Figure 3.

Vesicles isolated from sos2 and sos3 plants have reduced plasma membrane Na⁺/H⁺-exchange activity relative to that of vesicles isolated from wild-type (WT) plants. Plasma membrane vesicles were isolated from the leaves of wild-type, sos2, and sos3 plants treated with 250 mM NaCl for 3 days. Transport assays were performed as described in Materials and Methods. When ΔpH reached steady state, NaCl was added over a range of final concentrations (0–100 mM), and the initial rates of dissipation were measured. ●, ■, and ▴, vesicles isolated from wild-type, sos2, and sos3 plants, respectively. The units of Na⁺/H⁺-exchange activity are Δ%F/min per mg of protein.