Author Description

The process of photosynthesis has been studied for centuries, but despite a large amount of progress, there are still many aspects that are not fully understood. An important part of the progress is the fact that many structures of photosynthetic complexes have been resolved 1,2and these complexes have been studied separately in great detail, amongst other with ultrafast spectroscopic techniques. These studies allow to monitor excitation-energy transfer (EET) and charge separation (CS), the first crucial processes after the absorption of a photon. Many picosecond studies have also been performed in vivo in the past before the crystal structures were known, but due to an additional lack of knowledge about the organization and composition of the thylakoid membrane where most of the EET and CS processes take place, the obtained results were difficult to interpret. More recently, new interest has arisen in in vivo studies on photosynthetic organisms because a lot of molecular and organizational information has been obtained but also because the spectroscopic techniques have improved and mutants have become available that allow to study the effect of specific modifications in the organisms. This thesis focuses on the study of the light energy harvesting processes of photosynthetic complexes in cyanobacteria in general by using time-resolved fluorescence techniques, and with particular emphasis on the study of the in vivo protective process of non-photochemical quenching (NPQ) that is induced in the presence of high intensities of blue-green light. .