Daniel Israel Arnon was a Polish-born American plant physiologist whose research led to greater insights into the operation of photosynthesis in plants. In 1973, he was awarded the National Medal of Science for "his fundamental research into the mechanism of green plant utilization of light to produce chemical energy and oxygen and for contributions to our understanding of plant nutrition." He discovered the essentiality of molybdenum for the growth of all plants and of vanadium for the growth of green algae. Arnon was born on November 14, 1910, in Warsaw, to a Jewish family. Summers spent on the family's farm helped foster Arnon's interest in agriculture. His father had lost the family's food wholesale business after World War I and Arnon's readings of the works of Jack London led him to save up his money to head to California. He enrolled in the University of California, Berkeley, from Poland, and would spend his entire professional career at the school, until his retirement in 1978. He ultimately earned his Ph.D. in plant physiology in 1936 at UC Berkeley under Dennis R. Hoagland and some of his earliest research focused on growing plants in nutrient-enriched water rather than in the soil. Together with his supervisor he refined the Hoagland solution published in 1938. During World War II, Arnon served in the United States Army in the Pacific Theater of Operations where he used his prior experience with plant nutrition on Ponape Island, where there was no arable land available, and he was able to grow food to feed the troops stationed there using gravel and nutrient-enriched water. After returning from military service, Arnon performed research on chloroplasts and their role in the photosynthesis process. His work was able to demonstrate how energy from sunlight is used to form adenosine triphosphate, the energy transport messenger within living cells, by adding a third phosphorus group to adenosine diphosphate. In 1954, Arnon reproduced the process in a laboratory, making him the first to successfully demonstrate the chemical function of photosynthesis, producing sugar and starch from inputs of carbon dioxide and water. He was elected a Fellow of the American Academy of Arts and Sciences in 1962. A resident of Kensington, California, Arnon died at age 84 on December 20, 1994, in Berkeley, California, of complications resulting from cardiac arrest. He had three daughters and two sons. His wife, the former Lucile Soule, died in 1986.
