Absorption, Translocation and Metabolism of Butachlor by Rice Seedlings

Butachlor [2-chloro-N-(2,6-diethylphenyl)-N-(butoxymethyl) acetamide)is one of the most important herbicides for transplante rice (Oryaz sativa L.) weed control in Taiwan. The herbicide was readily absorbed by rice roots. During 24 hours of uptake experiment, 32% of the applied herbicid was absorbed. The pretreatment of the herbbicide for 2 days did not affect the absorption.Of the absorbed herbicide,80% remained in roots, only 20% translocated into shoots, and more than 50% was metabolized to water soluble substances. Thin layer chromatographic (TLC) analysis showed that the Rf value of the most abundam metabolite was the same as butachlor-glutathione conjugate. Rice, barnyard-grass(Echinochloa crusgalli(L.) Beauv) and monochoria(Monochoria vaginalis Presl) seedlings contained rclatively high level of non-protein thiols, whilc the glutathione S-transferase (GST) activity was highest in ric, barnyardgrass the next, monochlorla the lowest. The difference in GST activity among these species might be related to their sensitivity to butachlor.