A Dynamical Model to study the Response of Microalgae to Pulse Amplitude Modulated Fluorometry

International audienceOn-line monitoring growth of microalgal based processes is a challenging issue. Pulse Amplitude Modulated (PAM) fluorometers, used to closely monitor the physiological state of photosystems, do not provide an estimation of the growth rate, a critical information for culture management. We designed a model to represent the relation between the fast dynamics of photosynthesis and the slower process of cell growth in microalgae as a function of light. This model provides a synthetic view of photosystem II photochemistry and accounts for the main two states (open and closed) of photosystem II reaction centres as well as the following electron transport chain. The model is used to analyse the link between a very fast process (the transition between closed and open states), an intermediate one (the filling of the quinone-plastoquinone pool) and a slow process (growth rate fluctuations). Experiments were conducted on the Haptophyceae Tisochrysis lutea. Model parameters were calibrated on the measured fluorescence data. A slow-fast analysis is presented to describe the system dynamics. Results provide new insights for understanding and interpreting PAM measurements