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Active Oxygen Species (active + oxygen_species)
Selected AbstractsDifferential Responses of the Activities of Antioxidant Enzymes to Thermal Stresses between Two Invasive Eupatorium Species in ChinaJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 4 2008Ping Lu Abstract The effect of thermal stress on the antioxidant system was investigated in two invasive plants, Eupatorium adenophorum Spreng. and E. odoratum L. The former is sensitive to high temperature, whereas the latter is sensitive to low temperature. Our aim was to explore the relationship between the response of antioxidant enzymes and temperature in the two invasive weeds with different distribution patterns in China. Plants were transferred from glasshouse to growth chambers at a constant 25 °C for 1 week to acclimatize to the environment. For the heat treatments, temperature was increased stepwise to 30, 35, 38 and finally to 42 °C. For the cold treatments, temperature was decreased stepwise to 20, 15, 10 and finally to 5 °C. Plants were kept in the growth chambers for 24 h at each temperature step. In E. adenophorum, the coordinated increase of the activities of antioxidant enzymes was effective in protecting the plant from the accumulation of active oxygen species (AOS) at low temperature, but the activities of catalase (CAT), guaiacol peroxidase (POD), ascorbate peroxidase (APX), glutathione reductase (GR), and monodehydroascorbate reductase (MDAR) were not accompanied by the increase of superoxide dismutase (SOD) during the heat treatments. As a result, the level of lipid peroxidation in E. adenophorum was higher under heat stress than under cold stress. In E. odoratum, however, the lesser degree of membrane damage, as indicated by low monodehydroascorbate content, and the coordinated increase of the oxygen. Detoxifying enzymes were observed in heat-treated plants, but the antioxidant enzymes were unable to operate in cold stress. This indicates that the plants have a higher capacity for scavenging oxygen radicals in heat stress than in cold stress. The different responses of antioxidant enzymes may be one of the possible mechanisms of the differences in temperature sensitivities of the two plant species. [source] Diesel particulate matter and NOx removals using a pulsed corona surface dischargeAICHE JOURNAL, Issue 3 2004S. Yao Abstract A pulsed corona surface discharge (PCSD) system was established for particulate matter (PM) and NOx removals from a diesel engine. The PCSD was carried out with a dielectric barrier discharge (DBD) reactor and a pulse power supply at atmospheric pressure and room temperature. The DBD reactor consisted mainly of an alumina (Al2O3) tube and a stainless steel rod (cathode) inserted in the alumina tube, and an aluminum coil (anode) wound on the outside surface of the Al2O3 tube. Pulse voltage was applied to the outside Al coil and stainless steel rod. PM was removed at a rate of 89% at maximum with 40% NOx removal. Relations of pulse voltage and frequency to PM and NOx removals were investigated. PM was oxidized by NO2 and other kinds of active oxygen species, such as O and O3 from plasma discharges. A surface adsorption/desorption and PM oxidation model of PM removal was established. The kinetic equations and their constants were given. © 2004 American Institute of Chemical Engineers AIChE J, 50:715,721, 2004 [source] Hydrogen peroxide concentration measured in cultivation substrates during growth and fruiting of the mushrooms Agaricus bisporus and Pleurotus spp.JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 7 2007Jean-Michel Savoie Abstract Hydrogen peroxide is suspected of being highly implicated in mushroom nutrition and in substrate bleaching during cultivation. The parameters for measuring H2O2 in compost samples were examined and the methodology was applied to samples from both compost colonized by cultivars and wild isolates of Agaricus bisporus, and wheat straw or coffee pulp colonized by Pleurotus spp. Laccase and peroxidase activities were also measured. H2O2 concentration measured after heating at 80 °C for inactivating laccases and peroxidases was probably both H2O2 pre-existing in the compost and H2O2 generated from quinones and active oxygen species. This potential H2O2 concentration increased during the vegetative growth for all the strains, in agreement with a direct relationship between H2O2 concentration and active biomass of A. bisporus or Pleurotus spp. in their cultivation substrates. Correlations were observed between H2O2 concentration and manganese peroxidase activity in cultivation substrates at the stage of primordia formation. At this stage of development, H2O2 generation via biotic or abiotic mechanisms should be an important physiological trait of mushrooms. Copyright © 2007 Society of Chemical Industry [source] Early signalling events in the Avr9/Cf-9-dependent plant defence responseMOLECULAR PLANT PATHOLOGY, Issue 1 2000Tina Romeis Resistance of tomato to the leaf mould fungus Cladosporium fulvum is controlled by the interaction between a plant-encoded resistance gene (Cf-9) and pathogen-encoded avirulence (Avr9) gene. Our objective is to understand the underlying molecular mechanisms that transmit the Cf-9/Avr9-dependent pathogen perception event and activate the plant defence response. Our approach toward the understanding of Cf -function is based on the analysis of early Cf-9/Avr9-mediated responses and signalling events. Because Cf-9 transgenically expressed in tobacco retains its specificity and activity to the Avr9 elicitor, signalling experiments were conducted in the heterologous system using these transgenic lines or derived Cf9 tobacco cell cultures. Among the earliest responses to the Avr9/Cf-9 elicitation event were rapid changes in ion-fluxes, the synthesis of active oxygen species (AOS), probably catalysed by a plant NADPH-oxidase, and the transient activation of two MAP kinases. These kinases were identified as WIPK (wounding-induced protein kinase) and SIPK (salicylic-acid induced kinase) from tobacco. Studies with pharmacological inhibitors suggested that the MAP kinases are located in an independent signalling pathway from the Avr9/Cf-9-dependent synthesis of AOS. SIPK and WIPK were involved in pathogen-related elicitation processes as well as in abiotic stress responses. This indicates that the plant defence is triggered via a signalling network that shares components with pathways originating from abiotic environmental stress stimuli. [source] Co-induction of glutathione- S -transferases and multidrug resistance associated protein by xenobiotics in wheat,PEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 2 2003Frederica L Theodoulou Abstract Herbicide safeners are known to protect monocotyledonous crops from herbicide injury by accelerating the metabolism of herbicides. We have investigated the effects of the safener cloquintocet-mexyl, which protects small-grain cereals against the graminicidal herbicide, clodinafop-propargyl. Subtractive suppression hybridisation was used to identify wheat genes which are up-regulated by treatment not only with cloquintocet-mexyl but also with phenobarbital, which is known to stimulate xenobiotic metabolism in animals and plants. DNA sequences of five glutathione transferases (GSTs) belonging to three different classes and a multidrug resistance associated protein (MRP) homologue were identified in the screen. The chemical inducibility of these clones was confirmed by Northern analysis. The MRP protein was shown to be induced by treatments with cloquintocet-mexyl and phenobarbital and to be localised to the tonoplast. Since clodinafop-propargyl is not known to be metabolised by glutathionylation, the significance of GST induction is interpreted in terms of a generalised response to chemical stress, particularly the generation of active oxygen species. This work establishes herbicide safeners as useful tools for the identification of genes encoding herbicide-metabolising enzymes. © 2003 Society of Chemical Industry [source] Inhibition of the development of leaf rust (Puccinia recondita) by treatment of wheat with allopurinol and production of a hypersensitive-like reaction in a compatible hostPLANT PATHOLOGY, Issue 3 2000A. L. Ádám The effect of allopurinol [4-hydroxypyrazolo (3,4- d) pyrimidine], a purine analogue inhibitor of xanthine oxidase (XO) enzyme, was studied in the host,pathogen combination of Triticum aestivum,Puccinia recondita f.sp. tritici. Analysis of purines and pyrimidines in the allopurinol-treated wheat seedlings showed marked accumulation of xanthine, suggesting the inplanta inhibition of XO activity. In the incompatible wheat,rust interaction application of allopurinol as a drench, even at the highest concentration (50 ,m), did not change the hypersensitive reaction phenotype; only the number of lesions was slightly reduced. Allopurinol treatment decreased the augmented rate of electrolyte leakage and lipid peroxidation associated with the hypersensitive response (HR), an effect probably related to the inhibition of rust development by allopurinol. By contrast, in the case of the compatible wheat,leaf-rust combination the reaction type was strongly affected. The formation of uredia and production of uredospores were diminished or completely inhibited depending on the concentration of allopurinol, which was applied either as a drench (3.125,50 ,m) or as a foliar spray (100,400 ,m) to plants grown in perlite. At the highest allopurinol concentration in the drench, the compatible reaction type changed to a hypersensitive-like necrotic reaction. Significant increases in electrolyte leakage and lipid peroxidation (characteristic of the HR) were found 4,6 days after infection in susceptible plants treated with allopurinol. Staining of leaf slices from allopurinol-treated and compatible rust-infected plants with Evans blue indicated cell death surrounding the pustules, while at this stage no cell death was detected in infected leaves without allopurinol treatment. The above results suggest that XO is not the main source of the generation of active oxygen species in wheat during the HR to leaf rust. [source] Direct Oxidation of Benzene to Phenol by Dioxygen over Nano-vanadium OxideCHINESE JOURNAL OF CHEMISTRY, Issue 11 2009Xiaohan Gao Abstract Reducing regents, such as ascorbic acid, are needed for vanadium-containing catalysts to catalyze the direct oxidation of benzene to phenol by dioxygen. Quadrivalent vanadium species, reduced from quinquevalent vanadium species, can activate dioxygen to produce active oxygen species, which is important for the reaction. The key step is to prepare more V4+ -containing catalysts. Here, VOX -C16 -A was prepared in an acidic medium to produce more V4+ species. The results of XPS and XRD studies confirmed that the vanadium species in VOX -C16 -A was mainly V4+ ions. The results of XRD and electron diffraction patterns revealed that VOX -C16 -A consisted of tetragonal VO2 and monoclinic VO2. Morphology observations display that the VOX -C16 -A is made of nanorod. Investigations into the performances of the catalysts showed that VOX -C16 -A was reusable, producing a 1.9% conversion of benzene without reducing agent. [source] | |||||||||||||