Figure 3.

Effect of cadmium and/or AG on the hydrolytic activity of H⁺-ATPase (A) and the ATP-dependent proton transport (B) measured in the plasma membrane vesicles. The plasma membranes (50 μg of protein) were isolated from control roots (control), roots of plants treated for 3 days before harvesting with aminoguanidyne added to control nutrient solution (control/AG), roots of plants, which after 3 days of treatment with 10 µM Cd were transferred to the control conditions for another 3 days (Cd), and the roots of plants, which after 3 days of treatment with 10 µM Cd were transferred to the control nutrient solutions with aminoguanidyne (Cd/AG). Hydrolytic activity of H⁺-ATPase was measured as described in the Materials and Methods. Results are the means ± SD of three independent experiments with each experiment performed in triplicate (A). After equilibration of membranes with the reaction medium (for at least 5 min), vesicle acidification was initiated by the addition of ATP to give a final concentration of 3 mM. The formation of a ΔpH gradient in the vesicles was monitored as the changes in acridine orange absorbance (A₄₉₅). The values presented (B) are representative for the results obtained in three independent experiments with each experiment conducted in triplicate. The results in the inner diagrams (the steady state of H⁺ transport are the means ± SD from those three independent experiments (asterisks indicate the significant differences, where *** p < 0.001).