Slow release of chloride from ³⁶Cl‐labeled photosystem II membranes

Photosystem II (PS II) membrane fragments isolated from spinach cultured on a medium containing 36 Cl − retain a significant amount of radioactive chloride corresponding to at least one Cl − per PS II unit. The release of chloride from these sites occurs with halftimes of several hours. Treatments which cause the release of the manganese and/or the extrinsic proteins also result in the loss of chloride from these sites, indicating a possible role for this chloride in photosynthetic oxygen evolution.