Mode of action of dipyridyl quaternary salts as herbicides

Homer, R. F.; Mees, G. C.; Tomlinson, T. E.

doi:10.1002/jsfa.2740110604

Cited by 143 publications

(40 citation statements)

References 11 publications

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“…PQ+-+ 02-PQ2 + *°2 (1) In 1960, Homer and others (6) proposed that the reduction of paraquat to its free radical was an essential step in its herbicidal mode of action, because a correlation was found between the reduction potential of paraquat analogs and their herbicidal activity (6). Paraquat is reduced to its free radical within chloroplasts during photosynthesis, and the herbicidal activity of I + I+ ehu H &I paraquat requires light for electron transport.…”

Section: Paraquat and Other Bipyridylium Compoundsmentioning

confidence: 99%

Redox cycling of radical anion metabolites of toxic chemicals and drugs and the Marcus theory of electron transfer.

Mason

1990

Environ Health Perspect

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A wide variety of aromatic compounds are enzymatically reduced to form anion free radicals that generally contain one more electron than their parent compounds. In general, the electron donor is any of a wide variety of flavoenzymes. Once formed, these anion free radicals reduce molecular oxygen to superoxide and regenerate the parent compound unchanged. The net reaction is the oxidation of the flavoenzyme's coenzymes and the reduction of molecular oxygen. This catalytic behavior has been described as futile metabolism or redox cycling. Electron transfer theory is being applied to these reactions and, in some cases, has successfully correlated V., and Km with the reduction potentials of the aromatic compounds.

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Section: Paraquat and Other Bipyridylium Compoundsmentioning

confidence: 99%

Redox cycling of radical anion metabolites of toxic chemicals and drugs and the Marcus theory of electron transfer.

Mason

1990

Environ Health Perspect

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“…(27). (c) Methylviologen is known to stimulate the production of O- (5,25). The addition of methylviologen caused the inhibitory effect on the photosynthetic CO2 fixation (Fig.…”

Section: Resultsmentioning

confidence: 96%

“…ascorbate and reduced glutathione), capable of catalytically removing these toxic species (6,24). The addition of methylviologen to green leaf tissue induces a prominent herbicidal effect by enhancing 02-production linked to PSI (4,5,25,32). The photooxidative destruction of the prokaryotic blue-green alga, Anacystis nidulans, is one of the well documented examples of photodynamic action in photoautotrophs (1, 2).…”

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confidence: 99%

Photooxidative Damage in Photosynthetic Activities of Chromatium vinosum

Asami¹,

Akazawa²

1978

Plant Physiol.

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The capacity of photosynthetic CO2 fiXation in the anaerobic purplesulfur bacterium, COmadum vinosum is markedly impaired by strong ilumination (9 x 10i lux) in the presence of 100% 0s. In the absence of HCO0, decline in activity occurred gradually, with about 40% of the initial activity reminng after a 1-hour incubation. The addition of 50 milimolar HCOj-to the incubation medium resulted in a measurable delay (about 30 minutes) of the inactivation process. Ribulose-1,5-bisphosphate carboxylase activty and light-dependent Os uptake (electron flow) or crude extracts prepared after pretreatment of the bacterial cells with 02 and light were not affected but the photophosphorylation capacity of either bacterial cells or chromatophores was drastically reduced. The inhibition of photophosphorylation in the chromatophore preparations was signiflcantiy reduced by the addition of either an Os scavenger, Tiron, or an 102 scavenger, atocopherol. These results suggest that the active O2 species, Os2 or 10, might take part in the observed inactivation.The pretreatment of the bacteria with 02 and light inhibited CO2 assimilation through the Calvin-Benson cycle, while relatively stimulating the formation of aspartate and glutamate. It also inhibited the conversion of glycolate to glycine, resulting in a sustained extraceUlular excretion of glycolate. The inactivation of photosynthetic CO2 fixation by intact cells was enhanced by low temperature, KCN, or methylviologen addition during the pretreatment with 02 and light. The mechanism(s) of 02-dependent photoinactivation of photosynthetic activities in Chromadum are discussed in relation to the possible role of photorespiration as a means of producing CO2 in the photosynthetic system.There are two types of inhibitory effects of 02 on photosynthesis in various photoautotrophic organisms. The first mechanism which is reversible and is often referred to as the Warburg effect is considered to govern photorespiratory processes. It is likely a result of the competitive inhibition of CO2 fixation by 02 (14,15,20,34). We have previously demonstrated an inhibitory effect of 02 on photosynthetic CO2 fixation as well as the mechanism of glycolate biosynthesis and metabolism by the photosynthetic anaerobic bacterium, Chromatium vinosum, which are phenomenologically similar to the Warburg effect observed in higher plants (7,29). The second type of 02 inhibition, which is irreversible and often referred to as the photodynamic action, is caused by photooxidation damage of cellular component(s) (36). A number of isolated enzymes or photosystem(s) in green plants are subject to photooxidative inactivation (12,18,22,26,33). The Chl-bearing photosystems of photosynthetic organisms serve to transform ra-

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“…Its redox properties were investigated by Michaelis and Hill in 1933 [69], and methyl viologen was initially used as a redox indicator due to its intensely colored radical form (see Section 9.2.2) [70]. Only in the middle of the twentieth century was it discovered that methyl viologen acts as a nonspecific contact herbicide [71] and it was subsequently used in agriculture as rapid desiccant of green plant tissue [72]. Its ability to adsorb to soil particles and organic soil matter [73,74] limits the bioavailability for microorganisms and plants [75], and fosters a rapid biological deactivation.…”

Section: Detoxification Of Ros -Antioxidative Network In Plantsmentioning

confidence: 99%