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'Herbicides' in keywords Facet   Publication Year 1991  [X]
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1Author    Zsigmond Ekler, FerencD. UtkaRequires cookie*
 Title    Chemical Reactivity and Safener Activity of Acetal Compounds  
 Abstract    Although detailed examinations have been published on structure-activity relationships of herbicide safeners, only a few data are available on chemical reactivity-safener activity rela­ tionships. Chemical reactivity o f acetamide type compounds as well as their safener activity against thiocarbamate herbicides change with the number o f chlorine substituents in the order: non-chlorinated < monochloro < dichloro. Several compounds of another chemical group, acetals (e.g. MG-191, 2-dichloromethyl-2-methyl-l,3-dioxolane), are also effective safeners for thiocarbamate herbicides. According to our growth room studies, the safener activity o f ace­ tals also increases with increasing chlorine content up to two chlorine atoms on the same car­ bon. A number of differently chlorinated acetals have been synthesized and their acid-cata­ lyzed hydrolysis rate determined in order to establish a relationship between their bioactivity and chemical reactivity. The hydrolysis rate order of acetals containing no, one or two chlorine atoms: non-chlorinated > monochloro > dichloro, is just the opposite than what has been found for acetamides. Thus, safener activity of acetals increases with decreasing chemical reac­ tivity. The opposite reactivity order of acetamides and acetals can be explained by the different mechanisms of their hydrolysis. Dichloroacetals may not be effective safeners in their original structure. In plants, however, they can be biologically activated to active safeners by a trans­ formation other than hydrolysis. 
  Reference    Z. Naturforsch. 46c, 810—814 (1991); received March 26 1991 
  Published    1991 
  Keywords    Acetals, Hydrolysis, Herbicides, Herbicide Safeners, Zea mays (L) 
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 TEI-XML for    default:Reihe_C/46/ZNC-1991-46c-0810.pdf 
 Identifier    ZNC-1991-46c-0810 
 Volume    46 
2Author    J.Dirk Naber, JackJ S Van RensenRequires cookie*
 Title    Activity of Photosystem II Herbicides Is Related with Their Residence Times at the D 1 Protein  
 Abstract    The reversible binding kinetics o f atrazine, diuron and ioxynil were measured via their bind­ ing and release parameters during steady state inhibition o f electron transport. The parameters were determined in isolated chloroplasts o f peas and o f triazine-resistant and -susceptible bio­ types o f Chenopodium album using a kinetic model. This model is based on the flash-induced oxygen evolution patterns o f isolated broken chloroplasts. It was found that the binding parameters were always significantly higher in the case o f an oxidized acceptor quinone complex as compared with a semi-reduced complex. Triazine resist­ ance seems to originate from a significant increase o f the release kinetics. The release parame­ ters could be used to calculate the residence times o f the herbicides at the D 1 protein. The values o f these residence times were always much higher for the herbicides than for Q B; this explains the inhibition o f electron transport. The only exception was the residence time o f atra­ zine in the resistant biotype, where the value was close to that o f Q B. It is concluded that the "on" kinetics o f a com pound to its binding environment at the D 1 protein are determined principally by the accessibility o f the niche to the com pound. The dif­ ferences in activity between herbicides are mainly due to variations in the release kinetics. 
  Reference    Z. Naturforsch. 46c, 575—5 (1991); received March 18 1991 
  Published    1991 
  Keywords    Chloroplasts, Photosystem II, D 1 Protein, Herbicides, Triazine Resistance 
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 TEI-XML for    default:Reihe_C/46/ZNC-1991-46c-0575.pdf 
 Identifier    ZNC-1991-46c-0575 
 Volume    46