Erwin Bünning
His most famous contributions were to the field of chronobiology, where he proposed a model for the endogenous circadian rhythms governing plant photoperiodism.
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.
[2] 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.
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.
[5] In 1875, Wilhelm Pfeffer, Bünning’s role model, put forward that these movements might be controlled by an endogenous biological clock.
He demonstrated that plants open and close their leaves and insects eclose according to circadian rhythms, even in continuous light or darkness.
[9] Bünning also demonstrated that an artificial photoperiod can induce flowering at inappropriate times, supporting his model of endogenous oscillators entrained to external stimuli.
To create artificial photoperiods, Bünning exposed plants to a light-dark cycle indicative of a specific season, such as the long days and short nights of summer.
By entraining the plants to a spring or summer photoperiod, Bünning was able to induce flowering, even if the actual season were fall or winter.
[8][10] From his results, Bünning proposed that biological clocks have sensors for both light and dark, and their relationship aids photoperiodic timekeeping.
[11] His published works provided key synthesis of existing evidence for biological clocks across species, including plants, flies, and fungi.
As day length increases with the spring and summer seasons, for example, light hits a plant's photosensitive phase, triggering a physiological or behavioral response.
[2] In 1973 Bünning won the Charles Reid Barnes Life Membership Award[18] for "meritorious work in plant biology.
