The involvement of oxygen-derived free radicals in plant–pathogen interactions

1994 ◽  
Vol 102 ◽  
pp. 479-493
Author(s):  
B. A. Goodman
Keyword(s):  
Free Radicals ◽  
Free Radical ◽  
Atmospheric Oxygen ◽  
Oxygen Species ◽  
Defence Mechanisms ◽  
Paramagnetic Resonance ◽  
Radical Intermediates ◽  
Oxygen Derived Free Radicals ◽  
Plant Pathogen Interactions ◽  
Electron Paramagnetic

SynopsisPlants have evolved a multiplicity of defence mechanisms against pathogen attack. Their modes of action may be to (i) kill the pathogen directly, (ii) block the action of enzymes required for infection, or (iii) erect barriers to pathogen growth. Some of these reactions proceed via free radical intermediates and make use of either atmospheric oxygen or reactive oxygen species. This paper reviews the various types of reaction involving oxygen-derived free radicals that are initiated in plant tissue when it is invaded by pathogenic organisms. Both the production of free radicals by plants in defensive processes and the utilisation of free radicals by pathogens in offensive reactions are considered and particular attention is given to the use of electron paramagnetic resonance (EPR) spectroscopy for the direct observation of such free radical reactions.

Quantitative Electron Paramagnetic Resonance: The Importance of Matching the Q-Factor of Standards and Samples

2001 ◽  
Vol 55 (10) ◽  
pp. 1375-1381 ◽  
Author(s):  
Richard L. Blakley ◽  
Dwight D. Henry ◽  
Walter T. Morgan ◽  
William L. Clapp ◽  
Carr J. Smith ◽  
...  
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Free Radicals ◽  
Free Radical ◽  
Spin Trapping ◽  
Microwave Energy ◽  
Q Factor ◽  
Paramagnetic Resonance ◽  
Tert Butyl ◽  
Electron Paramagnetic ◽  
Stable Free Radicals

Electron paramagnetic resonance (EPR) quantification of free radicals from different samples facilitates comparison of free radical concentrations. Stable free radicals, such as 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), in a suitable solvent (e.g., benzene) can be used as a quantification standard. Free radicals found in samples can be shorter lived than radicals in prepared standards and require stabilizing spin-trapping agents such as N-tert-butyl-α-phenylnitrone (PBN) in an appropriate solvent (e.g., benzene). Analysis in our laboratory showed that free radicals from spin-trapped samples quantified against a standard of TEMPO in benzene displayed large differences among identical samples measured on either a Micro-Now 8300, Micro-Now 8400, or Bruker EMX EPR instrument. The Bruker instrument reported that the typical TEMPO in benzene standard had a Q-factor of ∼4400 while the Q-factor of our PBN-containing samples was ∼2500. (The Q-factor is inversely proportional to the amount of dissipated microwave energy in an EPR cavity.) By placing the TEMPO standard in a PBN/benzene solvent matrix we were able to match the Q-factor of our standards and samples, resulting in each of the three EPR instruments giving the same quantified free radical yields for the samples. This result points out the importance of matching the Q-factor between samples and standards for any quantitative EPR measurement.

Changes in free radical profiles during the callogenesis of responsive and recalcitrant potato genotypes

1994 ◽  
Vol 102 ◽  
pp. 243-246 ◽  
Author(s):  
E. Bailey ◽  
N. Deighton ◽  
S. A. Clulow ◽  
B. A. Goodman ◽  
E. E. Benson
Keyword(s):  
Free Radicals ◽  
Free Radical ◽  
Plant Tissue ◽  
Direct Evidence ◽  
Paramagnetic Resonance ◽  
Biochemical Basis ◽  
Plant Tissue Cultures ◽  
Electron Paramagnetic ◽  
Free Radical Activity

Changes of the in vitro morphogenetic state may be achieved for some potato genotypes, but others are unresponsive (recalcitrant). Although the biochemical basis for somatic recalcitrance is unknown, evidence suggests that two different aspects of oxidative stress may be involved. Phenolic oxidation is a major problem in manipulating cultures of woody plant species (Thorpe & Harry 1990) and lipid peroxidation has been associated with recalcitrance in monocotyledonous plants (Cutler et al. 1989; Benson et al. 1992). Both oxidative phenomena are believed to be free-radical mediated, but to date there is no reported direct evidence for the formation of free radicals during plant tissue culture callogenesis. The objectives of the present study were twofold; to assess the feasibility of using electron paramagnetic resonance (EPR) spectroscopy to detect free radicals directly in plant tissue cultures and to investigate free radical activity during dedifferentiation of responsive and unresponsive potato genotypes.

scholarly journals Effect of UV Irradiation and Temperature on Free Radical Properties in Dehydrocholic and Ursodeoxycholic Acids: An EPR Study

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Małgorzata Dołowy ◽  
Paweł Ramos ◽  
Barbara Pilawa
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Free Radicals ◽  
Bile Acid ◽  
Free Radical ◽  
Bile Acids ◽  
Uv Irradiation ◽  
Thermal Method ◽  
Paramagnetic Resonance ◽  
Thermal Sterilization ◽  
Electron Paramagnetic

The effect of UV irradiation and temperature on the formation and properties of free radicals in two pharmaceutical important bile acids, such as dehydrocholic (DH) and ursodeoxycholic acids (UDC), was examined. Electron paramagnetic resonance (EPR) spectroscopy was applied to determine the paramagnetic character of UV irradiated and thermally sterilized drugs. Thermal and UV irradiation sterilizations of both compounds were carried out at different conditions according to pharmaceutical norms. The performed EPR measurements of UV irradiated and thermally sterilized DH and UDC samples proved the existence of the complex free radical systems in examined bile acids. Significant influence of UV irradiation in comparison with applied thermal sterilization on free radical concentrations in DH and UDC samples was observed. The results pointed out that thermal method is most suitable for bile acid sterilization. Therefore, this kind of sterilization should be applied in practice.

Observations on the in situ detection of free radicals in leaves using electron paramagnetic resonance spectrometry

1992 ◽  
Vol 70 (1) ◽  
pp. 192-199 ◽  
Author(s):  
Victor C. Runeckles ◽  
Manivalde Vaartnou
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Free Radicals ◽  
Free Radical ◽  
Poa Pratensis ◽  
Leaf Tissue ◽  
Paramagnetic Resonance ◽  
Electron Paramagnetic Resonance Spectrometry ◽  
Intact Leaf ◽  
Electron Paramagnetic

To follow in situ changes in free radicals in leaves subjected to changes in the composition of the surrounding air, a system has been developed for obtaining X-band (9 GHz) electron paramagnetic resonance (EPR) spectra of intact leaf tissue over extended periods. Studies with radish (Raphanus sativus), bluegrass (Poa pratensis), and ryegrass (Lolium perenne) leaves in darkness or illuminated with 650 nm, 710 nm, or white light in the spectrometer cavity readily reveal the photosynthetic signals I and II, and signals attributable to Mn2+ and Fe3+. Detached pieces of leaf cannot be used after about 1 h in the cavity because of the appearance of a large EPR signal resulting from excision. However, attached leaves of the grasses can be maintained in a fully functioning state in the cavity for several days, or can be withdrawn and replaced at will. Plants grown in high photon influx densities were found to reveal a large free radical signal, related to photoinhibition, that masks the typical photosynthetic signals but that can usually be eliminated by subjecting the tissue to 9 GHz microwave radiation. Signal changes in response to changes in the composition of the air stream can be directly tracked over extended periods, provided that no major changes occur in the underlying Mn2+ or Fe3+ signals. Preliminary studies with the air pollutants, sulphur dioxide, and ozone have demonstrated the potential of the system for revealing changes in the photosynthetic and other EPR signals resulting from the uptake of such phytotoxic gases. Key words: free radical, electron paramagnetic resonance spectrometry, intact leaf tissue, photosystem, air pollution, stress.

Electron paramagnetic resonance spectroscopy of stable free radicals in the liver compared with ultrastructural and functional damage in a rat model of alcohol- and iron-overload

1993 ◽  
Vol 84 (3) ◽  
pp. 339-348 ◽  
Author(s):  
Graham P. Butcher ◽  
Nigel Deighton ◽  
Roger M. Batt ◽  
Boliang Ding ◽  
Susan Haywood ◽  
...  
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Free Radicals ◽  
Free Radical ◽  
Iron Overload ◽  
Electron Paramagnetic Resonance Spectroscopy ◽  
Resonance Spectroscopy ◽  
Paramagnetic Resonance ◽  
Significant Difference ◽  
Electron Paramagnetic ◽  
Radical Signal

1. Electron paramagnetic resonance spectroscopy was used to study free-radical signals in freeze-clamped frozen liver tissue from rats after a 1 year period of dietary supplementation with alcohol, iron, or alcohol and iron. In alcohol-fed, iron-fed and alcohol- and iron-fed animals, mild histological damage was seen on light microscopy and evidence of mitochondrial and nuclear injury was identified by electron microscopy. 2. Subcellular fractionation studies showed an increase in the activity of the peroxisomal marker catalase (P <0.01) in alcohol-fed rats compared with controls, but a fall of 82% (P <0.001) in alcohol- and iron-fed animals. The activity of the mitochondrial marker succinate dehydrogenase rose by 7% (not significant) in alcohol-fed animals and by 17% (not significant) in iron-fed animals, but fell by 94% (P <0.001) in alcohol- and iron-fed animals, suggesting serious impairment of mitochondrial function. 3. Iron overload was substantial in the iron-fed animals and there was an excellent correlation between liver iron concentration and iron-derived signals by electron paramagnetic resonance spectroscopy (P <0.001). A clear free-radical signal of g = 2.003–2.005 was detected in all liver samples, but there was no significant difference in the magnitude of this signal in any study group. 4. The absence of any increase in the stable free-radical signal, even in the presence of considerable hepatic damage, does not support the hypothesis that free radicals mediate alcoholic liver disease in this animal model, although the results cannot be taken as proof against this hypothesis.

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