Personal recollections of 40 years in photosynthesis research

The major theme of my work in photosynthesis has been electron transport in green plant thylakoids. In particular, we investigated the properties and the role of the NADP-reducing flavoprotein and its possible function in cyc lic electron transport, the regulation by protons of electron transport, an d the redox system of ascorbate and monodehydroascorbate (the ascorbate fre e radical). The function of this system in providing ATP in the stoichiomet ric amount needed for carbon assimilation, and the regulation of the altern ative transfer of electrons to NADP and to the ascorbate free radical were among the achievements of my collaborators and myself. Specifically, the ea rly conviction that cyclic phosphorylation was essential part in photosynth esis was shattered as far as higher plants are concerned, and replaced by a modified Mehler reaction providing additional ATP to run the Calvin cycle. The situation seems to be different in unicellular green algae, where quan titatively much larger changes of the relative size of Photosystem (PS) I a nd PS II antennae during the so-called `state' transitions have been report ed, and these seem to be associated with a high activity of cyclic electron transport in state 2. Beyond the science, the friendly interactions with s o many persons around the world sharing my interest in photosynthesis and i n other aspects of human life have been most rewarding.