Saussure, Nicholas Théodore de (1767–1845)

Swiss botanist, chemist, and plant physiologist who established the discipline of phytochemistry (the study of the chemistry of plants) and showed that plants gain weight during photosynthesis. He also studied the formation of carbonic acid in plants.

His most important research was in the area of photosynthesis. In 1804, he demonstrated that plants gain weight by converting carbon dioxide to oxygen. Originally, he concluded correctly that this reaction was dependent upon light and incorrectly that carbon and oxygen were the products formed from the carbon dioxide. However, he later realized that more weight was gained than was due to the carbon, and he deduced that water must also be incorporated into the plant's dry weight.

Saussure was born in Geneva, the son of a scientist who chose to educate his son himself. They made several scientific expeditions together, ascending Mont Blanc 1787 and conducted experiments that confirmed the work of Edmé Mariotte on the weight of air at various altitudes. Saussure developed an interest in botany, especially plant physiology, during these alpine expeditions. In 1797, he published several papers on the formation of carbonic acid in plants.

In 1802, he was made professor of mineralogy and geology at Geneva. Despite holding this position until 1835, he never delivered any lectures as he had wanted a position in plant chemistry. He continued with his botanical research, writing Recherches chimiques sur la vegetation 1804, which established the discipline of phytochemistry.