AbstractA dynamic model of photosynthesis is developed, accounting for factors such as photoadaptation, photoinhibition, and the “flashing light effect.” The model is shown to explain the reported photosynthesis–irradiance responses observed under various conditions (constant low light, constant intense irradiance, flashing light, diurnal variation in irradiance). As significant distinguishing features, the model assumes: (1) The stored photochemical energy is consumed in an enzyme‐mediated process that obeys Michaelis‐Menten kinetics; and (2) photoinhibition has a square‐root dependence on irradiance. Earlier dynamic models of photosynthesis assumed a first‐order dependence of photoinhibition on irradiance and different kinetics of consumption of the stored energy than used in this work. These earlier models could not explain the photosynthesis—irradiance behavior under the full range of irradiance scenarios—a shortcoming that is overcome in the model developed in this work. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 81: 459–473, 2003.