The presented work contributes novel aspects to the understanding of function and co-action of cellular signalling networks in higher plants in the course of acclimation to a changing light environment. The results show that redox signals generated in the photosynthetic electron transport chain have a deeper impact on the cellular signalling network as supposed so far. It was proven that the photosynthetic apparatus acts as an important sensor for changes in the light environment of land plants and that signals originating from the redox state of electron transport components are an own class of plastid signals targeted to the nucleus. From the obtained data, a model is proposed which shows a possible signal transduction derived from the photosynthetic electron transport targeting nuclear gene expression independently of cytosolic photoreceptors. Furthermore a regulatory mechanism for chloroplast gene expression via a phosphorylation cascade starting with the kinase responsible for LHCII phosphorylation is suggested.