In honor of Reto Jörg Strasser: A pioneer of chlorophyll a fluorescence research.

Chlorophyll (Chl) a fluorescence measurements are widely used in the study of photosynthesis, and Reto Strasser is a well-known pioneer in this domain. In 2019, the current authors, together with Vineet Soni, and Neera Bhalla Sarin, celebrated his 75th birthday. Here, we pay tribute to him on his 82nd birthday through a brief description of the key results we had obtained with him, over the years, on the understanding and exploitation of the OJIP Chl a fluorescence transient. The topics of these studies have been quite diverse, from the oxygen clock, the bicarbonate effect in Photosystem II, the adaptability of plants to various stress factors, to mathematical modeling of the OJIP phase, but all based on the application of Chl a fluorescence for the understanding of oxygenic photosynthesis. Additionally, we have included here a list of the authors who have honored Reto Strasser in Photosynthetica in 2020, along with references of their papers.