Absorption, Translocation, and Metabolism of Oxyfluorfen in Rice (Oryza sativa) and Barnyardgrass (Echinochloa crus-galli)

The mode of action and selectivity of oxyfluorfen (2-chloro-4-trifluoromethylphenyl-3-ethoxy-4-nitrophenyl ether) was studied in tolerant rice (Oryza sativa L.) and susceptible barnyardgrass (Echinochloa crus-galli L.). Herbicidal activity of foliarapplied oxyfluorfen was light dependent in both species, but little activity was shown even in light when applied to root. In rice 24hrs after application, 14C recovered in water and chloroform washes of the treated leaf was 10 and 13% in light, and 24 and 27% in dark, respectively, while in barnyardgrass 4 and 6% in light and 10 and 13% in dark, respectively. After water and chloroform washes, 14C present in the treated leaf of rice was 77 in light and 49% in dark, and that in barnyardgrass was 90 in light and 77% in dark. The major portion (63 and 64% in rice and in barnyardgrass, respectively) of the foliar applied 14C-oxyfluorfen was intracellularly distributed in microsomal fraction, and the next portion (22 and 21%, respectively) in chloroplast fraction. Translocation of 14C-oxyfluorfen from foliage or root application was very limited at the range of 0.04 to 3.43% in both species. Translocation of the compound from root application was accelerated in the light, while that from foliage application was inhibited in both species. TLC analysis showed that 24hrs after application, almost all of the applied 14C-oxyfluorfen remained as unaltered in both species.