Effects of Magnesium on Intact Chloroplasts: I. EVIDENCE FOR ACTIVATION OF (SODIUM) POTASSIUM/PROTON EXCHANGE ACROSS THE CHLOROPLAST ENVELOPE 1

AUTOR(ES)

Huber, Steven C.

RESUMO

Exogenous Mg2+ (2 millimolar) altered the stromal pH of intact spinach chloroplasts. Without added KCl in the medium, Mg2+ decreased the stromal pH in the light by approximately 0.3 pH unit. External KCl (25 millimolar) largely prevented the acidification caused by Mg2+. Effects on the stromal pH were not caused by changes in H+ pumping across the thylakoid membrane because Mg2+ had no effect on the light-induced quenching of atebrin fluorescence by intact chloroplasts. However, Mg2+ affected H+ fluxes across the envelope. Addition of Mg2+ to intact chloroplasts in the dark caused a significant acidification of the medium that was dependent on the presence of K+.

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