Effects of the herbicides SC-0224 and glyphosate on the pool levels of free amino acids, soluble protein, and protein synthesis in inflated duckweed were compared. SC-0224 caused larger increases than glyphosate in the pool levels of amino acids; the increases caused by SC-0224 were similar, however, to those caused by trimethylsulfonium iodide (TMS-I). Expressed on a per gram fresh weight basis, none of the treatments changed soluble protein or the incorporation of 14C-leucine into soluble protein. On a per flask basis (allowing for decreased growth in treated flasks), both herbicides and TMS-I decreased soluble protein and 14C-leucine incorporation. Decreases in soluble protein and 14C-leucine incorporation were equal for SC-0224 and TMS-I but larger than for glyphosate. These data indicate that differences in the phytotoxicity of SC-0224 and glyphosate may be due to the action of the trimethylsulfonium portion of the SC-0224 structure.
