Chlorsulfuron {2-chloro-N-[[(4-methoxy–6-methyl-1,3,5-triazin-2-yl)amino] carbonyl] benzenesulfonamide} uptake from different pH solutions by leaves and excised root segments of velvetleaf (Abutilon theophrasti Medik. # ABUTH) was examined. In buffer solutions more 14C-chlorsulfuron penetrated intact leaves at lower pH levels (2.4, 3.4, and 4.4) than at pH 5.6. Initial chlorsulfuron absorption by 1-cm segments cut from the apical 5 cm of roots was rapid in the first 10 min for all pH levels. During the first 10 min, roots absorbed more chlorsulfuron from acidic (pH 2.4 and 3.4) than from higher pH solutions (pH 4.4 and 5.6). Chlorsulfuron efflux occurred in two phases for all pH levels. The first phase was a rapid loss through approximately 10 min, and the second a slow loss through 240 min. In the first 10 min, the efflux of chlorsulfuron was faster from roots incubated in pH 2.4 than in higher pH solutions. Efflux from the other pH levels was similar.
