E. A. Chernyavskaya^* and E. G. Andrizhievskaya

We observed experimentally the nonlinear dependence of fluorescence of photosynthesizing organisms on the density of the flux of photons of exciting stationary radiation from an He—Cd-laser (l = 440 nm). A model of a photosynthetic unit was developed that takes account of the structure of the reacting center (RC) of PS2, the processes of migration of the energy of laser excitation from a light-collection antenna (LCA) to the reaction center with subsequent separation of charges at it, the processes of recombination of charges in the RC, and the reverse migration of energy from the RC to the LCA. Within the framework of this model we explained the experimentally observed nonlinear dependence of fluorescence on the density of the flux of exciting-radiation photons and evaluated the contribution of recombination fluorescence to the overall fluorescence of the LCA.