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1991 (2)
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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 DEBUG INFO      
 TEI-XML for    default:Reihe_C/46/ZNC-1991-46c-0957.pdf 
 Identifier    ZNC-1991-46c-0957 
 Volume    46