Dr Erwin Bünning (23 January 1906 – 4 October 1990) was a German biologist. His pioneering research in botany and plant physiology resulted in several contributions in phototropism, phototaxis, differentiation, growth substances and even Tropical Forests. He made his most famous contributions in the area of chronobiology.
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Bünning was born in Hamburg to Heinrich Bünning, a school teacher, and Hermine Winkler. His father taught German, English, Mathematics and Biology. A firm Social Democrat opposed to the Nazis, he was the earliest academic influence in Erwin's life. Erwin Bünning studied Biology, Chemistry, Physics and Philosophy, at the Universities of Berlin and Göttingen, between October 1925 and July 1928, and earned his Doctorate of Philosophy in May 1929 from Berlin. He became a Scientific Assistant in the University of Jena in 1930. Tensions with students active in the Nazi movement caused him to move to a lectureship in the East Prussian University of Königsberg.
Bünning travelled to Java and Sumatra in 1938 for a year. His observations on the islands resulted in the book Tropische Regenwalder (Tropical Rainforests). When he returned to Germany, he was conscripted into the army. During World War II, he was appointed Reader at the University of Strasbourg. After the war, he became a professor at the University of Cologne in 1945. He moved to the University of Tübingen the next year, where he stayed until 1971, when he retired on his 65th birthday. He published over 260 papers in various fields of plant physiology and general biology, as well as a very popular text book on plant physiology. He also wrote a biography of Wilhelm Pfeffer.
Bünning married Eleanore, and they had three children.
Bünning suffered from Alzheimer's Disease, and died on 4 October 1990, after contracting pneumonia. Writing about his death, the German newspaper Swabisches Tagblatt described him as one of the greatest botanists of the 20th century.
In the early-1930s, Bünning proposed that a circadian rhythm of sensitivity to light was being used to measure how much daylight was "encroaching" into the night-time, thus measuring the photoperiod. He demonstrated that plants and insects behaved according to circadian rhythms, whether or not they were in continuous light or darkness. His crossing experiments with bean plants of different periods in 1932 demonstrated that the next generation had periods of intermediate durations, supporting the suggestion that circadian rhythms are heritable. In 1935, Erwin Bünning determined in plants the genetic origin of the "biological clock," a term he coined. It took at least a decade of experimental work by Bunning and others for this proposal, called the Bünning Hypothesis, to get firmly accepted by chronobiologists.
Chronobiology investigates biological rhythms occurring in some prokaryotes and in all eukaryotes from fungi to humans. The most common of these rhythms, called Circadian rhythms or Biological Clocks, have a periodicity of 24 hours.
Bünning chaired the now famous meeting on Biological Clocks at the 25th Cold Spring Harbor Symposium in 1960, convened by Colin Pittendrigh. He was elected Corresponding Member of the Botanical Society of America in 1961. He won the Charles Reid Barnes Life Membership award of the American Society of Plant Biologists in 1973.
The universities of Glasgow (1974), Freiburg (1977), Erlangen (1977) and Göttingen (1986) conferred honorary doctorates on him. He was a Member of the Deutsche Akademie der Wissenschaften, Berlin, Leopoldina, Halle, Heidelberger Akademie der Wissenschaften, Bayerische Akademie der Wissenschaften, National Academy of Sciences, USA, Washington, Foreign Member of the Royal Society of London and an Honorary Fellow of the Indian Academy of Sciences.