Effects of Alkalinization and ATPase Inhibition on Stromal Free Mg2+ Concentration in Spinach Chloroplasts

Our earlier studies indicate that stromal alkalinization is essential for light-induced increase in free Mg2+ concentration ([Mg2+]) in chloroplast. Stromal [Mg2+] was increased by dark incubation of chloroplasts in the K+-gluconate medium (pH 8.0), or by NH4Cl. These results indicate that stromal alkalinization can induce an increase in stromal [Mg2+] without illumination. Some inhibitors of envelope proton-translocating ATPase activity involved in H+ efflux inhibited the alkalinization-induced increase in [Mg2+].