ascorbic-acid and arsenic-acid

Arsenic (As) is the most hazardous soil contaminant, which inactivates metabolic enzymes and restrains plant growth. To withstand As stress conditions, use of some alleviative tools, such as arbuscular mycorrhizal (AM) fungi and silicon (Si), has gained importance. Therefore, the present study evaluated comparative and interactive effects of Si and arbuscular mycorrhiza-Rhizophagus irregularis on phytotoxicity of arsenate (As V) and arsenite (As III) on plant growth, ROS generation, and antioxidant defense responses in pigeonpea genotypes (Tolerant-Pusa 2002; Sensitive-Pusa 991). Roots of As III treated plants accumulated significantly higher total As than As V supplemented plants, more in Pusa 991 than Pusa 2002, which corresponded to proportionately decreased plant growth, root to biomass ratio, and oxidative burst. Although Si nutrition and AM inoculations improved plant growth by significantly reducing As uptake and the resultant oxidative burst, AM was relatively more efficient in upregulating enzymatic and non-enzymatic antioxidant defense responses as well as ascorbate-glutathione pathway when compared with Si. Pusa 2002 was more receptive to Si nourishment due to its ability to establish more efficient mycorrhizal symbiosis, which led to higher Si uptake and lower As concentrations. Moreover, +Si+AM bestowed better metalloid resistance by further reducing ROS and strengthening antioxidants. Results demonstrated that the genotype with more efficient AM symbiosis in As-contaminated soils could accrue higher benefits of Si fertilization in terms of metalloid tolerance in pigeonpea.

Topics: Antioxidants; Arsenates; Arsenic; Arsenites; Ascorbic Acid; Biomass; Cajanus; Genotype; Glomeromycota; Glutathione; Mycorrhizae; Plant Development; Plant Roots; Silicon; Soil Pollutants; Symbiosis; Vanadium

The present study is aimed to investigate whether ascorbate-glutathione cycle (AsA-GSH cycle) or thiol metabolism is involved in the regulation of arsenate (As(V))-induced oxidative stress and tolerance in ridged Luffa seedlings. As(V) significantly (p < 0.05) declined the growth of Luffa seedlings which was accompanied by the enhanced accumulation of As. The enhanced accumulation of As in tissues declined total protein and nitrogen contents and photosynthesis, and increased the accumulation of reactive oxygen species (ROS). The enhanced levels of ROS cause damage to lipids and proteins as indicated by the increased contents of malondialdehyde (MDA) and reactive carbonyl groups (RCG). The components of AsA-GSH cycle such as ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase, and reduced ascorbate were downregulated, while glutathione reductase and glutathione were upregulated by As(V) stress. Thiol metabolic enzymes such as cysteine synthase, γ-glutamylcysteine synthetase, and glutathione synthetase, and compounds such as cysteine, glutathione, and non-protein thiols were stimulated by As(V) stress. These results suggest that thiol metabolism plays a key role in mitigating As(V)-mediated further damage to Luffa seedlings, while AsA-GSH cycle components had a little role in imparting As(V) tolerance. The present study provides information regarding the involvement of AsA-GSH cycle and thiol metabolism in imparting As(V) tolerance in Luffa. The results of this study can be utilized for As(V) toxicity management in Luffa while keeping these biochemical components into consideration.

Topics: Adaptation, Physiological; Arsenates; Ascorbic Acid; Chlorophyll; Glutathione; Luffa; Metabolic Networks and Pathways; Oxidative Stress; Plant Proteins; Reactive Oxygen Species; Seedlings; Soil Pollutants; Sulfhydryl Compounds

In plants, hydrogen sulfide (H2S) is an emerging novel signaling molecule that is involved in growth regulation and abiotic stress responses. However, little is known about its role in the regulation of arsenate (As(V)) toxicity. Therefore, hydroponic experiments were conducted to investigate whether sodium hydrosulfide (NaHS; a source of H2S) is involved in the regulation of As(V) toxicity in pea seedlings. Results showed that As(V) caused decreases in growth, photosynthesis (measured as chlorophyll fluorescence) and nitrogen content, which was accompanied by the accumulation of As. As(V) treatment also reduced the activities of cysteine desulfhydrase and nitrate reductase, and contents of H2S and nitric oxide (NO). However, addition of NaHS ameliorated As(V) toxicity in pea seedlings, which coincided with the increased contents of H2S and NO. The cysteine level was higher under As(V) treatment in comparison to all other treatments (As-free; NaHS; As(V)+NaHS). The content of reactive oxygen species (ROS) and damage to lipids, proteins and membranes increased by As(V) while NaHS alleviated these effects. Enzymes of the ascorbate-glutathione cycle (AsA-GSH cycle) showed inhibition of their activities following As(V) treatment while their activities were increased by application of NaHS. The redox status of ascorbate and glutathione was disturbed by As(V) as indicated by a steep decline in their reduced/oxidized ratios. However, simultaneous NaHS application restored the redox status of the ascorbate and glutathione pools. The results of this study demonstrated that H2S and NO might both be involved in reducing the accumulation of As and triggering up-regulation of the AsA-GSH cycle to counterbalance ROS-mediated damage to macromolecules. Furthermore, the results suggest a crucial role of H2S in plant priming, and in particular for pea seedlings in mitigating As(V) stress.

Topics: Arsenates; Ascorbic Acid; Biomass; Cell Membrane; Chlorophyll; Cystathionine gamma-Lyase; Cysteine; Fluorescence; Glutathione; Hydrogen Sulfide; Lipid Metabolism; Nitrate Reductase; Nitric Oxide; Nitrogen; Pisum sativum; Plant Proteins; Reactive Oxygen Species; Seedlings; Up-Regulation

In this study we evaluated the arsenate adsorption capacity of red muds (RM), wastes tailing from the alumina production, at different pH values (4, 7, and 10). RM samples were artificially enriched in batch tests with solutions containing increasing concentrations of As(V). The pH of the solution significantly affected the adsorption, which increased with the decrease of pH. Moreover a sequential extraction procedure [H(2)O; (NH(4))(2)SO(4); NH(4)H(2)PO(4); NH(4)(+)-oxalate; NH(4)(+)-oxalate+ascorbic acid] was applied to RM samples exchanged with arsenate. Using this approach it was shown that low concentrations of arsenate sorbed in RM were present as water soluble and exchangeable fractions, while NH(4)(+)-oxalate and NH(4)(+)-oxalate+ascorbic acid extracted most of the adsorbed arsenate from RM at different pH values. Besides, FT-IR spectroscopy was used to better understand the nature of RM surface configuration after As(V) sorption. In the FT-IR spectra the presence of As(V) species was highlighted by a well resolved band at 865 cm(-1). The intensity and broadness of this band increased at the decreasing of pH. This band could be related to nu(As-O) vibration of an inner-sphere Al-O-As complex and/or due to As-O bonds of the adsorbed As(V) species on Fe oxides of RM samples.

Topics: Adsorption; Aluminum; Aluminum Oxide; Arsenates; Ascorbic Acid; Environmental Monitoring; Ferric Compounds; Hydrogen-Ion Concentration; Industrial Waste; Oxalates; Oxides; Spectroscopy, Fourier Transform Infrared; Surface Properties; Water Pollutants, Chemical; Water Purification; X-Ray Diffraction

We have modified an automated measurement system of urinary iodine (UI) and established a sensitive UI assay system by using ultraviolet (UV) digestion. The automated system is sensitive enough to detect concentrations of UI < 0.78 mumol/L (< 10 micrograms/dL) in a small volume of urine (500 microL). Sample throughput is > 30/h, including a water washing. The within-assay imprecision (CV) was < or = 10% in the UI range of 0.10-3.00 mumol/L; the between-assay CV was usually < or = 15% in the same range. Analytical recovery of iodine added to urine samples was consistently > 90%. The theoretical values were recovered when UV irradiation was used but not in its absence. High (supraphysiological) doses of thiocyanate or ascorbic acid, which are major interfering substances to the ceric-arsenious acid reaction, did not interfere with this system. The correlation between UI determined by this method and by the acid digestion method was linear (r = 0.994). For samples containing iodine at < 1.00 mumol/L, the correlation between values by both methods was still significant (r = 0.937). UI in an iodine-deficient area in Ukraine, measured by this system, ranged from 0.06 to 1.83 mumol/L (median 0.44 mumol/L, n = 95), significantly lower than in Japan (range 0.23-50.70 mumol/L, median 4.70 mumol/L, n = 84) and consistent with mild iodine deficiency. This modified automated assay system, therefore, is useful and applicable for screening UI in inhabitants of iodine-deficient areas.

Topics: Arsenates; Ascorbic Acid; Autoanalysis; Cerium; Humans; Iodine; Japan; Quality Control; Reference Values; Sensitivity and Specificity; Sulfates; Thiocyanates; Ukraine; Ultraviolet Rays

Topics: Arsenates; Ascorbic Acid; Cerium; Humans; Iodine; Male; Middle Aged; Reproducibility of Results