He enlisted in the Marines during World War II and served in the Pacific as defense counsel in courts-martial for soldiers who were charged with being AWOL.
After his discharge, Leopold received MS and PhD degrees in plant physiology from Harvard University, studying under Kenneth Thimann.
In 1977, Leopold moved to the Boyce Thompson Institute for Plant Research (BTI) in Ithaca, New York as William H. Crocker Scientist.
Seeds such as soybeans containing very high levels of protein can undergo desiccation, yet survive and revive after water absorption.
He found soybeans and corn to have a range of soluble carbohydrates protecting the seed's cell viability by forming a glassy state rather than drying completely.