Jan Ingenhousz: The Man Who Discovered Photosynthesis

Today, Google is celebrating the 287th birthday of Jan Ingenhousz. While you may not be familiar with the name, you almost certainly learned about his most famous finding in your junior-high science class.

Ingenhousz, a Dutch physician born in 1730, discovered photosynthesis—how plants turn light into energy. In this process, chlorophyll in plant cells absorbs light and uses it to convert atmospheric carbon dioxide and water to sugars, which the plants consume for energy. The cells give off oxygen as a byproduct of the whole cycle.

Previous research by the English chemist Joseph Priestley had revealed that plants produce and absorb oxygen from the atmosphere, and after meeting Priestley in 1771, Ingenhousz conducted further experiments on plants' physiology. He saw that green plants released bubbles of oxygen in the presence of sunlight, but the bubbles stopped when it was dark—at that point, plants began to emit some carbon dioxide. Ingenhousz concluded that light was necessary for these steps to take place. He also found that plants give off far more oxygen than carbon dioxide, thus identifying the benefits of having greenery around to purify the air.