On September 9, 1841, Swiss botanist Augustin Pyramus de Candolle passed away. Candolle originated the idea of “Nature’s war”, which influenced Charles Darwin and the principle of natural selection. Furthermore, he recognized that multiple species may develop similar characteristics that did not appear in a common evolutionary ancestor; this was later termed analogy. During his work with plants, de Candolle noticed that plant leaf movements follow a near-24-hour cycle in constant light, suggesting that an internal biological clock exists.
Augustin Pyramus de Candolle studied science Collège at the Calvin under Jean Pierre Étienne Vaucher. It is believed that Vaucher inspired de Candolle to make a career in botanical science. In 1798, he moved to Paris and he started working in the herbarium of Charles Louis L’Héritier de Brutelle. Through this position, de Candolle was able to establish a good reputation. After publishing his first major works, Plantarum historia succulentarum and Astragalogia, he was noticed by Georges Cuvier as well as Jean-Baptiste Lamarck. The latter then entrusted him with the publication of the third edition of the Flore française and in the introduction entitled Principes élémentaires de botanique, de Candolle proposed a natural method of plant classification as opposed to the artificial Linnaean method. In 1804, de Candolle published his Essai sur les propriétés médicales des plantes and was granted a doctor of medicine degree by the medical faculty of Paris. de Candolle was appointed professor of botany in the medical faculty of the University of Montpellier, where he would later become the first chair of botany in 1810. Seven years later he was invited by the government of the Canton of Geneva to fill the newly created chair of natural history.
In the field of chronobiology, de Candolle built upon earlier work on plant circadian leaf movements contributed by such scientists as Jean-Jacques d’Ortous de Mairan and Henri-Louis Duhamel du Monceau. He observed in 1832 that the plant Mimosa pudica had a free-running period of leaf opening and closing of approximately 22–23 hours in constant light, significantly less than the approximate 24-hour period of the Earth’s light-dark cycles. He hypothesized that a different clock had to be responsible for the rhythm. The shortened period was not entrained—coordinated—by environmental cues, thus the clock appeared to be endogenous. In the mid-1920s, Erwin Bunning repeated Candolle’s findings and came to similar conclusions, and studies that showed the persistence of circadian rhythm in the South Pole and in a space lab further confirmed the existence of oscillations in the absence of environmental cues.
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