| Popis: |
The absorption, translocation, and metabolism of 14C-labelled mecoprop in a susceptible and a resistant biotype of Stellaria media (L.) were studied under controlled environmental conditions. The difference in susceptibility between the two biotypes could not be ascribed to quantitative differences in absorption or translocation of radiolabel. In fact, more 14C was absorbed into and translocated from leaves of the resistant biotype. Patterns of 14C translocation in the two biotypes were similar and, therefore, could not explain herbicide susceptibilty either. Spraying both biotypes with unlabelled mecoprop prior to [14C]mecoprop application had no significant effect on absorption, but tended to decrease the amount of radiolabel translocated out of the treated leaves of both biotypes, particularly to the roots. Herbicide metabolism was studied in the 14C-treated leaf tissues, where most of the radioactivity remained over the 72-hr experimental period. Both biotypes converted substantial amounts of [14C]mecoprop to more polar constituents, presumed to be conjugated metabolites. However, there was significantly less conjugation in the susceptible compared with the resistant biotype, resulting in more parent herbicide being available in the susceptible plants. Differential metabolism, forming nonherbicidal conjugates, is proposed as a possible mechanism of resistance to mecoprop in S. media. |
