A mathematical representation of the growth of a photosynthetic system in an alternating light/dark regime is proposed, integrating fluid dynamics and maintenance in the three-state model developed earlier by filers and Peeters (1998. Ecological Modeling, 42, 199-215). The model was solved analytically and the constants were fitted to experimental data obtained in a thin film tubular reactor. The theoretical prediction that the introduction of light/dark cycle may enhance the growth, was confirmed by the experimental results, supporting the idea of utilizing ordered mixing to obtain more efficient growth. The model allows to predict collapse of cultures in photobioreactors either under light-deficit or light-excess conditions, as well as the influence of mixing on these critical phenomena. It has also been shown that chlorophyll fluorescence measurements can be used to estimate the growth at steady state. This paper presents an approach to model the kinetics of photosynthetic systems for photobioreactor design under conditions of simultaneous occurrence of photoinhibition in one region of the reactor, and photolimitation in another. The model takes into account the movement of the cells from one region to the other.