FIGURE 3.

Vacuolar proton pump activity in Arabidopsis wild-type (Col-0) and ABA mutants (bglu10 and bglu18) root cells under Cd stress. (A) V-ATPase and (B) V-PPase activities in roots of Arabidopsis wild-type measured and ABA mutants under treatment with 20 μmol L^-1 CdCl₂. The proton pumps activity of the wild-type under Cd condition was set to 100%, and the specific activity of the root tonoplast proton pumps were expressed as percentage of that in the wild-type under Cd condition. (C) Cd²⁺ distribution between the vacuole and protoplast in roots; values above the bars represent the percentage of vacuolar Cd²⁺ relative to the total Cd²⁺ in protoplasts; (D) roots total Cd²⁺ accumulated in cytoplasm (P-V) calculated as total Cd²⁺ in protoplast – total Cd²⁺ in vacuole. (E) ${\mathrm{NO}}_3^{-}$ distribution between the vacuole and protoplast in roots; values above the bars represent the percentage of vacuolar ${\mathrm{NO}}_3^{-}$ relative to the total ${\mathrm{NO}}_3^{-}$ in protoplasts; (F) roots total ${\mathrm{NO}}_3^{-}$ accumulated in cytoplasm (P-V) calculated as total ${\mathrm{NO}}_3^{-}$ in protoplast – total ${\mathrm{NO}}_3^{-}$ in vacuole. Data represent means ± SE (n = 4). Bars with the same letter indicate no significant difference at P < 0.05 level by the method of LSD.