Selectivity Mechanisms of Sethoxydim Absorption into Tissues of Corn (Zea mays) and Pea (Pisum sativum)

The selectivity mechanisms of sethoxydim {2-[1-(ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one} were investigated by examining absorption of14C-sethoxydim into tissues of corn (Zea maysL. ‘Goldencrossbantam′) and pea (Pisum sativumL. ‘Alaska′). Greater absorption of14C-sethoxydim was observed only into the proliferative 2-mm terminals of the excised roots of susceptible corn, and the same result was obtained with corn seedlings in hydroponic culture. Absorption was not affected by 1 × 10−4M 2,4-dinitrophenol (DNP), which indicated that the absorption of14C-sethoxydim is probably mediated by a passive transport system rather than an active transport system. The selective herbicidal action of sethoxydim appeared to depend largely on the differential rates of absorption into meristematic regions by the susceptible and tolerant plants.