FAR‐RED INDUCED, LONG‐LIVED AFTERGLOW FROM PHOTOSYNTHETIC CELLS. SIZE OF AFTERGLOW UNIT AND PATHS OF ENERGY ACCUMULATION AND DISSIPATION

Abstract

Abstract— –Small amounts of N ‐methyl phenazonium methosulphate (PMS) added to a suspension of Chlorella pyrenoidosa accelerate the emission of the long‐lived far‐red induced afterglow without greatly changing the amount of light emitted. The effect is noticeable in dilute suspensions at a PMS concentration of 10 ‐9 M. The concept of afterglow unit is introduced and defined as that part of the sample in which the rate of energy reemission can be controlled by a single molecule of PMS. The number of chlorophyll molecules per afterglow unit is about 10 5 . It is possible that the afterglow unit is identical to the thylakoid. The rate constant for the final first order decay phase of afterglow at room temperature is about 0.7 min ‐1 without PMS and about 3 times larger for a unit with one PMS molecule. Diuron (DCMU) lowers the rate of afterglow decay. Desaspidin on the other hand decreases the amount of light emitted without affecting the decay rate. Carbonylcyanide‐ m ‐chlorophenyl hydrazone (CCCP) decreases the afterglow over the whole time‐range and increases the decay rate. A kinetic model is developed to account for the results.