During his post-doctoral fellowship at the University of Cambridge, he was in the laboratory of Enid MacRobbie and studied the ionic status of chloroplasts. He investigated the role of compatible solutes in energy transduction in chloroplasts and wrote the paper Ionic Relations of Chloroplasts in Vivo published in Nature, showing that chloroplasts have much higher salt concentrations than the surrounding cytoplasm and that this difference is involved in energy transduction. At this time, he was also involved in developing early applications of underwater (SCUBA) techniques to plant physiology, particularly the ways in which algae harvest energy in situ. In 1968, he joined the University of Pennsylvania for a postdoctoral fellowship on energy transduction in chloroplasts.
