The efficiency of photosynthesis results from the composition and organization of the plant’s internal structural components as well as the capability of response to environmental fluctuations. This thesis aims at identifying the genetic loci that are regulating the (sub-) processes in photosynthetic acclimation to increased irradiance levels, in order to obtain the genetic information useful to breed for photosynthetic performance. It uses genome wide association studies (GWAS) to reveal which genetic loci are being exploited in nature for keeping good photosynthetic performances in natural conditions. Phenotypic variation among natural accessions in photosynthetic light use efficiency response to increased growth irradiance is related to its variation in genetics in order to identify the associated genetic loci. It is described which light environment reveals most natural variation in photosynthetic performance and for which photosynthetic parameter this is. It shows different Arabidopsis accessions display different photosynthetic responses to various light environments, well relatable to genetic differences. A candidate gene list for the direct response to increased growth irradiance was revealed after performing genome wide association analysis. By identifying and characterizing genes for which different alleles affect photosynthesis responses, some of the regulatory and physiological processes underlying natural variation for photosynthetic acclimation to a step increase in irradiance could be revealed. Next step would now be to screen the germplasm of commercial crops for the presence of beneficial alleles of the genes causal for natural variation in photosynthesis efficiency response to increased growth irradiance identified in this thesis. Subsequent crossing of these beneficial alleles into commercial lines will allow analysis of its effect on photosynthesis in crops, as well as crop yield.