The involvement of Ca(2+) in the Ca (2+)-effect on Photosystem-II oxygen evolution.

A number of recent reports have concluded that Ca(2+) is not released by treatments which are usually thought to induce the depletion of Ca(2+). Consequently, it was proposed that the Ca(2+) demand was not related to a specific rôle for Ca(2+) in Photosystem-II oxygen evolution. In this letter, we scrutinize the data behind these conclusions and argue that, based on these data, it is premature to question the view that intrinsic Ca(2+) is actually being released.