Our thanks to Govindjee for providing the following texts: (1) A dedication to him published in 2004; (2) Messages received from Bruno Velthuys, Tinus Pulles and David Knaff; and (3) Some thoughts from the author


2004 Dedication

[Prepared by the late Colin Wraight, Govindjee, and George C. Papageorgiou, with contributions from Hans van Gorkom and Rienk van Grondelle] published in Volume 19 of Advances in Photosynthesis and Respiration, “Chlorophyll a Fluoresence : A Signature of Photosynthesis” , edited by G.C. Papageorgiou and Govindjee]. It reads: 

            During his scientific life, Louis (Lou) Nico Marie Duysens quietly contributed some of the most seminal ideas in photosynthesis, with still central influence over our thinking today. His approach was a perfect blend of deep theoretical understanding and experimental innovation. Typical of Duysens' early work was his insightful application of Förster theory to light harvesting by the accessory pigment beds, which firmly established the physics underlying the function of the photosynthetic unit. Using his own state-of-the-art absorption spectrophotometer, he discovered the spectroscopic signature of oxidation and reduction of the photochemical reaction center in [photosynthetic] bacteria. Later, adapting this technique to plant (algal) systems, he discovered the alternating effects of green and red light on the redox state of cytochrome f in red algae, to firmly establish the now familiar model of Photosystem I and Photosystem II acting in series. These major contributions exemplified Lou Duysens' philosophy towards technical developments. Technology never drove nor limited his research, but was harnessed to address specific scientific questions and hypotheses.

            With his easy understanding of photochemical and photophysical principles, Duysens pioneered the use of Chlorophyll fluorescence as a powerful probe of photosynthetic function, in all classes of photosynthetic organisms, to discover many of the essential events of primary energy conversion in photosynthesis: excitation energy transfer in the light-harvesting antenna and charge separation in the reaction center. Over many years, in his laboratory in Leiden (The Netherlands), a multitude of state-of-the art fluorescence methods was created, driven by the ideas of Lou Duysens. Fundamental concepts that followed from these experiments include the carotenoid to (bacterio-) chlorophyll energy transfer in plant and bacterial light harvesting systems, the efficient energy transfer among a large number of quasi-identical chlorophylls to reach the small population of reaction centers, the ‘Lake model' of photosynthetic unit function, the control of the fluorescence yield of Photosystem II by the redox state of the quencher Q (now known as QA), and chlorophyll excitation quenching by carotenoids. These concepts underlie the veritable industry of fluorescence-based, non-invasive methods now used to study photosynthesis in vivo and to analyze plant productivity, from the lab bench to satellite monitoring.

            Lou's understanding of physical principles is [was] immense and so facile that his colleagues and competitors [always] struggled to keep up with him. His seemingly simple analysis of the thermodynamic limits of photosynthetic energy conversion sparked a literature that lasted several decades, with each incremental advance simply rediscovering what he had said at the outset. Indeed, this is still an area that few fully comprehend.

            Since Lou's retirement, many ultrafast spectroscopic techniques have emerged, revealing intricate details of function in the photosynthetic apparatus, which can be well understood in terms of the fantastic atomic resolution structures of photosynthetic pigment-protein structures that are now available. In this new era of understanding, it is amazing to see how the concepts, developed by Duysens even 50 [60] years ago, have survived as solid foundations of our current models of photosynthetic activity.


Messages from friends of Lou

David B. Knaff: Dear Govindjee :I'm so very sorry to hear this news.  Although Jan Amesz was my day-to-day host during my 1983-1984 sabbatical in Leiden, Lou - in his capacity as head of the [Biophysics] lab - was an incredibly warm and gracious host and, of course, his contributions to our understanding of photosynthesis were enormous.

Tinus Pulles: With the passing away of Lou Duysens, one of the giants of the photosynthesis research community is no longer with us. His legacy, however, is broader than the field of photosynthesis. Although I left photosynthesis research already in 1979, Lou has had an important influence on my scientific development and career. My nine years (1971 --1979) within his Leiden photosynthesis group has taught me that a scientific approach, using the methods and thinking developed and applied within the framework of physics, is instrumental in solving scientific problems in many scientific disciplines, including those of environmental sciences and climate change. He taught me and other PhD students in his group to be stubborn enough to doubt anything as long as it was not clearly proven to be correct and to never accept something only because an "expert" claims it to be true. Together with Jan Amesz, Lou has made me the type of critical scientist I now am. I remember him with great gratitude.

Bruno Velthuys: L.N.M. Duysens has had a great impact on my life. Without his pioneering work in the Netherlands, I surely would never have strayed in the field of Biophysics of Photosynthesis, and as indirect consequence, I would not have worked in Baltimore for eight years, and I would not have raised (up to kindergarten age) a daughter in France. Additionally, I would have missed meeting this uniquely gifted person on a quasi-daily basis for about 4-5 enjoyable years when, adjunct to (and hierarchal above) Jan Amesz, who was my mentor and teacher at the lab in Leiden where I stayed as a PhD-student. Hence, when I read about Lou’s passing away, I was saddened. And I wished to help make sure that the American photosynthesis community also heard without much delay about this occurrence that leads to sorrow and eulogy. I am glad, Govindjee, to see that you in your usual energetic way have picked up on the sad news, and is organizing to publish, in the near future, a Tribute to Lou  in a widely- read journal “Photosynthesis Research”. ------[Please note that I left] Leiden almost 40 years ago; after that I met Lou only a couple of times, but I have fond memories.

Some Thoughts from Govindjee:

            As Wim Vredenberg  (of the Netherlands) wrote to me recently, and I have precisely the same thoughts: Lou Duysens was a brilliant, creative and inspiring scientist (see the personal part of the paper of W. Vredenberg (2015) Photosynth Res 124:87–106), where Wim talks about his work with Lou Duysens).

             Long ago, upon my invitation, Duysens (1989) wrote beautifully about his own work (see L.N. M.Duysens (1989) The discovery of the two photosynthetic systems: a personal account. Photosynth Res 21: 61-79). It is indeed brilliant, but most importantly a real historical account of the two light reaction and two photosystem in photosynthesis. What impressed me most is that he recognized contributions of others, including myself, in the most authentic manner.  

               Lou was my hero since I began my PhD, in September of 1956, in Biophysics (then Physico-Chemical Biology) under Robert Emerson & Eugene Rabinowitch. Duysens's 1952 PhD thesis, and Rabinowitch’s 3 volumes, had served as my “Bible of Photosynthesis”; Duysens’s thesis was read by me word by word; and I used this knowledge in my own research, and that of my PhD students, for years together: most of the early discoveries in my lab were indeed influenced by what Lou had to say. In passing, Lou was the one who had built the difference absorption spectrophotometer in Rabinowitch's Lab when he was a post-doc before I came here. Lou had much praise for Rabinowitch's ideas, and he read very diligently all what Eugene had written.  I went to Lou's Lab in 1976, for my 2nd sabbatical, and it was there that we were able to pinpoint that bicarbonate ion functions at the two-electron gate of Photosystem II (see Govindjee, M.P.J. (Tinus) Pulles, Rajni Govindjee, Hans van Gorkom and L.N. M. (Lou) Duysens (1976) Inhibition of the reoxidation of the secondary electron acceptor of Photosystem II by bicarbonate depletion.  Biochim Biophys Acta  449: 602—605).

Note from Govindjee: Anyone who would like to participate in writing or contributing to a Tribute to Lou Duysens, to be published later in “Photosynthesis Research” is requested to send an e-mail to gov@illinois.edu. Photographs of Duysens alone or with others are also welcome.

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