Salts and chloroplast fluorescence.

Chlrorplast fluorescence was exicted by a weak measuring beam. A time-separated actinic light was used to modify the redox states of Q which in turn induced a change in the fluorescence yield. In salt-depleted chloroplasts, fluorescence saturated at a low actinic light intensity. CaCl2 increased the "variable" fluorescence as well as the rate of ferricyanide-Hill reaction. With Tris-washed chloroplasts, Photosystem II donor couple, phenylenediamine and ascorbate, did not increase the fluorescnece to a large extent without the presence of CaCl2. It is suggested that salt-depletion inactivates the Photosystem II reaction center of chloroplasts.