Table I.

Influence of BFA on the accumulation of [14C]2,4-D and [3H]NAA

ComponentAccumulation Ratio after 30 s
Control cellsBFA-treated cells
 Total accumulation0.60  ± 0.010.60  ± 0.01
 Nonsaturable component0.32  ± 0.010.35  ± 0.01
 Saturable component0.28  ± 0.010.26  ± 0.03
 Total accumulation0.67  ± 0.020.81  ± 0.02
 Nonsaturable component0.96  ± 0.040.82  ± 0.01
 Saturable component−0.28  ± 0.04-a −0.01  ± 0.02-a

Accumulation of [14C]2,4-D (96–104 nm external concentration) and [3H]NAA (17–27 nm external concentration) was monitored over 30 s in suspension-cultured tobacco cells that had been exposed to 25 μm BFA or ethanol (control cells) for 60 min. Accumulation values were derived from the radioactivity accumulated in cells as described inMethods. Nonsaturable uptake components, corresponding to diffusion, were measured in the presence of 50 μm unlabeled auxin and are uncorrected for contamination by the incubation medium. Saturable components, representing the activity of the influx carrier ([14C]2,4-D accumulation) and that of the efflux carrier ([3H]NAA accumulation), were calculated by subtracting the radioactivity measured in the presence of unlabeled auxin from that measured in its absence (total accumulation). Data, expressed as accumulation ratios, are means ± se of values obtained in two independent experiments, each with three replicates.

    • F0-a Negative values correspond to auxin efflux.