Oscillation of delayed luminescence from PS II: recombination of S₂Q⁻B and S₃Q⁻B

Luminescence decaying in the seconds to minutes time scale was studied in spinach chloroplasts and the following results were obtained: (1) After a series of flashes a slow phase which decays in the tens of seconds to minutes time scale was observed to oscillate with a pattern characteristic of S 2 Q − B and S 3 Q − B recombination. This phase was lost upon Tris‐treatment or upon the addition of DCMU. (2) After every flash a small faster phase of luminescence decaying in the seconds time scale was also present. This phase progressively increased with increasing numbers of flashes but when methyl viologen was present no such progressive increase of this phase occurred. In the presence of DCMU this seconds time scale luminescence was greatly increased. This phase of luminescence is attributed to S 2 Q − A recombination. (3) Tris‐treatment resulted in the appearance of an even faster phase of luminescence which may be due to Z + Q − B recombination. These results demonstrate a close correlation of the kinetics of luminescence decay with thermoluminescence emission temperature.