ABSORPTION, TRANSLOCATION, AND METABOLISM OF C-14 CLOMAZONE IN SOYBEAN (GLYCINE-MAX) AND 3 AMARANTHUS WEED SPECIES

The patterns of clomazone (2-[(2-chlorophenyl) methyl-4,4-dimethyl-3-isoxazolidinone) absorption, translocation, and metabolism and their contribution to the plant selectivity of this herbicide were studied in tolerant soybean [Glycine max (L.) Merr.] and Amaranthus hybridus and in susceptible A. retroflexus and A. lividus. Differential root absorption appeared to play a significant role in the differential response of these four plant species to clomazone. Absorption of root-applied14C-clomazone was greater by the two sensitive Amaranthus weeds than by the tolerant soybean and A. hybri-dus. Following application of14C-clomazone to roots, most of the absorbed radioactivity was translocated to the leaves of all four species. Approximately 50% of the absorbed14C-clomazone was metabolized by all four plant species as early as 12 h after treatment. Thin layer Chromatographic (TLC) analysis of plant tissue extracts from all four species revealed the formation of two major metabolites of clomazone. These unidentified metabolites had Rf values of 0.4 and 0.8, respectively, in a butanol:acetic acid:water (12:3:5, vol/vol/vol) developing system. The Rf value of unaltered clomazone in this system was 0.95. Differential metabolism or differential rate of metabolism of clomazone was not observed in this study and did not seem to account for the tolerance of soybean and A. hybridus or the suceptibility of A. retroflexus and A. lividus to this herbicide. © 1990 Springer-Verlag New York Inc.