PERTANIKA JOURNAL OF TROPICAL AGRICULTURAL SCIENCE

The mechanism of paraquat resistance in Crassocephalum crepidioides at the six-leaf stage was investigated. The extractable paraquat was not metabolized by the leaf tissue in the resistant (R) and susceptible (S) biotypes. Therefore, differential metabolism does not appear to play a role in the mechanism of resistance. The S biotype absorbed 44% more 14C-paraquat than the R biotype. However, more than 98% of the absorbed 14C-paraquat remained on the treated leaf of both biotypes. The difference in absorption had a negative correlation with the amount of epicuticular wax as well as the cuticle of leaf surfaces in both biotypes. The results of this study suggest that differential absorption may be a factor that accounts for resistance to paraquat at the six-leaf stage.