SAUSSURE, NICOLAS-THéODORE DE

(b. Geneva, Switzerland, 14 October 1767; d. Geneva, 18 April 1845)

chemistry, plant physiology.

Saussure was the son of the scientist Horace-Bénédict de Saussure (1740–1799) and Albertine-Amélie Boissier. His father supervised his initial studies and Saussure aided his father in his research. During the famous ascent of Mont Blanc on 3 August 1787, Nicolas was assigned by his father to make all the meteorological and barometric observations. In 1788 Nicolas accompanied his father on the expedition to the Col du Géant. They remained for seventeen days and nights in the snow fields.

During other expeditions, Saussure made observations on the composition of the atmosphere, the density of the air, and the geodesic features of the area around Geneva. In July 1789 he climbed Monte Rosa, where he pursued his experiments on the weight of the air. Using new techniques, he corroborated, with great precision, the observations of Mariotte, which had given rise to the Boyle-Mariotte law.

At this time Saussure became passionately interested in chemistry and in plant physiology, and he accumulated original observations, particularly on the mineral nutrition of plants. He later published this work. When the Revolution broke out, Saussure left Geneva for England. He returned in 1802 to occupy a promised chair in plant physiology at the Geneva Academy. Instead, he was named honorary professor of mineralogy and geology, a title he held until 1835. Disappointed at not being able to teach plant chemistry, the subject that had absorbed his attention since his first publication in 1797, he requested a leave of absence several days after his nomination. He never gave a course at the Academy.

In 1797, in Annales de Chimie, Saussure published three remarkable articles on carbonic acid and its formation in plant tissues. These works, followed in 1800 by an important study of the role of soil in the development of plants, brought him the recognition of his fellow scientists.

Saussure published his Recherches chimiques sur la végétation in Paris in 1804. An immediate success, it was translated into German in 1805 by F. S. Voigt and went through many editions. This work, which took seven years to write, laid the foundations of a new science, phytochemistry. Saussure examined the chief active components of plants, their synthesis, and their decomposition. He specified the relationships between vegetation and the environment and here, too, did pioneering work in what became the fields of pedology and ecology.

Starting in 1808, Saussure published a series of important articles, most of them devoted to a rigorous analysis of biochemical reactions occurring in the plant cell. The first dealt with the phosphorus content of seeds (1808). Then came two works on the conversion of starch into sugars by the action of air and water (1814 and 1819). These were followed by a study of the oil stored in fruits (1820). Saussure also investigated the biochemical processes that take place during the maturation of fruits (1821) and flowers (1822). Later he turned to the chemistry of germination and was the first to note the influence of desiccation on several food grains (1826). He then examined the formation of sugar during the germination of Wheat (1833) and compared germination to fermentation reactions (1833). Several of the publications in which he reported his analysis of fermentation were regarded highly by Pasteur.

Saussure next studied the action of fermentation on the oxygen and hydrogen of air (1839) and also alcoholic fermentation (1841). Toward the end of his life, he took up again his research on plant nutrition (1841). His last paper was on the germination of oilseeds (1842).

Saussure received many honors. He was named a corresponding member of the Institut de France (1805), member of the Conseil Représentatif de Genève (1814), and was a founding member of the Société Helvétique des Sciences Naturelles (1815). By 1825 he was an associate member of virtually all the great European academies, and in 1842 he was elected president of the Congrés Scientifique of Lyons. In 1837 A. P. de Candolle named a genus of composite flower Saussurea and a section of the genus Theodora.

BIBLIOGRAPHY

I. Original Works. Saussure’s works include “Essai sur cette question: La formation de l’acide carbonique est-elle essentielle à la végétation?” in Annales de chimie. 24 (1797), 135–149, 227–228, 336–337; Recherches chimiques sur la végétation (Paris, 1804); “Sur le phosphore que les graines fournissent par la distillation et sur la décomposition des phosphates alcalins par le carbone,” in Annales de chimie, 65 (1808), 189–201; “Observations sur la décomposition de l’amidon à la température atmosphérique par l’action de l’air et de l’eau,” ibid., 11 (1819), 379–408; “Observations sur la combinaison de l’essence de citron avec l’acide muriatique et sur quelques substances huileuses,” in Archives des sciences physiques et naturelles. 13 (1820), 20–42, 112–135; “De l’influence des fruits verts sur l’air avant leur maturité,” in Mémoires de la Société de physique et d’histoire naturelle de Genève. 1 (1821), 245–287; “De l’action des fleurs sur l’air, et de leur chaleur propre,” in Annales de chimie et de physique, 21 (1822), 279–304; “De l’influence du dessèchement sur la germination de plusieurs graines alimentaires,” in Mémoires de la Société de physique et d’histoire naturelle de Genève. 3 (1826), 1–28; “De la formation du sucre dans la germination du froment,” ibid., 6 (1841), 239–256; “Faits relatifs à la fermentation vineuses,” in Archives des sciences physiques et naturelles, 32 (1841), 180–256; and “Sur la nutrition des végétaux,” ibid., 36 (1841), 340–355.

II. Secondary Literature. On Saussure and his work, see C. Borgeaud, Histoire de l’Université de Genève, II (Geneva, 1909), 83; J. Briquet, “Biographies des botanistes à Genève de 1500 à 1931,” in Bericht der Schweizerischen botanischen Gesellschaft. 50 (1940). 425–428; M. Macaire, “Notice sur la vie et les écrits de Théodore de Saussure,” in Bibliothèque universelle de Genève, Nouvelle série, 57 (1845).

P. E. Pilet

De Saussure, Nicolas-Théodore

Swiss botanist 1767–1845

Nicolas de Saussure was an early pioneer in plant physiology. He was born and lived in Geneva, Switzerland, and later became professor of mineralogy and geology at the Geneva Academy. De Saussure's most famous book was Recherches chimiques sur la végétation, or "Chemical Research on Plant Matter," published in 1804.

De Saussure studied gas and nutrient uptake in plants, using the scientific method of controlled experimentation. By enclosing plants in glass containers and weighing the plants and enclosed carbon dioxide before and after, de Saussure demonstrated that plants absorb carbon dioxide during photosynthesis. This showed that carbon in plants comes from the atmosphere (not the soil, as some believed). Extending the work of Jan Ingenhousz, who showed oxygen was released during photosynthesis, de Saussure proved that the volume of carbon dioxide absorbed is approximately equal to the volume of oxygen consumed. Because the weight of carbon absorbed was less than the total weight increase of the plant, de Saussure reasoned that water is absorbed, and in so doing correctly outlined the major chemical transformations in photosynthesis.

De Saussure also studied oxygen consumption in germinating seeds and plants grown in the dark, and argued (correctly) that the use of oxygen by plants was similar to that of animals. Later in life, he analyzed plant ashes to show that the mineral composition differed from that of the soil, thereby demonstrating that plants absorb nutrients selectively.

see also van Helmont, Jan; History of Plant Physiology; Ingenhousz, Jan; Photosynthesis

Richard Robinson

Bibliography

Morton, Alan G. History of Botanical Science. New York: Academic Press, 1981.

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.

see also Atmosphere and Plants; Hales, Stephen; Photosynthesis, Carbon Fixation and; Physiologist; Physiology, History of.

Jessica P. Penney

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.