Direct demonstration of the involvement of chloroplasts in the rapid light-induced potential change in tonoplast-free cells of Chara australis. Replacement of Chara chloroplasts with spinach chloroplasts.

To directly demonstrate the involvement of chloroplasts in the rapid light-induced potential change we removed chloroplasts by centrifuging tonoplast-free cells of Chara australis. Chloroplast-free cells showed no signs of a potential change on illumination. When a chloroplast-free Chara cell was perfused with a suspension of chloroplasts isolated from other cells of Chara australis, it regained its ability to generate the rapid potential change induced by light. Chloroplasts were isolated from spinach leaves by a method which preserves the chloroplast envelope; thus ensuring the ability to assimilate CO2. When these chloroplasts were introduced into a transparent Chara cell containing no chloroplasts, normal rapid hyperpolarization was induced on illumination. When spinach chloroplasts were treated with a medium of very low osmotic potential, no O2 evolution was detected, but even with these chloroplasts rapid light-induced hyperpolarization was observed. We concluded that chloroplasts are essential for the rapid light-induced potential change and that chloroplasts can be replaced with those of another species, so far as the light-induced potential change is concerned.