Melvin Calvin, the University of California, Berkeley, professor who won the Nobel Prize in chemistry in 1961 for his analysis of the photosynthesis of plants, has died. He was 85.

Calvin, called “Mr. Photosynthesis” after winning the Nobel, died Wednesday at a Berkeley hospital. His health had been declining for several years.

Calvin’s findings prodded the U.S. Department of Energy to pursue solar energy as a source of power.