COMPARAISON ENTRE L''EMISSION D''OXYGENE ET L''EMISSION DE LUMINESCENCE A LA SUITE D''UNE SERIE D''ECLAIRS SATURANTS

Abstract— Luminescence of Chlorella cells has been measured after illumination by a series of short saturating flashes.
The intensity of luminescence is strongly dependent upon the number of flashes; luminescence is minimum after a single flash and maximum after a double flash illumination.
If l /_n is the intensity of luminescence measured 0.24 sec after the nth flash, the series l _n shows oscillations as a function of n. The series l _n is very similar to the series y _n, in which y is the amount of oxygen evolved by the nth flash, the term l _n corresponding to the term y _n+1. To interpret the oscillations of the series y _n, different models of system II photochemical centers have been proposed, one by ourselves and the other one by KOK et al. In these models the electron donor Z of photosystem 11 is supposed to have 2 or 4 levels of oxidation, the more oxidized state being the precursor of oxygen. These different oxidation states of the donor Z allow storage of the photic energy in the system. The correlation between the series y _n and l _n shows that at least one of the oxidized forms of the donor Z is a substrate for the luminescence reaction.