AN ASSESSMENT OF THE POSSIBLE REASONS FOR DIFFERENTIAL TOLERANCE TO FLUROXYPYR IN SELECTED POPULATIONS OF GALIUM-APARINE

In an investigation of the possible reasons for tolerance to fluroxypy r by Galium aparine L. (cleavers), a wide range of variation in total herbicide retention was exhibited by nine diverse populations from thr oughout Europe. Although these differences in fluroxypyr retention bec ame negligible when considered on a unit area basis, a two-fold differ ence was maintained per unit dry matter. There was no difference in fl uroxypyr uptake between a fluroxypyr-tolerant and a fluroxypyr-suscept ible population, and differences in translocation between the two popu lations did not seem to explain the differential tolerance. It is sugg ested that differential metabolic detoxification may be the main reaso n for the variation in response to fluroxypyr by populations of G. apa rine.