The Physiology of Manganese Toxicity

Horst, Walter J.

doi:10.1007/978-94-009-2817-6_13

Cited by 162 publications

(84 citation statements)

References 82 publications

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“…However, expression of Mn toxicity often varies among crop species (2). Within a crop species, genotypes have been found to show considerable differences in resisting Mn toxicity (11). Various mechanisms have been proposed to explain Mn tolerance.…”

Section: Methodsmentioning

confidence: 99%

Surface Chemical Properties of Purified Root Cell Walls from Two Tobacco Genotypes Exhibiting Different Tolerance to Manganese Toxicity

Wang¹,

Evangelou²,

Nielsen³

1992

Plant Physiol.

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Surface chemical characteristics of root cell walls extracted from two tobacco genotypes exhibiting differential tolerance to Mn toxicity were studied using potentiometric pH titration and Fourier transform infrared spectroscopy. The Mn-sensitive genotype KY 14 showed a stronger interaction of its cell wall surface with metal ions than did the Mn-tolerant genotype Tobacco Introduction (T.l.) 1112. This observation may be attributed to the relatively higher ratio of COO to COOH in KY 14 cell walls than that found in the cell walls of T.I. 1 1 12 in the pH range of 4 to 10. For both genotypes, the strength of binding between metal ions and cell wall surface was in the order of Cu > Ca > Mn > Mg > Na. However, a slightly higher preference of Ca over Mn was observed with the T.l. 1112 cell wall. This may explain the high accumulation of Mn in the leaves of Mn-tolerant genotype T.l. 1112 rather than the high accumulation of Mn in roots, as occurred in Mn-sensitive KY 14. It is concluded that surface chemical characteristics of cell walls may play an important role in plant metal ion uptake and tolerance.Recently, more evidence has suggested that cell wall exchange properties may well affect ion availability for uptake, diffusion rates in the apoplast, the chemical and electrical environment of the membrane and its transporters, growth of the cell wall, and function of cell wall enzymes (1). Therefore, an evaluation of the role of the root cell wall in the processes of metal ion uptake and tolerance is indeed necessary.In this study, purified cell wall materials from two tobacco (Nicotiana tabacum L.) genotypes demonstrating different tolerance to Mn toxicity were investigated. The study examined the intrinsic surface chemical characteristics of root cell walls and related these characteristics to genotypic differences in Mn uptake and tolerance. MATERIALS AND METHODSMn toxicity has been a significant growth-limiting factor for many crops in various regions, especially where crops are grown in relatively low pH soils (e.g. pH < 5.5 (14,19,20) and trichomes (3). The Mn trapped in plant vacuoles has been speculated to be complexed with organic acids (14). This hypothesis is supported by thermodynamic predictions using computer simulation models (24,25 Plant Physiol. Vol. 100, 1992 equilibrated for a relatively long period (e.g. 20 h). The titration curves shown in Figure 2 obtained with a 30-min equilibration period imply that the neutralization reaction between OH-and the H-form of the cell wall of KY 14 genotype in the Na solution background may be faster than that of T.I. 1112. This result indicates that the architecture and/or composition of the cell walls of the two genotypes are different.The shape of the titration curve of KY 14 in Figure 2 suggests that there are at least two apparent pKas in the cell wall material. However, the pKas obtained from such a titration plot cannot be considered as intrinsic pKas because the latter require additional information on ionic strength effect and residue ...

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Section: Methodsmentioning

confidence: 99%

Surface Chemical Properties of Purified Root Cell Walls from Two Tobacco Genotypes Exhibiting Different Tolerance to Manganese Toxicity

Wang¹,

Evangelou²,

Nielsen³

1992

Plant Physiol.

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“…The oxidation of Mn II and phenolic compounds catalyzed by peroxidase (apoplastic peroxidase [POD]) in the leaf apoplast is considered as a key reaction leading to Mn toxicity symptoms and finally leaf injury in cowpea (Vigna unguiculata L. Walp. ;Horst, 1988). This assumption is based mainly on two observations: (1) Mn toxicity symptoms (brown spots on leaves) occur in the cell wall and consist of oxidized Mn and oxidized phenolic compounds , (2) Mann (1950, 1956) observed a close relationship between POD-catalyzed phenol and Mn oxidation.…”

mentioning

confidence: 99%

“…This assumption is based mainly on two observations: (1) Mn toxicity symptoms (brown spots on leaves) occur in the cell wall and consist of oxidized Mn and oxidized phenolic compounds , (2) Mann (1950, 1956) observed a close relationship between POD-catalyzed phenol and Mn oxidation. The oxidation of Mn II and phenols is probably mediated by the formation of highly reactive Mn III and phenoxyradicals, which are considered as phytotoxic agents (Horst, 1988;. Particularly the simultaneous enhancement of POD activity and expression of Mn toxicity symptoms (brown spots) suggest a close relationship between PODs and the oxidation of Mn and phenolic compounds (Fecht-Christoffers et al, 2003a, 2003b.…”

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confidence: 99%

The Role of Hydrogen Peroxide-Producing and Hydrogen Peroxide-Consuming Peroxidases in the Leaf Apoplast of Cowpea in Manganese Tolerance

et al. 2006

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The apoplast is considered the leaf compartment decisive for manganese (Mn) toxicity and tolerance in cowpea (Vigna unguiculata). Particularly apoplastic peroxidases (PODs) were proposed to be key enzymes in Mn toxicity-induced processes. The presented work focuses on the characterization of the role of hydrogen peroxide (H 2 O 2 )-producing (NADH peroxidase) and H 2 O 2 -consuming peroxidase (guaiacol POD) in the apoplastic washing fluid (AWF) of leaves for early stages of Mn toxicity and genotypic differences in Mn tolerance of cowpea. Leaf AWF of the Mn-sensitive cultivar (cv) TVu 91 but not of the Mntolerant cv 1987 showed an increase of guaiacol-POD and NADH-peroxidase activities at elevated AWF Mn concentrations. two-dimensional resolutions of AWF proteins revealed that cv TVu 91 expressed more and additional proteins at high Mn treatment, whereas Mn-tolerant cv TVu 1987 remained nearly unaffected. In both cultivars, NADH-peroxidase activity and accompanied H 2 O 2 formation rate in vitro were significantly affected by Mn 21 , p-coumaric acid, and metabolites occurring in the AWF. The total phenol concentration in the AWF was indicative of advanced stages of Mn toxicity but was rather unrelated to early stages of Mn toxicity and genotypic differences in Mn tolerance. The NADH oxidation by AWF PODs was significantly delayed or enhanced in the presence of the protein-free AWF from cv TVu 1987 or cv TVu 91, respectively. High-performance liquid chromatography analysis of AWF indicates the presence of phenols in cv TVu 1987 not observed in cv TVu 91. We conclude from our studies that the H 2 O 2 -producing NADH peroxidase and its modulation by stimulating or inhibiting phenolic compounds in the leaf apoplast play a major role for Mn toxicity and Mn tolerance in cowpea.

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“…However, the response of plants to excess Mn is affected by leaf age (Horst, 1988), temperature (Heenan and Carter, 1977;Rufty et al, 1979), soil nutrient balance, soil pH, genotype, and light intensity. The effect of light intensity on Mn-toxicity symptoms was first reported in 1935, when McCool (1935) found that plants grown in low light displayed fewer symptoms of Mn toxicity than those grown in high light.…”

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confidence: 99%

Light and Excess Manganese

1998

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The effect of light intensity on antioxidants, antioxidant enzymes, and chlorophyll content was studied in common bean (Phaseolus vulgaris L.) exposed to excess Mn. Leaves of bean genotypes contrasting in Mn tolerance were exposed to two different light intensities and to excess Mn; light was controlled by shading a leaflet with filter paper. After 5 d of Mn treatment ascorbate was depleted by 45% in leaves of the Mn-sensitive genotype ZPV-292 and by 20% in the Mn-tolerant genotype CALIMA. Nonprotein sulfhydryl groups and glutathione reductase were not affected by Mn or light treatment. Ten days of Mn-toxicity stress increased leaf ascorbate peroxidase activity of cv ZPV-292 by 78% in low light and by 235% in high light, and superoxide dismutase activity followed a similar trend. Increases of ascorbate peroxidase and superoxide dismutase activity observed in cv CALIMA were lower than those observed in the susceptible cv ZPV-292. The cv CALIMA had less ascorbate oxidation under excess Mn-toxicity stress. Depletion of ascorbate occurred before the onset of chlorosis in Mn-stressed plants, especially in cv ZPV-292. Lipid peroxidation was not detected in floating leaf discs of mature leaves exposed to excess Mn. Our results suggest that Mn toxicity may be mediated by oxidative stress, and that the tolerant genotype may maintain higher ascorbate levels under stress than the sensitive genotype.

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The Physiology of Manganese Toxicity

Cited by 162 publications

References 82 publications

Surface Chemical Properties of Purified Root Cell Walls from Two Tobacco Genotypes Exhibiting Different Tolerance to Manganese Toxicity

Surface Chemical Properties of Purified Root Cell Walls from Two Tobacco Genotypes Exhibiting Different Tolerance to Manganese Toxicity

The Role of Hydrogen Peroxide-Producing and Hydrogen Peroxide-Consuming Peroxidases in the Leaf Apoplast of Cowpea in Manganese Tolerance

Light and Excess Manganese

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