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1991 (5)
1990 (1)
1Author    Carl Fedtke, Bayer Ag, Geschäftsbereich Pflanzenschutz, Entwicklung/. HerbizideRequires cookie*
 Title    Antagonistic Interactions of Mefenacet with Inhibitors of Monooxygenases  
 Abstract    The monooxygenase suicide inhibitor piperonyl butoxide (PBO) antagonizes the inhibitory activity of the herbicide mefenacet in a root regeneration test system with etiolated cut oat stems. When studying the behaviour of [l4C]mefenacet [2-(2-benzothiazolyloxy)-N-methyl-N-phenylacetamide] in cut oat stems that had been pretreated with PBO for 24 h after cutting, an increased rate of uptake and increased concentrations of mefenacet in the tissue were found after PBO as compared to water pretreatment. Increased uptake rates and increased rates of metabolism after PBO pretreatment, supposedly by increased monooxygenation, were also observed with the substrates diuron, 2,4-D and cinnamic acid. Mefenacet induced the same responses as PBO in all systems. The similar actions of mefenacet and PBO are interpreted to suggest that mefenacet might interfere with monooxygenase enzymes. Similar responses, i.e. stimulation of m onooxygena­ tion o f suitable substrates, have been reported for herbicide safeners. An environm entally con­ trolled regulatory response system is suggested to be triggered by the different classes of com­ pounds, mefenacet and similar herbicides, monooxygenase inhibitors, and safeners, and to re­ spond with increased enzyme activities in the monooxygenase and glutathione detoxification pathways. 
  Reference    Z. Naturforsch. 46c, 915—919 (1991); received March 26 1991 
  Published    1991 
  Keywords    Mefenacet, Monooxygenase, Safener, Antagonism, Induction 
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 TEI-XML for    default:Reihe_C/46/ZNC-1991-46c-0915.pdf 
 Identifier    ZNC-1991-46c-0915 
 Volume    46 
2Author    J.Christopher Hall, M. Ira SoniRequires cookie*
 Title    Antagonism by Clopyralid of Picloram-Induced Ethylene Biosynthesis in Rapeseed Plants  
 Abstract    The effect o f clopyralid pretreatment (500 g/ha) on picloram-induced ethylene, ACC (1-am inocyclopropane-l-carboxylic acid), and M ACC [l-(m alonylam ino)-cyclopropane-1-carboxylic acid] was measured in rapeseed plants that were treated with 50 or 100 g/ha o f picloram. In contrast to plants that did not receive a clopyralid pretreatment, ethylene biosyn­ thesis was significantly reduced in plants pretreated with clopyralid prior to picloram. Piclo­ ram-induced levels o f ACC also were significantly reduced in plants receiving pretreatment with clopyralid. In contrast, there was no difference between the levels o f M ACC in plants that were and were not pretreated with clopyralid. Therefore, the mechanism by which clopyralid pretreatment interferes with picloram-induced synthesis o f both ACC and ethylene may be manifested through the blocking o f de novo synthesis o f ACC synthase normally stimulated by picloram. The lack o f significant difference in M ACC levels between plants that were and were not pretreated with clopyralid precludes the stimulation o f enhanced ACC conversion to MACC as an exclusive mechanism o f clopyralid's antidoting activity. It is likely that the rate o f picloram-induced ACC synthesis by plants receiving pretreatment is within their capacity to convert ACC to M ACC, thereby limiting the substrate available for conversion to ethylene. In contrast, it appears that the extent o f ACC synthesis by plants receiving no pretreatment su­ persedes their capacity for conversion to M ACC. thereby resulting in greatly enhanced rates o f ethylene evolution and subsequent developm ent o f injury symptoms. 
  Reference    Z. Naturforsch. 46c, 957 (1991); received January 30 1991 
  Published    1991 
  Keywords    Clopyralid, Picloram, Ethylene, Antagonism, Safener 
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 TEI-XML for    default:Reihe_C/46/ZNC-1991-46c-0957.pdf 
 Identifier    ZNC-1991-46c-0957 
 Volume    46 
3Author    Carl Fedtke, RobertH. Strang, Bayer Ag, Geschäftsbereich Pflanzenschutz, Biologische Anwendungstechnik, ForschungRequires cookie*
 Title    Synergistic Activity of the Herbicide Safener Dichlormid with Herbicides Affecting Photosynthesis  
 Abstract    Dichlormid, a safener for thiolcarbamate herbicides, was tank-mixed with several herbicidal inhibitors of photosystem II, or with the herbicide acifluorfen, and applied postemergence to Ipomoea hederacea plants. Dichlormid had no visible effects on the plants when applied alone, but interacted synergistically with the herbicides in the combination treatments. Dichlormid strongly decreased the ascorbic acid levels in the Ipom oea hederacea cotyledons. Ascorbate is known to protect plant tissue from photooxidative damage. The herbicides which interacted synergistically with dichlormid are believed to generate their phytotoxic action via the produc­ tion of excess singlet oxygen. It is suggested that the decreased ascorbate levels in the Ipomoea hederacea cotyledons after dichlormid treatment result in an impaired singlet oxygen scaveng­ ing system and consequently lead to increased plant damage in the presence of singlet oxygen generating herbicides. 
  Reference    Z. Naturforsch. 45c, 565—567 (1990); received October 13 1989 
  Published    1990 
  Keywords    Herbicide, Synergism, Safener, Oxygen Toxicity, Ascorbic Acid 
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 TEI-XML for    default:Reihe_C/45/ZNC-1990-45c-0565.pdf 
 Identifier    ZNC-1990-45c-0565 
 Volume    45 
4Author    Klaus Kreuz, John Gaudin, Jürg Stingelin, Edith EbertRequires cookie*
 Title    Metabolism of the Aryloxyphenoxypropanoate Herbicide, CGA 184927, in Wheat, Barley and Maize: Differential Effects of the Safener, CGA 185072  
 Abstract    The influence o f the safener, CGA 185072 (5-chloro-8-quinolinoxy-acetic acid-l-methyl-hexyl-ester), on the metabolism of the aryloxyphenoxypropanoate herbicide, CGA 184927 (2-propynyl-/?-2-[4-(5-chloro-3-fluoro-2-pyridinyloxy)-phenoxy]-propionate), was studied in excised leaves of wheat, barley, and maize. In wheat and barley, CGA 184927 readily under­ went ester hydrolysis followed by hydroxylation at the pyridinyl moiety as well as ether cleav­ age between the pyridinyl and the phenyl ring. Ether cleavage constituted the minor pathway in both species. All metabolites were subject to glycosyl conjugation. Tetcyclacis strongly in­ hibited pyridinyl-ring hydroxylation in wheat. M etabolism by hydroxylation and ether cleav­ age was more rapid in wheat than in barley, and was found to be accelerated in the presence of the safener CGA 185072 in both wheat and, to a lesser degree, in barley. Moreover, the safener increased the capacity for O-glycoside form ation in wheat as suggested from studies using the ,4C-labelled pyridinyl-ring hydroxylated metabolite as a precursor. In maize, which is highly susceptible to CGA 184927, rapid ester hydrolysis of CGA 184927 and partial conversion of the corresponding carboxylic acid to glycosyl ester conjugate(s) occurred. However, no further transform ation of the herbicide was found in maize, both in the absence or presence of CGA 185072. It is concluded that the ability o f CGA 185072 to protect wheat from injury by the herbicide, CGA 184927, and to confer partial protection to barley, is related to the ability of the safener to stimulate herbicide metabolism in these crop species. 
  Reference    Z. Naturforsch. 46c, 901—9 (1991); received M arch 26 1991 
  Published    1991 
  Keywords    Aryloxyphenoxypropanoate Herbicide, Safener, Herbicide M etabolism, Monocotyledonous Crops, Glycosyl Conjugation 
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 TEI-XML for    default:Reihe_C/46/ZNC-1991-46c-0901.pdf 
 Identifier    ZNC-1991-46c-0901 
 Volume    46 
5Author    Istvan JablonkaiRequires cookie*
 Title    Basis for Differential Chemical Selectivity of MG-191 Safener against Acetochlor and EPTC Injury to Maize  
 Abstract    The influence of MG-191 safener on the uptake, translocation and metabolism of [l4C]acetochlor and [14C]EPTC was studied. The amounts o f absorbed radioactivity by maize seedlings at 3, 6, 24, and 72 h after applications of [l4C]labeled herbicides and [l4C]MG-191 were different. Plants treated with [l4C]acetochlor took up 30-to 50-fold more radiolabel with­ in 72 h than [14C]EPTC-or [14C]MG-191-treated plants. Addition of MG-191 caused only mi­ nor changes in the rate of herbicide absorption. EPTC and MG-191 and/or their metabolites moved quickly acropetally and partitioned equally between root and shoot tissues up to 72 h. The amount of acetochlor and/or its labeled metabolites translocated to shoot tissues was less than 10%. MG-191 practically had no influence on herbicide translocation rates. With all chemicals the amounts of water-soluble and unextractable fractions increased while the ratio of hexane-extractable metabolites decreased with time. TLC analyses of both water-and hex­ ane-soluble metabolites confirmed the fast metabolism o f acetochlor. The acetochlor metabo­ lism took place via GSH conjugation and more polar, non-conjugated metabolites compared to parent molecule were detected in hexane-soluble fraction. MG-191 enhanced acetochlor metabolism by decreasing the portion of non-metabolized acetochlor. EPTC metabolism re­ sulted in water-soluble metabolites having similar chromatographic properties to those of ace­ tochlor. However, there was no safener effect on non-metabolized EPTC content of plants. It appears that MG-191 protects maize against EPTC by enhancing the early rate of conjugation with GSH after initial oxidative metabolism. 
  Reference    Z. Naturforsch. 46c, 836—845 (1991); received March 26 1991 
  Published    1991 
  Keywords    Chemical Selectivity, Safener, MG-191, Acetochlor, EPTC, Uptake, Translocation, Metabo­ lism 
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 TEI-XML for    default:Reihe_C/46/ZNC-1991-46c-0836.pdf 
 Identifier    ZNC-1991-46c-0836 
 Volume    46 
6Author    JohnV. Dean, JohnW. Gronw, MichaelP. AndersonRequires cookie*
 Title    Glutathione S-Transferase Activity in Nontreated and CGA-154281- Treated Maize Shoots  
 Abstract    Fast protein liquid chromatography (anion exchange) was used to separate glutathione S-transferase isozymes in nontreated etiolated maize shoots and those treated with the herbi­ cide safener C G A -154281 4-(dichloroacetyl)-3,4-dihydro-3-methyl-2 H-l ,4-benzoxazine. Non­ treated shoots contained isozymes active with the following substrates: fra/?s-cinnamic acid (1 isozyme), atrazine (3 isozymes), l-chloro-2,4-dinitrobenzene (1 isozyme), metolachlor (2 isozymes) and the sulfoxide derivative of S-ethyl dipropylcarbamothioate (2 isozymes). Pre­ treatment of shoots with the safener C G A -154281 (1 (aM) had no effect on the activity of the isozymes selective for rratts-cinnamic acid and atrazine but increased the activity of the consti-tutively-expressed isozymes that exhibit activity with l-chloro-2,4-dinitrobenzene, metola­ chlor and the sulfoxide derivative of S-ethyl dipropylcarbamothioate. The safener pretreat­ ment also caused the appearance o f one new isozyme active with l-chloro-2,4-dinitrobenzene and one new isozyme active with metolachlor. The results illustrate the complexity of gluta­ thione S-transferase activity in etiolated maize shoots, and the selective enhancement of gluta­ thione S-transferase isozymes by the safener CG A -154281. 
  Reference    Z. Naturforsch. 46c, 850—855 (1991); received March 26 1991 
  Published    1991 
  Keywords    CG A-154281, Safener, Glutathione S-Transferase, Glutathione, Maize 
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 TEI-XML for    default:Reihe_C/46/ZNC-1991-46c-0850.pdf 
 Identifier    ZNC-1991-46c-0850 
 Volume    46