Mode imidazolinones

The inhibitors of amino acid synthesis, sulfonylureas, imidazolinones, and glyphosate, were first recognized as general growth inhibitors that prevent mitotic entry (188,189). Whatever the mode of action, herbicides that inhibit amino acid synthesis also cause a rapid inhibition of cell growth, usually through inhibition of mitotic entry. 

Examples of the application of the three-ion-criteria in SIM mode can be found in reports on the analysis of acidic pesticides [42], sulfonylureas [49-51], and imidazolinone herbicides [51]. Rodriguez and Orescan [51] actually apply... 

Identification of the mode of action of the imidazolinones occurred while resistant cell lines were being isolated. Imidazolinones inhibit acetohydroxyacid synthase (AHAS EC 4.1.3.18), the first enzyme in the pathway of branched chain amino acid synthesis (8). Imidazolinone-resistant cell lines provide proof that inhibition of AHAS is the site of action of the imidazolinones AHAS activities in extracts from resistant corn cell lines are highly resistant to inhibition by imidazolinone herbicides (7). 

With the invention of the aceto-hydoxy-add synthesis inhibitors (AHAS) the dominance of herbiddes that ad as photosynthesis inhibitors was dramatically broken - as it was also by the development of genetically modified herbicide tolerant crops. These especially important areas of research and development, from the 1990s up to now, are exemplified in Chapters 3 and 7. The development of 12 new sulfonyl urea herbicides launched since 1995 and the invention of four development compounds of the same chemical class, after the introduction to the market of twenty compounds already between 1980 and 1995, refleds the importance of this biochemical mode of adion for the herbicide market as well as the different chemistries found to be active at this target, such as imidazolinones, triazolo-pyrimidines, pyrimidinyl-carboxylates, and sulfonylaminocarbonyl-triazolinones. 

All four herbicides belong to completely different chemical classes sethoxydim is a cyclohexanone, fluazif op-butyl a phenoxyphenoxy-type con und, imazaquin an imidazolinone, and chlorimuron-ett l a sulfonylurea. The mode of action of fluazifop-butyl and imazaquin is inhibition of acetyl-CoA carboxylase (ACC) (, 7 ) Obviously, this is reflected by the similarity of the response patterns. The way it corresponds is not a direct one we can say nothing ed>out fatty acid biosynthesis inhibition by looking at the response pattern. What we see is the influence on other meted>olites, which are in most cases only indirectly connected with fatty acid biosynthesis. But the patterns are strikingly similar. 

Imazaquin, an example of the imidazolinone class of herbicides, is particularly selective to soybeans. These compounds have a similar mode of action to that of the sulfonylurea herbicides, which will be discussed later. They block branched chain amino acid biosynthesis by inhibition of the enzyme acetolactate synthase (ALS). 

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