Photosynthesis models are used extensively to understanding natural cycles, future expectation, necessary precautions etc. Model accuracy, especially the ability to reproduce correctly the temporal variations of the process, is of primary importance. In this study we build and test the performance of a model of photosynthetic activity during the growing season, April to September, using data from NETFLUX measurements for Norunda, Sweden. The site is located in southern border of boreal biome.