Uptake and metabolic fate of [14C]-2,4-dichlorophenol and [14C]-2,4-dichloroaniline in wheat (Triticum aestivum) and soybean (Glycine max)

The uptake and metabolism of 14C]-2,4-dichlorophenol (DCP) and 14C]-2,4-dichloroaniline (DCA) were investigated in wheat and soybean. Seeds were exposed to a nutrient solution containing 50 microM of one of two radiolabeled compounds, and plant organs were harvested separately after 18 days of growth. In wheat, uptake of 14C]-2,4-DCP was 16.67 +/- 2.65 and 15.50 +/- 2.60% of 14C]-2,4-DCA. In soybean, uptake of 14C]-2,4-DCP was significantly higher than 14C]-2,4-DCA uptake, 38.39 +/- 2.56 and 18.98 +/- 1.64%, respectively. In the case of 14C]-2,4-DCP, the radioactivity absorbed by both species was found mainly associated with roots, whereas 14C]-2,4-DCA and related metabolites were associated with aerial parts, especially in soybean. In wheat, nonextractable residues represented 7.8 and 8.7% of the applied radioactivity in the case of 14C]-2,4-DCP and 14C]-2,4-DCA, respectively. In soybean, nonextractable residues amounted to 11.8 and 5.8% of the total radioactivity for 14C]-2,4-DCP and 14C]-2,4-DCA, respectively. In wheat, nonextractable residues were nearly equivalent to extractable residues for 14C]-2,4-DCP, whereas they were greater for 14C]-2,4-DCA. In soybean, the amount of extractable residues was significantly greater for both chemicals. However, in both species, nonextractable residues were mainly associated with roots. Isolation of soluble residues was next undertaken using excised shoots (wheat) or excised fully expanded leaves including petioles (soybean). Identification of metabolite structures was made by comparison with authentic standards, by enzymatic hydrolyses, and by electrospray ionization-mass spectrometric analyses. Both plant species shared a common metabolism for 14C]-2,4-DCP and 14C]-2,4-DCA since the malonylated glucoside conjugates were found as the final major metabolites.