Nicolas Théodore de Saussure

Born Oct. 14, 1767, in Geneva; died there Apr. 18, 1845. Swiss naturalist. Corresponding member of the Paris Academy of Sciences (from 1808), professor at the Geneva Academy (from 1802), fellow of the Royal Society of London (from 1820). Son of H. B. de Saussure.

Saussure is known primarily for his research in plant physiology, although he also did work in physics, chemistry, and geology. He was the first naturalist to apply accurate methods of quantitative chemical analysis to the study of gas exchange and mineral assimilation by plants. Saussure demonstrated experimentally that although respiration in plants proceeds as it does in animals, with the absorption of oxygen and the elimination of CO₂, in the presence of light plants assimilate the carbon from CO₂. He also demonstrated that minerals in the soil enter plants through the roots.