Jan Ingenhousz

Today is the birthday of Jan Ingenhousz, the Dutch scientist who discovered photosynthesis. He was born in Breda, Netherlands in 1730. Ingenhousz was a man of many scientific talents. He was a respected physician who advocated inoculation against smallpox using live virus taken from patients with mild symptoms. In 1768 he was summoned to Vienna to inoculate Austrian empress Maria Theresa and her family. Ingenhousz later studied static electricity and heat conduction. But his most famous contribution was detailed in his 1779 paper, “Experiments Upon Vegetables, Discovering Their Great Power of Purifying the Common Air in Sunshine, and of Injuring It in the Shade and at Night.” He discovered that plants, specifically their green-colored components, release a combustible gas (oxygen) when exposed to light—a process later termed photosynthesis. At night plants emitted a different gas (carbon dioxide), though not in abundance. Though plants do respire and convert oxygen to carbon dioxide, that is overcome by their ability to perform photosynthesis and release oxygen into the air.

Date in History: 8 December 1730