Abstract
The effect of dimepiperate on herbicidal activity of root-applied BSM and also on its absorption, translocation and metabolism were investigated in rice plants. It was observed that dimepiperate significantly reduced the inhibition of root elongation caused by BSM. 14C-BSM was linearly absorbed by rice roots within 24 hours, but addition of dimepiperate caused a decrease of the rate of absorption. There were no differences detected in the rate of translocation of 14C-BSM from roots to shoots between BSM applied alone and in combination with dimepiperate. In shoots, more than 50% of incorporated 14C-radioactivity was found as metabolites, the major one being metabolite A (methyl=α-(4-hydroxy-6-methoxypyrimidin-2-ylcarbamoylsulfamoyl)-o-toluate). In roots, a large part of the 14C-radioactivity was detected in unchanged BSM. Dimepiperate addition increased the rate of matabolism of applied BSM, while metabolite A, B (methyl=α-(aminosulfonyl)-o-toluate), C (1 H-2, 3-benzothiazin-4-(3H)-one 2, 2-dioxide) and other metabolites, including those water soluble were produced in greater quantity. These results sugget that the decrease of absorption rate and the acceleration of metabolism rate by dimepiperate addition is a major factor in the safening action of dimepiperate against the phytotoxic activity of BSM in rice roots.
