• Korean Journal of Environmental Agriculture
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• v.13 no.3
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• pp.373-385
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• 1994

Resistance to paraquat (1,1'-dimethyl-4,4'-bipyridilium ion) has developed in 12 species of 8 genera to which paraquat has been applied 6 to 10 times per year for 5 or more years. In recent years, tolerance to paraquat has been found in Rehmannia glutinosa (Gaertn.) Liboch. ex Fisch. & Mey. which has never been applied with any herbicides involving paraquat. In this review, we differentiate the terms, resistance and tolerance, on the basis of the paraquat-exposure history. Five hypotheses have been evaluated in several species as potential mechanisms of paraquat resistance and/or tolerance. In a species, the mode of action may be due to 1) reduced quantities of paraquat absorbed through the leaf surface, 2) detoxification of paraquat caused by the enhanced paraquat-metabolic activity, 3) rapid sequestration reducing level of paraquat at the site of action in chloroplast, 4) alteration of site of action in photosystem I resulting in interruption of electron transport to paraquat, and 5) rapid enzymatic detoxification of superoxide and other toxic forms of oxygen.

• Microbiology and Biotechnology Letters
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• v.28 no.1
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• pp.1-7
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• 2000

The bacterial strain JW-2 which conferred resistance against paraquat (1,1'-dimethyl-4,4'-bipyridinium dichloride) was isolated from soil. The strain was identified as an Ochrobactrum anthropi based on its morphological, physiological, biological and fatty acid composition, and was designated as Ochrobactrum anthropi JW-2. We compard paraquat resistance of O. anthropi JW-2 with Escherichia coli J105. In the presence of 100mM paraquat, E. coli JM105 was not grown whereas the growth rate of O. anthropi was about 70% of control. We compared the sensitivity of O. anthropi JW-2 and E. coli J105 to redox-cycling compounds such as paraquat, plumbagin or menadione, which are known to exacebate wuperoxide generation. O. anthropi JW-2 did not show cross-resistance to plumbagin or menadione. superoxide dismutase activity was increased in paraqunt-treated E. coli JM105 while it was not increased in O.anthropi JW-2. These results suggest that the mechanism of paraquat resistance in O.anthropi JW-2 is probably due to selectively decreased permeability toward paraquat by membrane protein.

• Korean Journal of Weed Science
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• v.15 no.1
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• pp.1-12
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• 1995

These researches have been conducted to obtain the basic information of the effects of paraquat on plant species and to screen the plant species showing specific responses to paraquat. Paraquat resistance related to ecotype and overwintering capacity. Perennial and biennial species showed higher resistance than annual species. In a family, most species showed higher resistance were overwintering species. Lamiaceae, Brassicaceae, and Caryophyllaceae were tolerant to paraquat, whereas Poaceae and Asteraceae were sensitive. Especially Mosla dianthera of Lamiaceae, Hemistepta lyrata and Aster pilosus of Asteraceae, and Paspalum thunbergii of Poaceae showed higher tolerance than others. The response patterns of plant species on germination stage were different to those on vegetative stage. Germination of Amarathus lividus, Arabis glabra, and Bidens frondosa was not inhibited by paraquat. But their seedling growth were highly inhibited.

• Applied Biological Chemistry
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• v.43 no.1
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• pp.46-51
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• 2000

The resistance of Cornyza bonariensis to herbicide paraquat was investigated by evaluating the activities of three enzymes concerning in scavenging paraquat-generated toxic oxygen species such as superoxide radical and hydrogen peroxide in resistant and susceptible biotypes. Conyza bonariensis inhabited in cultivated area was more tolerant to paraquat than that of uncultivated area. This is the first report that a biotype of Cornyza bonariensis has appeared in an area with repeated paraquat treatments of Korea. Superoxide dismutase activity of resistant biotype was 20% higher as 150 than that of susceptible biotype. Ascorbate peroxidase activity of resistant biotype was 44% higher than that of susceptible biotype. Glutathione reductase activity of resistant biotype was 64% higher than that of susceptible biotype. It can be concluded from above results that the resistance of Conyza bonariensis to paraquat depends partially on the toxic oxygen species-scavenging efficiency of protective multienzymatic system which is composed of three enzymes, superoxide dismutase, ascorbate peroxidase, and glutathione reductase.

• Weed & Turfgrass Science
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• v.2 no.3
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• pp.254-259
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• 2013

The mechanisms of resistance to oxyfluorfen (OF) and paraquat (PQ) were investigated in rice plants. Examination of the concentration dependence of oxyfluorfen- or paraquat-induced increase in conductivity showed that conductivities in the OF- and PQ-treated leaf squares were increased with 0.1 ${\mu}M$ oxyfluorfen and 0.01 ${\mu}M$ paraquat and further increased with higher concentrations. The levels of conductivity were approximately 10-times higher in the PQ-treated plants than in the OF-treated plants, indicating that the PQ-treated plants suffered more severe photodynamic damage than the OF-treated plants. The photooxidative stress caused by foliar application of either 50 ${\mu}M$ oxyfluorfen or 100 ${\mu}M$ paraquat increased the enzyme activities of ascorbate peroxidase and peroxidase 1 day after the herbicide treatments and then further increased their enzyme activities 2 days after the treatments. The activities of catalase began to increase 2 days after the oxyfluorfen and paraquat treatments. These antioxidant enzymes appear to play an essential part of defense mechanisms against oxyfluorfen and paraquat. Our results demonstrate that paraquat caused more severe oxidative stress, as indicated by a greater change in conductivity, thereby resulting in greater increases in antioxidant responses in plants, compared with those of oxyfluorfen.

• Korean Journal of Weed Science
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• v.12 no.4
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• pp.374-379
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• 1992

Response of medicinal plants(58 species in 28 families) cultivated or naturally grown in Korea on paraquat (1,1'-dimethyl-4,4'-bipyridinium ion) was determined. All the plants, except for Jiwhang(Rehmannia glutinosa Liboch.) were killed by paraquat at 0. 8kg $ha^{-1}$. Jiwhang showed a great resistance to paraquat. The phytotoxic effect did not occur in Jiwhang with paraquat applied at 3.2kg $ha^{-1}$. Only 10% growth inhibition of Jiwhang was obtained at 4.8kg $ha^{-1}$. Normal growth of Jiwhang also occurred when at 0.8kg $ha^{-1}$ of paraquat different application dates from 2 leaf stage(LS) to 8 LS and/or five-repeated applications at 20-day intervals starting from 3 LS were employed. However, Jiwhang was completely killed by glyphosate[N-(phosphonomethyl) glycine], 2,4-D[2,4-dichlorophenoxy) acetic acid], and dicamba[3,6-dichloro-2-methoxy benzoic acid]+2, 4-D at the respective recommended rates.

• Korean Journal of Weed Science
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• v.6 no.2
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• pp.191-200
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• 1986

The study was conducted to screen paraquat-tolerant plant species among crops and weeds, using the response of plant like leaf disc discoloration, visual injury and dry weight in the presence of paraquat. Mechanism of paraquat-tolerance was investigated in strains of soybean through evaluating activities of superoxide dismutase and peroxidase and the multiplication of callus derived from soybean cotyledon. In crops, Kwanggyo has been selected as a paraquat-tolerant variety among soybean cultivars tested, and Hood as a susceptible one. In weeds, Polygonum aviculare, Chenopodium album and Pinellia ternata were evaluated as the paraquat resistant species, providing the possibility for the donor plant species for paraquat resistance. Activity of superoxide dismutase known to detoxify paraquat was markedly greater in Kwanggyo, a paraquat-tolerant cultivar than in Hood, a susceptible one. In addition, the similar response like superoxide dismutase was observed in peroxidese activity. The greater inhibition of callus multiplication was determined in Hood, a susceptible one than a tolerant one, Kwnggyo. Based on all the informations, it is strongly proposed that paraquat tolerance in soybean is due to destruction of $O_2^-$ by elevated concentration of superoxide dismutase in the tolerant cultivar.

• Korean Journal of Veterinary Research
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• v.34 no.2
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• pp.339-347
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• 1994

This study was carried out to investigate the pathological changes with paraquat(1.1'-dimethyl-4.4'-dipyrildiylium dichloride) administered by intraperitoneally, orally, skin applied in mice, rats and rabbits. Results were obtained as follows; In 2 days after paraquat administration clinical signs anorexia, depression, tachypnea, and tachycardia, respiratory failure, coma and death were observed in mice, rats and rabbits. Compared toxicity of paraquat with mouse were observed toward to paraquat that resistance was strong than rats and rabbits. Also, mortality of skin application were found the low than intraperitoneal and high than oral administration. In the case of gross observation were appear lips moisture in orally administered rats and rabbits by skin application. Lung of all laboratory animals were observed congestion and haemorrhage, swelling or atrophy. In the case of microscopic findings were severe congestion and haemorrhage, interstitial pneumonia of lung. Congestion and haemorrhage of liver, congestion and haemorrhage, renal tubule epithelium necrosis of kidney were observed in mice, rats and rabbits. Skin application group of mice, rats and rabbits showed infiltration of inflammatory cells and folliculitis of epidermis and dermis. Also, in oral administration group showed congestion and haemorrhage, tachment, necrosis of alimentary tract mucosa.

• Microbiology and Biotechnology Letters
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• v.34 no.1
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• pp.15-22
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• 2006

A 4,971 bp chromosomal DNA fragment containing the pqrA, paraquat resistance gene, was cloned from Ochrobactrum anthropi JW-2, and the complete nucleotide sequence was determined. Nucleotide and deduced amino acid sequences of the fragment revealed the presence of 4 complete ORFs (orf2, pqrA, orf3, orf4) and two incomplete ORFs(orf1, orf5). Orf1, pqrA, orf4 and orf5 exists at the direct strand but orf2 and orf3 exists at the reverse complementary strand. Orf1 which of incomplete sequences without start codon shares homology with ATP binding region of the response regulator receiver. Orf2 shares high homology with members of the tetR family of transcriptional repressor which have a helix-turn-helix (H-T-H) motif. Therefore, the orf2 is predicted as a transcriptional repressor of pqrA and is designated as pqrR2. Orf3 shares high homology with the members of the lysR family acting as a transcriptional activator which have both of a H-T-H motif at the N-terminal region and substrate binding domain at the C-terminal region. Therefore, the orf3 is predicted as a transcriptional activator of pqrA and is designated as pqrR1. Orf4 shows homology with the periplasmic substrate-binding protein of amino acid ABC transporter. Orf5 which of incomplete sequences without stop codon revealed the homology with the permeases protein of amino acid ABC transporter.

• The Korean Journal of Pesticide Science
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• v.9 no.1
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• pp.88-96
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• 2005

Paraquat-resistant biotype of Conyza canadensis (L.) Cronq. was determined by chlorophyll loss and random amplified polymorphic DNA (RAPD) analysis and the resistant mechanism was investigated with respect to absorption, translocation, and binding constant. RAPD analysis for paraquat resistant (R) and susceptible (S) biotypes found in a pear orchard revealed that the biotypes possessed remote genetic relationship. Chlorophyll loss, as an indication of paraquat toxicity, of S biotype was 7.8-fold greater than that of R biotype. There were no differences in contents of epicuticular wax and cuticle and amounts of [14C]paraquat penetrating the cuticle between the two biotypes. Little translocation of the herbicide out of the treated leaf was observed in either biotype. Binding constants of paraquat to the cell wall and thylakoid membrane were 7.4-fold and 16.9-fold, respectively, higher in R biotype than in S biotype. The results suggest that the resistance mechanism of C. canadensis biotype is due partly to high binding affinity of paraquat to the cell wall and thylakoid membrane.