Figure 4.

Effect of proton gradient modifiers and ABC transporter inhibitors on the transport of ABA-GE into isolated Arabidopsis mesophyll vacuoles. The proton gradient modifiers (dark gray bars) NH₄Cl (5 mm) and bafilomycin A1 (0.5 µm; BafA1) and the ABC transporter inhibitors (medium gray bars) glibenclamide (0.1 mm; Glib) and orthovanadate (1 mm; VO₄³⁻) or their combination (light gray bars) were added in the presence of 4 mm MgATP. NH₄Cl at 5 mm was also tested in the absence of MgATP (white bars). ABA-GE uptake activities were determined at ABA-GE concentrations between 0.8 and 6.2 µm after incubation for 18 min. Values were normalized to the +ATP value and are given as means ± sd from n (in parentheses) independent experiments. Statistical differences versus 100% are indicated (*P ≤ 0.05, **P ≤ 0.01; one-sample Student’s t test).