Protoporphyrin Accumulation Induced by Peroxidizing Herbicides is Counteracted by Safeners

Peter Böger and Roswitha M iller Lehrstuhl für Physiologie und Biochemie der Pflanzen, Universität Konstanz, D-78434 Konstanz, Bundesrepublik Deutschland Z. Naturforsch. 49c, 775-780 (1994); received October 13, 1994 Peroxidizing Herbicides, Safeners, Protoporphyrin IX Accumulation, Protoporphyrinogen Oxidase, Mixed Function Oxidase A number of safeners like naphthalene-1,8-dicarboxylic acid anhydride (naphthalic anhy­ dride) or dichloroacetyl-hexahydro-3,3,8-a-trimethylpyrrolo-[l ,2 a]-pyrimidine-6-(2 H)-one (BAS 145138) drastically decreased the accumulation of protoporphyrin IX induced by a peroxidative cyclic imide (chlorophthalim, N-(4-chlorophenyl)-3,4,5,6-tetrahydrophthalimide), or p-nitrodiphenyl ether (acifluorfen methyl, 5-[2-chloro-4-(trifluoromethyl)phenoxy]2-nitrobenzoicmethylester). This effect was observed with etiolated maize and cress seedlings during a 16-h illumination period with these herbicides and 0.1 to 1 mM safener present. The safeners did not affect the inhibition of protoporphyrinogen oxidase, the target enzyme of peroxidative herbicides. Mixed function oxidase inhibitors did not influence this safening effect. A microsome preparation from safener-treated maize seedlings did neither degrade protoporphyrin IX nor protoporphyrinogen IX.