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

Abstract

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.