisonous substances through the soil. Possible human health concerns, including as cancer and renal damage, have been linked to the consumption of heavy metal-contaminated vegetables (HMs). Heavy metals like Cr, Mn, Fe, Ni, Cu, Zn, Cd, Pb, and Hg were found in high concentrations in popular vegetables such as Amaranthus tricolour L., Chenopodium album L., Spinacia oleracea, Coriandrum sativum, Solanum lycopersicum, and Solanum melongena. The toxicity, fortification, health hazard, and heavy metals sources grown in soil are detailed in this review study.

The waste of trace metals are led the pollutions of water, soil and air. That’s why the accurate and sensitive identification of amount of trace metals in food samples and environment are gained importance in analytical chemistry because of their toxicity to human health. Besides, the direct determination of trace metals, presented at very low concentration especially in real samples, is difficult. In this content, before determination of trace metals by instrumental methods can be achieved successfully using separation/preconcentration procedures. The different synthesized chelating polymer resin adsorbents are successfully used for the SPE of trace metals. The trace metals, such as Cu, Cr, Co, Mn, Zn and Fe, are necessary for human health, when it has been taken at certain limits. But, the trace metals, such as Hg, Cd, Pb, Ni and As are toxic metals for the human body. About this, there are studies on the determination of trace elements and mineral in food samples and environment. In this study, new methods in the synthesis of (meth)acrylamides and use as a sorbent in the trace metals extraction was identified.

Exposure to fine particulate matter (PM2.5) and ozone (O3) above US EPA standards is associated with Alzheimer’s disease (AD) risk, while Mn toxicity induces parkinsonism. Mexico City Metropolitan Area (MCMA) children have pre- and postnatal sustained and high exposures to PM2.5, O3, polycyclic aromatic hydrocarbons, and metals. Young MCMA residents exhibit frontal tau hyperphosphorylation and amyloid-β (Aβ)1–42 diffuse plaques, and aggregated and hyperphosphorylated α-synuclein in olfactory nerves and key brainstem nuclei. We measured total prion protein (TPrP), total tau (T-tau), tau phosphorylated at threonine 181 (P-Tau), Aβ1–42, α-synuclein (t-α-syn and d-α-synuclein), BDNF, insulin, leptin, and/or inflammatory mediators, in 129 normal CSF samples from MCMA and clean air controls. Aβ1–42 and BDNF concentrations were significantly lower in MCMA children versus controls (p = 0.005 and 0.02, respectively). TPrP increased with cumulative PM2.5 up to 5 μg/m3 and then decreased, regardless of cumulative value or age (R2 = 0.56). TPrP strongly correlated with T-Tau and P-Tau, while d-α-synuclein showed a significant correlation with TNFα, IL10, and IL6 in MCMA children. Total synuclein showed an increment in childhood years related to cumulated PM2.5, followed by a decrease after age 12 years R2 = 0.47), while d-α-synuclein exhibited a tendency to increase with cumulated PM2.5 (R2 = 0.30). CSF Aβ1–42, BDNF, α-synuclein, and TPrP changes are evolving in young MCMA urbanites historically showing underperformance in cognitive processes, odor identification deficits, downregulation of frontal cellular PrP, and neuropathological AD and PD hallmarks. Neuroprotection of young MCMA residents ought to be a public health priority.