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 Mg(2+) concentration ([Mg(2+)]) in chloroplast. Stromal [Mg(2+)] was increased by dark incubation of chloroplasts in the K(+)-gluconate medium (pH 8.0), or by NH(4)Cl. These results indicate that stromal alkalinization can induce an increase in stromal [Mg(2+)] without illumination. Some inhibitors of envelope proton-translocating ATPase activity involved in H(+) efflux inhibited the alkalinization-induced increase in [Mg(2+)].