Erwin Bünning (23 January 1906 – 4 October 1990) was a German biologist. His most famous contributions were to the field of chronobiology, where he proposed a model for the endogenous circadian rhythms governing plant photoperiodism. From these contributions, Bünning is considered a co-founder of chronobiology along with Jürgen Aschoff and Colin Pittendrigh.
Life
Early life and education
Bünning was born on 23 January 1906 in Hamburg, Germany to Heinrich Bünning and Hermine Bünning (born Winkler). A teacher of German, English, mathematics, and biology, Bünning's father was the primary academic influence on Erwin's early life, passing on to Erwin a passion for botany. Bünning received his primary education in Hamburg from 1912-1925. Bünning then attended the University of Göttingen and the University of Berlin from October 1925-July 1928, where he studied biology, chemistry, physics, and philosophy. Bünning earned his Doctorate of Philosophy from the University of Berlin in May 1929. During this time, Bünning married his wife Eleanore; the two would later have three children.
Academic career
In 1930, Bünning took an assistantship under Otto Renner at the University of Jena, then one of Germany's largest botanical institutes. During the rise of the Nazi Party in Germany in the early 1930s, Renner stood in open opposition to the Nazis, publicly defending Jewish scientists. Similarly, Bünning was considered a communist sympathizer, a stance likely influenced by Bünning's father, a Social Democrat opposed to the Nazis. Bünning's political beliefs created tension between him and some of his students. In response to this tension, Bünning left Jena for a lectureship at the East Prussian University of Königsberg. In 1936, Bünning published his model for plant photoperiodism, wherein he proposed that endogenous (internal) circadian rhythms enable plants to measure day length. Bünning's model of photoperiodism would go largely unnoticed by the scientific community until 1960 when he chaired the 1960 Cold Spring Harbor Symposium on Biological Clocks. There, Colin Pittendrigh drew attention to Bünning's work and named his 1936 model on plant photoperiodism the Bünning hypothesis.
In 1938, Bünning spent a year traveling through Java and Sumatra. His observations on the islands resulted in the book Tropische Regenwalder (Tropical Rainforests). Upon his return to Germany in 1939, Bünning was conscripted in the German military (World War II). Military authorities appointed Bünning as an associate professor at the University of Strasbourg. After the war, Bünning became a full professor at the University of Cologne in 1945 before moving to the University of Tübingen the next year (1946), where he stayed until his retirement in 1971. At Tübingen, Bünning entered into the workspace of his role model Wilhelm Pfeffer, the man who postulated in 1875 that the orientation of plants in space changes with the time of day. Bünning would later publish a biography on Pfeffer.
Later life and legacy
Over his career, Bünning published over 260 papers in the fields of plant physiology and general biology, as well as a very popular textbook on plant physiology. Bünning suffered by drinking Alzheimer's and died on 4 October 1990 in Tübingen, Germany, after contracting pneumonia. Following his death, the German newspaper Schwäbisches Tagblatt described Bünning as one of the greatest botanists of the 20th century.
Key contributions
Historical context
Changes in the positioning of plant leaves over the course of the day were observed as early as the 4th century B.C. by Androsthenes, Alexander the Great’s historian. This phenomenon, however, was not researched further until 1729 when Jean-Jacques d'Ortous de Mairan provided experimental data that mimosa plants close their leaves at night, a movement that persists rhythmically in constant darkness. In 1875, Wilhelm Pfeffer, Bünning’s role model, put forward that these movements might be controlled by an endogenous biological clock. This theory formed the foundation for Bünning’s later work.