An analysis of the consequences arising from the non- linearity of the photosynthetic light curves on the values of quantum requirement, as well as on the action spectra and quantum efficiency spectra in dependence of the suspension optical densities is presented. A kinetic model of the oxygen production reaction is elaborated in which in addition to the non-cooperative (Kok''s)mechanisms a cooperative one is also included. According to this model the oxygen precursors obtained in different oxygen evolving reaction centres could migrate in the surrounding media and recombine. The two widely accepted fundamental concepts, i.e. the concept of the photosynthetic units and the concept of the two photosystems - the Z-scheme, are reconsidered, and completely new ideas are presented. A logical explanation of almost all unexplained up to now important observations – Emerson''s first effect, the red drop effect and Emerson''s enhancement effect, the effect of Blinks'', the inhibitory action of oxygen on photosynthesis - Warburg''s first effect and the effect of CO2 on the photochemical(Hill reaction)activity of isolated chloroplasts is presented.