1995 Volume 39 Issue 4 Pages 229-236
The safening effect and action mechanism of dimepiperate (S-(α, α-dimethylbenzyl) piperidine-1-carbothioate) on bensulfuron methyl (methyl-2-[[(4, 6-dimethoxypyrimidine-2-yl) ureido] sulfony1]-o-toluate, BSM) were studied using 7-d-old rice seedlings (Oryza sativa L., cv Nipponbare) subjected to water culture. Significant growth inhibition which was observed in the 6×10-8M BSM treatments was alleviated by mixing BSM with 8×10-6M dimepiperate (Fig. 1). A significantly smaller amount of 14C-BSM was detected in the rice roots when BSM was applied with dimepiperate, indicating that dimepiperate inhibited BSM absorption. On the other hand, the translocation of 14C-BSM was not affected by the dimepiperate treatment. When the BSM metabolites were analyzed at 24 and 48hr after the treatments, the content of O-demethyl, BSM significantly increased by the use of dimepiperate, suggesting that dimepiperate affected the detoxification of BSM in rice roots and excised shoots (Fig. 2).
The above mentioned results indicate that the safening effect of dimepiperate on BSM phytotoxicity could be due to a reduced absorption through roots and rapid detoxification of BSM in the seedlings. There was a resumption of the acetolactate synthase (ALS) activity in vivo (Fig. 3), synthesis of branched-chain amino acids (Fig. 4 and Table 1), and 3H-thymidine incorporation into the DNA fraction of the root tips which display a high cell division activity (Fig. 5). The effects are considered to be indirect, and due to the reduced absorption and rapid detoxification of BSM caused by dimepiperate.
