Primary photosynthetic processes: from supercomplex to leaf

This thesis describes fluorescence spectroscopy experiments on photosynthetic complexes that cover the primary photosynthetic processes, from the absorption of light by photosynthetic pigments to a charge separation (CS) in the reaction center (RC). Fluorescence spectroscopy is a useful tool in photosynthetic particles, because the latter are densely packed with fluorescence pigments like chlorophylls (Chl). The fluorescence of each pigment is affected by its environment and provide information about structure and dynamics of the photosynthetic complexes. In this thesis time-resolved fluorescence of Chl molecules is used for studying the ultrafast kinetics in membrane particles of photosystem II (PSII) (chapter 2, 3 and 4). In chapter 5 fluorescence lifetime imaging microscopy (FLIM) of is applied to study entire chloroplasts, either in the leaf or in isolated chloroplast form. The advantage of FLIM is that the interactions of the fluorescence pigments in both photosystems can be spatially resolved up to a resolution of 0.5 x 0.5 x 2 µm to indentify and quantify photosynthetic processes in their natural environment. Excitation energy transfer and charge separation in PSII membranes (chapter 2,3 and 4) In this thesis time-resolved fluorescence measurements of PSII containing membranes, the so called BBY particles, are performed in low-light conditions with open reaction centers. The BBY particles do not contain photosystem I (PSI) or stroma lamellae, but do support electron transfer and carry out oxygen evolution with high activity and are comparable with the grana in vivo. The fluorescence decay kinetics of the BBY particles are faster than observed in previous studies and also faster than observed for PSII in chloroplasts and thylakoid preparations. The average lifetime is 150 ps, which, together with previous annihilation experiments on light-harvesting complex II (LHCII) suggests that excitation migration from the antenna complexes contributes significantly to th