Chlorflurenol effects on absorption and translocation of dicamba in Canada thistle (Cirsium arvense).

Absorption and translocation of the growth regulator '4Cchlorflurenol (methyl -2 -chloro -9 -hydroxyfluorene 9 -carboxylate) and of the herbicide 1 4C-dicamba (3,6-dichloro-o-anisic acid) were studied in Canada thistle [Cirsium arvense (L.) Scop.]. Also investigated was how foliar treatments with chlorflurenol affected leaf uptake and distribution of dicamba by Canada thistle. Plants were grown in aerated nutrient solution. 1 4C-chlorflurenol showed strong acropetal and weak basipetal movement. Thirty-two percent of the foliar applied 14C-dicamba was absorbed and most of the radioactivity tended to accumulate in the young growing leaves. Only 0.6% of the applied radioactivity moved to the roots. Leaf absorption and basipetal translocation of 1 4C-dicamba were increased twoand ten-fold, respectively, by the simultaneous addition of chlorflurenol at 0.6 kg/ha. Root bud activity was increased when 4-week-old Canada thistle plants were foliarly treated with chlorflurenol at 0.6 kg/ha. Field work demon strated that Canada thistle control could be enhanced by chlorflurenol addition to dicamba. Additional index words. Herbicide, growth regulator, bud dormancy.