Courtesy of the University of Illinois Archives
Robert Emerson was born on November 3, 1903 in New York City. He received his M.Sc. from Harvard in 1925. He later became interested in plant physiology, and traveled to Germany to work under Otto Warburg, a leading scientist studying photosynthesis. Emerson received a Ph.D. in Botany from the University of Berlin and started his work at CalTech, where he made multiple revolutionary discoveries in photosynthesis research. His first major contribution was the discovery of the photosynthetic unit - that 2400 chlorophyll molecules can only reduce one molecule of oxygen. In 1937, Emerson and physicist Charleton Lewis came to Carnegie’s Plant Biology department in Stanford to study the quantum yield of photosynthesis. Emerson and Lewis discovered that 8 quanta of light are required to reduce one molecule of oxygen, meaning that photosynthesis is much less efficient than originally thought. This discovery directly challenged his former advisor Warburg's work. At Carnegie, he also discovered a significant drop in the rate of photosynthesis at far-red wavelengths, referred to as the "red drop" in photosynthesis. His findings later led to the discovery of two photosystems in photosynthesis. After returning to CalTech in 1940, he studied the action spectrum of photosynthesis, discovering photosynthetic roles of many accessory pigments.