De Saussure, Nicolas-Théodore
Swiss Botanist 1767-1845
Nicolas-Théodore de Saussure was one of the early founders of plant physiology. He introduced new and rigorous experimental methods to the study of plants, and his work helped to improve the science of botany.De Saussure was born in Geneva, Switzerland, on October 14, 1767. His father, Horace-Bénédict de Saussure (1740-1799), was also a scientist and he supervised his son's early experiments. Nicolas-Théodore accompanied his father on many expeditions to the tops of mountains to study the composition and density of air, and he made many weather and air measurements on these trips with his father in the Alps. This research led to his appointment as a professor of mineralogy and geology at the Geneva Academy.
At this time de Saussure had become interested in plant physiology, particularly in the way that plants use air. In 1804 he published his most famous work, Recherches chimiques sur la végétation. This collection of classic research papers introduced a new scientific method to the study of botany. His experiments were very carefully designed to address specific questions rather than to just make a series of observations. He also carefully controlled the experiments and repeated them to make sure his results were accurate. His detailed method of experimenting became the foundation for current plant science.
With this new scientific approach, de Saussure was able to demonstrate conclusively what others had long suspected. His first experiments concerned photosynthesis and respiration in plants. In one experiment, he enclosed plants in glass containers and used these containers to control the level of carbon dioxide available to the plants. After placing the plants in the light for a few hours, he measured changes in air composition in the containers and carbon accumulation in the plants. In this way, he showed that the plants had taken up the carbon dioxide and given off oxygen. In addition, he showed that carbon dioxide came from the air, not from water, as some other scientists believed. This and other similar experiments using different concentrations of oxygen and carbon dioxide and different light conditions helped him understand the basis of photosynthesis: that plants in the light are able to fix carbon in their tissues while giving off oxygen. He also correctly believed that plants used oxygen to respire in the same way as animals. He had first noted this need for oxygen in germinating seeds and plants grown in the dark. These beginning studies of respiration and photosynthesis and his later studies of plant nutrition became part of the new scientific study of plant physiology.
After this initial work, de Saussure went on to study the content of fruits and seeds and to use the ash of burned plants to examine other nutrients and minerals that plants required. Among other discoveries, he showed that plants take up nutrients from the soil selectively. His life work became a large survey of plant nutrition and, at the same time, it established a higher standard of plant scientific method. By the time de Saussure died in Geneva on April 18, 1845, he had received many honors and had become a member of many European scientific societies.
Atmosphere and Plants; Hales, Stephen; Photosynthesis, Carbon Fixation And; Physiologist; Physiology, History Of.
Bibliography
Morton, A. G. History of Botanical Science. New York: Academic Press, 1981.
Sachs, Julius von. History of Botany, tr. Henry E. F. Garnsey. New York: Russel and Russel, 1967.
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