Translocation and Degradation of Bromoxynil in a Resistant and a Susceptible Species

Abstract

The relation of translocation and degradation to selectivity of 3,5-dibromo-4-hydroxybenzonitrile (bromoxynil) in winter wheat (Triticum aestivum L., var. Nugaines), a resistant species, and coast fiddleneck (Amsinckia intermedia Fisch. & Mey.), a susceptible species, was examined. Radioautographic and extraction analysis revealed that the label from 14C-bromoxynil was more mobile in coast fiddleneck than in wheat. Higher levels of soluble radioactivity were found in extracts of coast fiddleneck than wheat. Higher levels of insoluble label were found in tissue residues of wheat than coast fiddleneck. In both species, most of the activity remained in treated leaves. A high percentage of the soluble activity was attributed to 14C-bromoxynil in both wheat and coast fiddleneck. The evolution of 14CO2 by wheat treated with 14C-bromoxynil significantly exceeded that of coast fiddleneck. The difference in susceptibility between winter wheat and coast fiddleneck appears to be explained partly by differential translocation and degradation of bromoxynil.