Roots of 10- and 14-day-old seedlings and excised leaves of cotton (Gossypium hirsutum L. ‘Coker 310’), jimsonweed (Datura stramonium L.), peanuts (Arachis hypogaea L. ‘Florigiant’), and prickly sida (Sida spinosa L.) were treated with ring-labeled 14C-tetrafluron {N,N-dimethyl-N′-[3-(1,1,2,2-tetrafluoroethoxy)phenyl] urea} in liquid culture. Herbicide absorption and subsequent translocation were limited in peanuts, intermediate in cotton, and very high in jimsonweed and prickly sida. Absorption of 14C-tetrafluron increased with time in 10- and 14-day-old seedlings. After 6 h, 10-day-old jimsonweed had absorbed as much as 50% of the initial 10-μg dose, whereas peanuts absorbed only 10%. Almost 100% uptake was observed after 48 h with 14-day-old seedlings of jimsonweed and prickly sida. Methanol-extracted 14C increased with time, and was higher for the weeds than for the crops. Only a small fraction of methanol-insoluble radioactive material was obtained, with the largest value in 14-day-old cotton at 48 h (3.0%). Autoradiographs demonstrated more rapid translocation of radioactivity from roots to shoots in jimsonweed and prickly sida than in cotton and peanuts. Limited absorption and translocation of tetrafluron in seedlings of peanut and cotton, and the rapid absorption and subsequent accumulation of high concentrations in seedlings of jimsonweed and prickly sida, are proposed to explain the selective action observed.
