Absorption, translocation, and metabolism of sulfentrazone in potato and selected weed species

Potato exhibits adequate tolerance to preemergence applications of sulfentrazone at rates up to 0.28 kg ai ha^-1. Sulfentrazone also controls several troublesome weeds such as common lambsquarters but may be less effective against jimsonweed. Laboratory experiments were conducted to investigate differential tolerance to root-absorbed [¹⁴C] sulfentrazone by potato, common lambsquarters, and jimsonweed. Common lambsquarters and jimsonweed absorption of [¹⁴C]Sulfentrazone g ^-1 fresh weight was more than twofold that in potato after 24-h exposure. After 48-h exposure, sulfentrazone absorption by common lambsquarters was nearly twofold that in jimsonweed and nearly threefold that in potato. Sulfentrazone movement from roots to shoots was also greater in common lambsquarters than in jimsonweed and potato after 6 h. Both weed species exhibited nearly a twofold increase in sulfentrazone translocation from roots to shoots compared with potato after 12, 24, and 48 h. Minor differences in sulfentrazone metabolism in roots were noted among species after 6 h. Metabolism in roots and shoots was similar in all species after 12, 24, and 48 h. Because the enzyme on which sulfentrazone acts, protoporphyrinogen oxidase, is located in shoot tissue, translocation to shoots is essential for sulfentrazone toxicity. Therefore, differential root absorption and differential translocation of sulfentrazone from roots to shoots are the proposed primary mechanisms of differential sulfentrazone tolerance among potato, common lambsquarters, and jimsonweed.