Abstract
In 2017, when 3 Nobel Prizes were awarded for unraveling the molecular basis of circadian rhythms, 4 of us, former PhD students of Erwin Bünning, met inadvertently in Tübingen, Germany, and gathered in a Weinstube until late into the night to exchange memories about our revered “Doktorvater.” Bünning was 1 of the 3 founders of the field of circadian rhythms, also called chronobiology, along with Colin S. Pittendrigh and Jürgen Aschoff. However, we reminded each other that Bünning had already published in 1931 experimental evidence that the leaf movements of the bean plant, Phaseolus multiflorus, are independent of 24-h changes of light and dark (i.e., they display an endogenous periodicity, later called circadian; Bünning, 1931) and in 1932 that they are inherited (Bünning, 1932). In 1935, he published his observation that the eclosion rhythms of Drosophila continue under constant conditions (Bünning, 1935). In 1936, he proposed that endogenous rhythms (the circadian clock) have adaptive values, for example, for measuring the length of days (photoperiodism) and for controlling diverse physiological processes or behavior (Bünning, 1936). He detailed this model in 1960 at the Cold Spring Harbor Symposium, and Pittendrigh coined it there as the “Bünning hypothesis” (Bünning, 1960; Ward, 1971).
Pittendrigh and Aschoff contributed later to the field of chronobiology with their own rigorous research. The combined research of the 3 scientists led to a paradigm change from the assumption that external cues drive the daily rhythm in organisms to the empirical evidence that circadian rhythmicity in organisms, from fungi, plants, animals, and humans, is intrinsic, independent of environmental cues, and entrained by environmental cycles such as day and night. From there on, chronobiological research increased explosively.
The first edition of his book Die physiologische Uhr, published in 1958, and the second edition translated into English in 1964 were the first textbooks on chronobiology. Bünning summed up the data known up to then, supporting the fact that all organisms, down to single cells, display circadian rhythms and more that the circadian clock belongs to the fundamental features of all living cells. Several hypotheses were proven later, among them that multicellular organisms must be seen as multioscillator systems. Importantly, he also predicted that in animals, control centers regulate and coordinate downstream circadian clocks and synchronize them with external rhythms, while plants lack such control centers and external signals synchronize the independent oscillators.
Bünning was not only an eminent, internationally known, and much honored scientist. As head of the Physiology Department of the Botanical Institute in Tübingen, Germany, his fame, liberal attitude, distance from an authoritarian university system, absolute demand for excellence, and teaching skills made him a magnet for students eager to do their PhD work under his guidance. His broad research interests provided ample topics and included a vast number of organisms from cyanobacteria, fungi, algae, higher plants, insects, and guinea pigs. The breadth of the publications is outlined in Engelmann (2019).
Typical for his generation, Bünning seldom spoke about his life during the Third Reich. Nevertheless, we learned some details later and also found some in documents. For example, we learned from his daughter that both Bünning and his wife, Eleonore, were active members of the Internationale Sozialistische Kampfbund before the war. Although many members of the organization were incarcerated, the Bünnings were spared. However, in a document of the Staatskommissariat of the Denazification (Landesarchiv Baden-Württemberg), which he had to fill out in July 1945 to be allowed for any official position, he stated that in 1933 their house was searched several times, he was interrogated, and Eleonore was fired from her job.
In 1935, while Bünning was assistant professor at the Botanical Institute in Jena, he describes being harassed by Nazi students who accused him of being a Communist, which compelled him to leave Jena for a lectureship position at the University of Königsberg. In 1939, he was drafted and served in Norway until July 1944, when he apparently achieved his own dismissal using a faked stamp made from a raw potato. Since he was proven never to have been a Nazi party member or sympathizer, he received a full professorship in botany at the University of Cologne in 1945. One year later, he was appointed professor of botany and director of the botanical garden at the University of Tübingen, where he stayed until his retirement, even though he received 2 attractive offers for the chair of the Botany Department in Munich in 1953 and in Göttingen in 1957.
Clockwise from upper left: portrait of Bünning in the mid-1960s, photo by M. Grohe; in greenhouse checking orchids, 1966; lecturing at Kyoto University, September 1978, photo by Professor Masashi Tazawa.
Bünning in Lapland. Upper and lower left, September 1972; upper and lower right, March 1962.
Our discussion that evening in the Weinstube covered some of the many facets of Bünning’s rich life and his accomplishments, impact on scientific politics in Germany, and many honors. More details about these facts can be found on the Internet and in Plessse (1996), Chandrashekaran (2006), and Engelmann (2019). Our fondest memories of this evening, however, focused on our personal interactions with Bünning from the late 1950s into the late 1960s, as outlined in the following.
How We Met BüNning
Studying biology and biochemistry in Hamburg and Munich, I heard of Professor Erwin Bünning and his research on the “biological clock” in Tübingen. Therefore, I decided to enroll at the University of Tübingen and to ask Bünning for PhD work. I got an appointment at the Botanical Institute on February 7, 1961. Bünning had prepared for this meeting: he had papers on lunar periodism on his desk, and after a 30-min introduction to the field, he asked me for my place of birth, because I did not speak “Schwäbisch” (the dialect of the region), and my birthday, and he was quite happy that I was also born in Hamburg (as he was) and had my birthday together with his youngest daughter (as I found out later). He then asked me whether I could start the next day. I responded that I could come to Tübingen only at the beginning of May, and he then replied that he would send me literature to prepare myself. In March I received a number of papers by mail, and in May I started my PhD work. I “inherited” the algae, Dictyota dichotoma, from Dieter Müller (later professor in Konstanz), and from that time onwards, I was engaged in the effect of moonlight on the reproduction of D. dichotoma.
This was an extremely interesting period in Tübingen. Bünning passed by nearly every morning, and we had a shorter or longer discussion on biology and philosophy and life in general. At Christmas time 1961, I had to stay in Tübingen for my algal experiments, and everybody in the Bünning lab asked me to take care of their research organisms. I thus watered beans and Kalanchoe, tended algae, counted eggs of Dictyota, fed cockroaches, caterpillars, guinea pigs, and mice. Bünning and his wife invited me to their house for Christmas so that I did not have to be alone in the Institute. I felt very much at home with his family.
To see how the lunar period was influenced by the circadian rhythm, I had to prolong or shorten the day length manually to either 25 or 23 h, respectively. That meant getting up often nearly every hour during the night, similar as you, Willi, did. For continuing my PhD work, it was necessary to incorporate new methods to follow the lunar periodism of the algal reproduction by measuring the CO2 incorporation over time in Dictyota. The results brought us to a model of how circadian and lunar rhythms interacted to regulate reproduction, which happened every fortnight for 3 days early in the morning and was induced by moonlight.
Vera, I also met Bünning coming from a different university, the University of Hamburg. I fled in 1950 from East Germany to Hamburg in West Germany and started studying physics, chemistry, and biology there in 1953. I got to know 2 biology students from Tübingen, and I was so impressed by their knowledge that in 1955 I decided to continue my studies there. In a lab course in botany, Bünning somehow learned that I was short of money since I had to earn my living and the tuition fees. I was therefore extremely thankful to him when he offered me a job as an assistant. I had to prepare the demonstrations for his plant physiology lecture. He also told me that Professor Walter at the University in Stuttgart–Hohenheim was looking for a PhD student for mapping the flora of a valley that was going to be flooded to produce electricity. I was, however, so interested in Bünning’s work on biological clocks that I asked him to accept me as a doctoral candidate. He agreed and proposed that I work on the relationship between the circadian clock and photoperiodism in the Crassulacean plant Kalanchoe blossfeldiana. As in your case, Vera, he gave me a package of publications, specifically those of Harder and his group in Göttingen and Georg Melchers, one of the directors at the Max Planck Institute for Biology in Tübingen, to become knowledgeable in the topic. I had a hard time reading these papers since I had learned only Russian in school.
At the start of the summer term of 1957, I enrolled in the beginners’ botany lab course. Bünning scheduled the introductory session on the first Saturday, but I had signed up for a weekend retreat of the protestant student organization. Although I had signed up for the course, my name was not on the final participant list. I was surprised and decided to complain to Bünning. In order to see him, I had to request access from his secretary and “gate keeper,” but to my surprise she agreed to ask his permission for a meeting. I had to knock at his office door and wait until he invited me to enter his office. As I entered, his imposing figure sat behind a large desk staring at me sternly through his glasses. I naively asked him why my name was removed from the list of enrollees and tried to explain why I had not attended the introduction. He cut me off abruptly and said, “If your main goal is studying biology, you have to commit 100%. If not, why don’t you forget it and rather study something else like theology.” And that was it. This was one of the best short lectures I ever received in my life. In the end, I managed to take the course. You, Wolfgang, helped me by talking to the assistant who ran the course and by loaning me your microscope since all lab microscopes were being used by the other students who were admitted. At the end of the semester, Bünning signed my course paper personally (there were no exams at that time) without even looking at me. I guess that he acknowledged that I had found a way to take the course successfully. My story of how I became a PhD student of Bünning is different than yours, since I started and pursued my studies in Tübingen. I wanted to become a high school teacher and was required, therefore, to take a teacher’s exam, equivalent to a master’s degree today. This entailed a 1/2-year research project followed by a written and oral exam in 3 different major fields. Bünning’s research and personality had impressed me. I therefore asked him whether I could conduct a small research project under his guidance. He ventured far out from his normal research interest and sent me to the Biological Station on the island of Helgoland (off Hamburg in the North Sea) to investigate whether the mussel Mytilus edulis could be a feasible object to study endogenous tidal rhythms by measuring their filter activity. However, this method did not render reproducible results, nor did the attempt to measure opening and closing movements of their shells. We both decided not to continue this study, but my efforts earned an “A” from him. After I passed the written and oral teacher’s exam in the spring of 1965, I approached Bünning again asking him to accept me as a PhD student under the condition that I could work with an animal (other than Mytilus), not with plants. When I voiced my request, he looked at me, smiled, thought briefly, and said, “Why don’t you go to Engelmann and talk about a topic with him working with Drosophila.” He did not ask me to read any papers. Thus, you, Wolfgang, became my primary mentor. Together with Bünning, we settled on the topic to investigate whether the interaction of 2 rhythms, one induced by the transition from light to darkness and the other one by the transition from darkness to light, would determine the timing of the eclosion rhythm of Drosophila. You, Wolfgang, had already investigated a similar hypothesis for the photoperiodic reactions of Kalanchoe.
As a biology major at the University of Tübingen, I knew Bünning from several lectures, seminars, and courses. Attracted by his personal charisma and his research on endogenous rhythms in plants and animals, I decided in 1963 to ask Bünning for a subject for my PhD. Before I went to him, I discussed with friends and several of his PhD students their work and possible interesting topics for my future work. As a result, I decided to approach Bünning and suggested to investigate whether the circadian clock is still maintained in plants living under constant light conditions in the Arctic midsummer. Bünning first listened very passively as I explained my plan but suddenly became interested and spoke quickly. He elaborated on my ideas and proposed that Svalbard, one of the most northern-located islands (i.e., north of Norway and only 1200 km from the North Pole) seemed suitable for the project, as a number of alpine circum-polar plants grow there during midsummer. He pointed out that the periodic leaf and petal movements of the plants needed to be monitored in their natural environment. Furthermore, he found it important to gather seeds and transport plants from Svalbard to Tübingen. He also thought immediately of the possibilities for financial support, which he received from the German Research Foundation, and suggested that a second person should accompany me. He had laid down the baseline for my PhD project within half an hour. As I learned later, this quick-thinking style was characteristic of Bünning. The subject of my PhD work made it possible to combine adventurous travel with field research and lab work in Tübingen. This corresponded to my interest.
When Bünning offered that I accompany you to Svalbard, all expenses paid, I agreed immediately, exhilarated about the adventure ahead.
Bünning as PhD Advisor
To investigate the lunar periodism of the reproductive cycle of Dictyota precisely, Bünning allowed for a modern radioactive laboratory to replace the former living rooms for the gardeners on the first floor of the small brick building abutting the tropical greenhouse (known as Palm House) in the botanical garden where you, Willi, had your office on the second floor. This modern method of measuring photosynthetic activity was initiated by a new coworker of Bünning, Gerhard Richter, who just came back from Pasadena, California, where he had worked on photosynthesis of the blue green algae, Anacystis nidulans. Now I was able to measure the CO2 incorporation over time. The results brought us to a model of how circadian and lunar rhythms interacted to trigger the reproduction induced by moonlight, which happened every fortnight early in the morning. It is noteworthy to emphasize how Bünning was always interested in the newest modern techniques. At the time of my PhD work, molecular biology of the cell became a hot topic. The Max Planck Institutes of Virology and Biology in Tübingen had been founded to pursue cutting-edge research in these fields in Germany. Bünning picked up on this trend. He was the main motor for the establishment of the chairs of Microbiology and General Genetics at the University of Tübingen during the early 1960s. Also, the foundation of the brand new Universities of Bremen and Konstanz with an emphasis on the sciences were possible only with his active support.
I passed a first version of my dissertation shortly before Bünning left for one of his many Lapland field trips. He returned it the next day with a few corrections and said, “Please, finish it up, and when I am back after 14 days it should be done.” So, that was Bünning, always straight-forward, correct, and consistent.
This reminds me that he also read the first draft of my thesis overnight and gave it back to me saying, “I don’t understand one word, rewrite it.” He also advised me to write in the Discussion section only what I would be sure to repeat again after 20 years, advice that I always remembered when I wrote my future papers. The second draft I delivered and he accepted was thus very short, not even 50 pages long.
On July 4, 1963, Rotraut Ammermann and I had our oral PhD exam in biochemistry, zoology, and botany. Afterwards, a great procession with myself in the middle walked around the university and the botanical garden, and in the evening we continued in the famous Palm House, where our colleagues—especially Claus Schilde and our Lapland buddies—had prepared a huge party among the cacti and palm trees. Certainly Bünning celebrated with us.
In 1961, we started the tradition in the Biology Department that all grad students who passed their final exam were dressed with funny hats and other adornments and hauled around in the streets in a primitive wagon to the amusement of the people on the streets. Dietmar Todt (later professor of animal behavior in Berlin) was the first PhD student who was decorated with a cloak showing his experimental plant Cichorium intybus. I still have pictures of many of us.
For my PhD work, I was measuring the photoperiodic reaction of the short-day plant Kalanchoe by counting the number of flowers induced. Parallel to it, I also recorded the petal movement. At that time, this was quite cumbersome. However, instead of measuring the distance between the tips of the petals with a ruler, as was done in Göttingen, I took shots with a camera, developed the film, and determined the degree of opening of the flowers under a dissecting microscope. This was quite demanding, since it had to be done every 3 h for several days and nights, so I was relieved when Bünning asked Anand Karve from India to join my research on the flower clock of Kalanchoe and we could share the night work. Bünning used for his experiments usually simple methods. But he saw the advantage, especially after we replaced this method by using a photocell underneath a group of cut flowers mounted in a lucent dish floating on a sugar solution. We measured the voltage of the photocells with a special recorder, which allowed us to record the output of several devices for many days.
To illustrate Bünning’s often simple but up-to-the-point explanations is a letter in response to a manuscript he received from one of his former PhD students. It was about the temperature effect on photoperiodic flower induction, and the author claimed that the critical dark period in this short-day plant was temperature dependent. Bünning pointed out that there is indeed an influence on flower formation, since at lower temperatures such as 18°C there are few and at still lower temperatures such as 15°C no flowers formed. Bünning compared the results to the control of an incandescent bulb in an air-conditioned room by a timer. Twelve hours after onset of the dark period, the bulb is switched on for 12 h. If the voltage is now lowered from 220 to 180 V, the lamp will be on again but shines much dimmer. If the voltage is further reduced and no light can be seen any more, “würden Sie es doch als gewagt betrachten, daraus zu folgern, dass die Uhr nicht mehr läuft”—you wouldn’t conclude, that the timer is not running any more, would you?
Since the main botany building was jammed with faculty, staff, and students, Bünning assigned me and another PhD student, Hans-Günther Rentschler, an office in the small brick building, Vera, as you already talked about.
As far as I remember, Bünning had 75 PhD students in his lab over time and many more students working on a thesis for their teacher’s exam. I am sure that each of them could tell a story similar to ours.
I was usually in the office before 7 a.m. At 8 a.m. sharp, I saw Bünning walking through the botanical garden, hands folded in the back and looking at the abundance of flowers and/or surrounding the beautiful pond where lotus plants and Amazon lilies grew. At the end of his walk, he must have often visited you, Vera, to discuss with you, as you pointed out. One morning when I had camped in the office after a long party and was in the process of shaving, there was a knock on the door, and Bünning entered the room. As he saw me still having a hangover, he excused himself and wanted to turn around, but I invited him for a cup of tea (which he declined), but he sat down to talk about my project for quite a while. These were one of the rare moments when I knew how much he cared about what I was doing, even though his normal response to my reports was the same as you, Wolfgang: “nice, nice, just go ahead.” Working with Drosophila eclosion rhythms was much work at our times—no computers, no machines. To monitor the emergence peaks of flies of a population of mature pupae, we knocked the eclosed adult flies from small milk glasses in which the larvae were reared into glasses filled with detergent water and then counted the flies by hand. This was done every 2 to 3 h over the course of 5 days. Worse, to monitor the rhythm after the transition from light to dark, yielding the emerged flies needed to be done in total darkness. I found then that red light beyond 650 nm did not initiate an eclosion rhythm in Drosophila cultures reared in dark, but all shorter light frequencies did. This was the first proof that red light can be used as a “safe light” for Drosophila. From then on, I did not have to work in total dark anymore. Bünning gave me a pat on the shoulder as I reported about my findings and readily agreed to buy the expensive red light fluorescence bulbs with a cutoff below 650 nm.
All of the experimental rooms for the rhythm research were in the cellar of the so-called Bunker, a separate building where he resided on the second floor. Since I needed to get up at night every 2 h for a sequence of 5 days, I asked him whether I could put an air mattress into the cellar to sleep on it between the counts. Instead, he gave me a key for his holy library on the first floor and told me to sleep on the couch there but to make sure that none of his rare books would disappear.
Although Willi and I examined thoroughly more than 40 plant species for rhythmic phenomena in Svalbard as Bünning had suggested, we found no signs of diurnal leaf or petal movements. However, he also had advised me to find the rare arctic dandelion (Taraxacum arcticum). He had dug out a publication about the flora of Svalbard with a vague description of one location where it had been found. Since the dandelions in middle Europe show diurnal leaf movements, he thought this plant would be a good object to study. We found the plants, brought back seeds, and the plants were raised in the lab under controlled conditions. In these plants and also in Arnica angustifolia, another plant species that we had transported from Svalbard to Tübingen, it was possible to show that they indeed displayed weak leaf movements, indicating that they still possess an (endogenous) circadian clock. For the completion of my PhD work, Bünning suggested that I compare these rhythms with circadian rhythms of plants from different geographical latitudes.
Lapland
Since 1951, Bünning offered a 2-week field trip to Lapland, Sweden, each year. He usually went there in the summer but also in winter. For him, it was a source of escape from his hard work and all his responsibilities, recreation for his mind and soul, a place where he drew new energy, sorted his thoughts, and planned future work. He claimed that Lapland was the only place where he could sleep without problems. These trips were highly sought after by all students who studied with him and were affordable since he claimed that they were subsidized by a rich American sponsor. However, he never disclosed the source to us.
I was one of the lucky ones during the summer of 1953. We started in Abisko, followed the Kungsleden (Kings Way) to the south, and visited Muddus National Park with its old-growth forest and large boggy grounds and many mosquitoes. Bünning was a master at carrying the lightest backpack. He slept with his son Otto in a very light tent. We hiked through the mountains, crossed the Norwegian border, and walked down to a fjord. While waiting for a bus back north to Narvik, Bünning bought each of us a cup of ice cream with the result that most of us got diarrhea. From Narvik we took the “Nordpilen” train back to Stockholm.
We both went on this field trip in the summer of 1961, together with 7 other students, and we took the same route, starting as you did, Wolfgang, from the railway station of Abisko at the enormous Lake Torne Träsk and also ending up in Narvik. For us it was a 13-day hike. We each had to carry our own tent and food. To keep our luggage as light as possible, he taught us to cut our toothbrushes in half. He loved living with only the bare essentials for himself and the students.
I remember especially the 3-day train travel from Tübingen to Abisko, interrupted only by a brief stop in Stockholm. We got to know Bünning as a great master of the German card game “Skat” and as a gifted entertainer who knew all of the “Little Erna jokes,” typical jokes told among the Hamburg folks.
On the hike, we experienced many tough conditions: rain, muddy trails, soaking wet bogs, huge slanted granite slopes, leaky roofs of small cabins, wet tents and clothes, braved river crossings and a lake in a leaky boat, as well as thousands of mosquitoes covering our hands as soon we sat down that, thankfully, were blown away on windy days.
I will never forget the one lake crossing where we were exposed to high wind, lightning, and choppy water. Our small boat held only 4 of us and was leaky. Thus, one of us had to bail out the water with a cooking pot as fast as possible while Bünning plugged the holes between the wooden planks with moss using his hunting knife with the wind blowing into our faces. We were relieved when all of us reached the other side of the lake, wet but without drowning! One had a pipe that was lit and passed around among us, including our professor, to celebrate that we all crossed unharmed.
Such trials were rewarded by magnificent views over an endless open landscape, with high mountains and small glaciers around the Kebnekaise, the highest mountain in Sweden. The descent from the higher Swedish plateau down to Narvik at the Atlantic was impressive. The train ride to Stockholm was, in our case, interrupted in Abisko. In a hotel there we enjoyed our first shower after 13 days; heavenly!
On the train back, we received the shocking news that the East German government had started to erect a wall along the East-West German border.
On our trip, Bünning was always in good spirits, encouraged everybody when we felt miserable because of the rain and wind, distributed his tomato paste from the many tubes he carried, joked, told stories of the other field trips including the one where you, Wolfgang, participated. In short, for us it was an unforgettable experience. More importantly, it provided us with a new perspective of our revered professor and allowed us to develop a personal relationship with him since we had experienced him as being one of us. Equally as important, he set an example for us by displaying absolute leadership qualities, also under the toughest conditions.
I would like to add an account of one of the field trips in March 1962 when it was still winter in Lapland. Bünning led us on a similar route as in summer on our old-fashioned skis up and down the hills using the small primitive cabins as night shelters. The trip was even more spectacular than in summer, and there were no mosquitoes and wet bogs but, instead, frozen rivers, powdery snow, and a majestic white landscape. Only some shrubs or small trees, especially the many white birches, were visible under heavy snow, but we saw tracks of wolverines, polar foxes, snow hares, and snow grouses. The temperatures often fell below −4°F. In the evenings when we arrived nearly frozen, Bünning immediately lit a fire in the primitive stoves, as he did every morning. Rice and tomato sauce and other dried vegetables or fruit were ready to be eaten soon after. We especially appreciated a sip of 80% rum or moonshine after our arrival to help us recover from our day’s trek. In one of the cabins, too small for enough bunk beds, Bünning insisted on sleeping on the floor. Christoph Hemleben (my husband and paleontologist) was so fascinated by my story about this trip that he later went twice with Bünning in winter.
Vera, I was part of Bünning’s winter trip in 1964. My experience was very similar to yours, except that we had really bad weather from the start on to the fourth day, snowstorms that grew worse every day. Despite this, Bünning, our guide, equipped with map, compass, local knowledge, and good instinct for the correct direction, was able to find the way from cabin to cabin through the unchartered winter landscape. What really impressed us most after reaching the cabins was not the speed with which he lit a fire in the stoves but the drying method for his wet socks. He took one, pressed it on the hot stove so that we could hear a hiss and saw steam rising. He then quickly turned the sock and did the same with the other side. He repeated this procedure until the sock was nearly dry. On the last day, as we approached the Kärsavagges hut, we met the first people after 8 days of solitude. They were Swedes from Abisko going ice fishing. They had drilled a round hole into the ice, built a small wall of snow against the wind, and placed a reindeer skin on the ice. Lying on the skins, they looked into the hole and moved the short angel with small movements of the hand and, thus, the lure. Bünning asked whether we could use their equipment. To our delight we caught about a dozen, mostly small, fishes. Even though small, the fried fishes provided the first meat after 8 days of spaghetti and tomato paste.
Many of us who were there for the first time with Bünning got hooked on this fascinating place and revisited this area again, but nobody could trump Arnulf Haury, one of his students (
Bünning led the Lapland field trips until 1969 at the age of 63 and together with a colleague until 1980. The Lapland excursions became so popular that they are still going on. A 60-year Lapland Festival was held in 2010 at the University of Tübingen.
The Private Bünning
We have reported about our many experiences and interactions with our professor, but there is much more to tell about Bünning’s unique style of interacting with his students. He seemed to be inaccessible, walking through the halls of his institute with his head bent and arms folded in the back. However, if we needed him for personal advice, we experienced the most empathetic person. Each of his students could pitch in here with a personal story. He was, for all of us, a true “Doktorvater.”
Not only could we come to him, but Bünning also dropped by our office from time to time to talk about his ideas and plans. One day he took me to the location where a new botanical garden, the Palm House, and the science buildings would be erected soon (he had been critically involved in the planning phase of this new science center). He overlooked the place quite happily and pointed out where the new buildings would rise up. This is one example of how he integrated us into his plans and visions.
After lunch in the university cafeteria, a group of us usually walked through the botanical garden to our labs. Following a substantial snowfall, we were tempted to test who was best in hitting a target. We chose the head of a sculpture of the much-revered and famous Tübingen poet, Friedrich Hölderlin. While we were in the middle of the competition, a middle-aged person walked by asking us to stop immediately because we disgraced the sculpture. He also asked each of us to tell him our names and wrote them down. The person promptly reported us to Bünning, who asked us to show up immediately at his office. He smiled upon hearing our account of what happened and said that in such an unimportant case, we should never, ever tell anybody our names if asked.
Bünning’s house was a place that we could always visit. When I was alone taking care of the research projects of my fellow graduate students over Christmas break in 1961, my first Christmas far from home, Bünning and his wife invited me to their home for dinner. From then on, I, often accompanied by other PhD students, was always welcome. When we arrived, there was juice, wine, and salt sticks at the table within a few seconds, and we were sitting and talking on different topics: scientific, political, and sometimes personal. His wife Eleonore was always actively involved. Very special were the invitations when Bünning himself cooked for us. Walter, you remember these evenings especially well.
Yes, one of the highlights was when Bünning cooked rice for us. He did this in the Indonesian style with hot spices, which he had learned from his travels in Sumatra. He used it as a test of who could eat his food without crying. He often talked about these travels and provided practical tips for jungle trips.
At one point in these gatherings, Bünning asked us what professional goal we had. We looked at each other but were too shy to confess that we wanted to become a professor—as he had, our great example. Some of us around the table actually reached this goal; others became outstanding high school teachers. One, Ernst Waldemar Bauer, became a famous TV host. Bünning kept reminding us that in order to reach our goals, we needed to focus on excellence. He addressed me after my PhD exam and said, “You must decide whether you want to have a family and children or to commit fully to your profession, being a scientist and teacher.” This view has certainly changed today.
Here is an account of how Bünning challenged students to think unconventionally. One of the associated professors in the Botanical Institute, Wolfgang Haupt, told us about a student asking for a topic for a PhD thesis. It was in the 1950s, the time when the experimental foundation for the importance of photo- and thermoperiodicity for seed germination was developed. Bünning challenged the student to heat seeds to 110°C and observe what would happen. This suggestion was the basis for an interesting new discovery.
Our inability to communicate fluently in English was a constant theme at the table. He challenged us in his own way to speak the language. For example, one afternoon he asked me and the graduate student who shared my office to pick up an Indian from the train station in the evening, which we did successfully but only because the visitor could speak some German. At one of the usual invitations to his house, over Indonesian rice, Bünning suddenly changed the topic from the importance of mastering the English language and mentioned that it would be equally important to learn Chinese because the Chinese would, sooner or later, have a dominating influence in the world. What a prophetic prediction but also provocative, typical for him.
Even more provocative was Bünning’s prediction with respect to the future relationship between China and Europe. He expressed his opinion as a drastic picture: in the past and until then, Europeans went to China as masters on the roads, and the Chinese were sitting at the roadside to beg for a morsel; but in the future, it would be the opposite, with the Chinese going to Europe as masters on the roads, and the Europeans sitting at the roadside and begging for alms.
This reminds me of a story pertaining to his admiration of the Chinese people. One of our co-PhD students, Claus Schilde, presented Bünning with a “Mao bible,” as we called the teachings of Mao Zedong, as a gift. Bünning opened the drawer of his desk, pulled out his own copy, saying, “I have it already, give it to somebody else.” This occasion exemplifies why we revered him. He was not the usual stuffy German Ordinarius. He displayed a unique humor.
Speaking about humor and nonconformity: in 1967, after the completion of the move from the old Botanical Institute to the new Institute of Biology, built according to his ideas, Bünning fixed an old envelope folder on the door of his old office on which he wrote with a thick felt pen, “This store has gone bankrupt. Therefore I’ll leave for two weeks to the a. . . of the world, 69° northern latitude, instead of +37°C. Clients are asked to contact the new competing company: Institute of Biology, Tübingen, Auf der Morgenstelle, Bü.” I still have the photo of this posting.
While talking about the “private Bünning,” we should not forget an occurrence that hit him and his wife, and certainly their 3 other children, very hard. They were devastated by the death of their oldest and very gifted son as the result of a climbing accident in the Italian Dolomites. They received the message while they were hiking in Lapland. Bünning never talked much about it, but I sometimes sensed his grief when we talked about children.
Bünning saw me sometimes leaving with my motorcycle to go rock climbing for several hours with a friend in the mountain range close by to clear my head. He came one day to my office to remind me of the dangers of rock climbing. As I wondered why he cared, he told me the story of how his son had died in one of the extremely difficult ascents on the south face of the Marmolata. Surprised by a blizzard, his partner fell and both froze to death overnight as Bünning’s son tried to save him, even though he was already beyond the most difficult part of the route and could have continued on.
Final Note
As we were wrapping up our exchange of memories, it was past midnight, and the owner notified us that soon he would close the Weinstube. We reminded each other that it had been almost 60 years ago that we had interacted with Bünning and only thanks to talking with each other had the many details from that time come to light. We wondered how many of the current generation of scientists conducting rigorous research in the field of circadian rhythms would remember the name of this ground-breaking pioneer as well as of his colleagues Aschoff and Pittendrigh.
Footnotes
Acknowledgements
We are grateful to William Schwartz for encouraging us to write down our experiences with Erwin Bünning and moreover for his help in bringing this article to its final form. Thanks also to Marianne Bentley for editing the English text and to Ilse Franklin and Ingrid Hancke, Bünning’s daughters, who contributed personal memories for the introduction. Manfred Grohe photography, Am Sonnenrain 34, 72138 Kirchentellinsfurt, Germany, gave permission to publish his portrait of Bünning in Figure 1.
Conflict of Interest Statement
The authors have no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.