Studies were initiated to evaluate absorption, translocation, and distribution of ¹⁴C-quinclorac in propanil- and quinclorac-resistant (R-BYG) and -susceptible (S-BYG) barnyardgrass. No differential absorption of ¹⁴C-quinclorac was observed between R-BYG and S-BYG, but more ¹⁴C remained in the treated leaf of S-BYG (57% of total absorbed) compared with the R-BYG leaf (34% of total absorbed) at 72 h after treatment (HAT). After 12 HAT, 20 and 15% of the amount absorbed had been translocated basipetally by R-BYG and S-BYG, respectively. At 72 HAT, 27 and 17% of the total absorbed ¹⁴C had been translocated acropetally by R-BYG and S-BYG, respectively. The levels of ¹⁴C above the treated leaf continued to increase throughout the duration of the experiment in R-BYG while levels of ¹⁴C above the treated leaf in S-BYG remained relatively constant. Seven percent more of the total absorbed ¹⁴C was exuded from roots of R-BYG than S-BYG at 72 HAT. Although differential translocation was observed between R-BYG and S-BYG, it is unclear whether this difference is a cause of quinclorac resistance or an effect of some other physiological process. Further research is needed to determine if differential translocation is due to metabolism or other physiological factors.

Nomenclature: Quinclorac, barnyardgrass, Echinochloa crus-galli (L.) Beauv. ECHCG