PLASMA-MEMBRANE LIPID-COMPOSITION AND HERBICIDE EFFECTS ON LIPOXYGENASE ACTIVITY DO NOT CONTRIBUTE TO DIFFERENTIAL MEMBRANE RESPONSES IN HERBICIDE-RESISTANT AND HERBICIDE-SUSCEPTIBLE WILD OAT (AVENA-FATUA L) BIOTYPES

Plasma membrane lipid composition of herbicide-resistant (R) and -susc eptible (S) wild oat biotypes was analyzed to determine the basis for the differential effect of diclofop on the transmembrane electrogenic potential between the two biotypes and reduced herbicide uptake into p rotoplasts of the R biotype. In addition, Lipoxygenase (LOX) activity was examined in herbicide-treated and untreated R and S plants to dete rmine its involvement in herbicide action and resistance. Overall, no significant differences in lipid composition were found between the tw o biotypes. Glycolipids represented 41 and 36%, phospholipids 29 and 3 7%, and free sterols 30 and 27% of the total plasma membrane lipid in the R and S biotypes, respectively No differences in LOX activity were observed between the herbicide-treated and untreated wild oat biotype s. It was concluded that differences in membrane transport of diclofop and its effect on plasma membrane potential in the R and S biotypes a re not related to differences in membrane lipid composition or to diff erential effects of herbicides on LOX activity in the two biotypes.