Pfeffer, Wilhelm(vĭl`hĕlm pfĕ`fər), 1845–1920, German plant physiologist. He was professor of botany successively at the universities of Bonn, Basel, Tübingen, and Leipzig (from 1887). With Julius von Sachs, he was a leader in systematizing the fundamentals of plant physiology. Pfeffer's experiments in osmotic pressure were fundamental to modern physical chemistry. He wrote a standard work, Physiology of Plants (1881, tr. 1900–1906).
Born Mar. 9, 1845, in Grebenstein, near Kassel; died Jan. 31, 1920, in Leipzig. German botanist.
Pfeffer, who graduated from the University of Göttingen in 1865, was a professor at the universities of Bonn (1873), Tübingen (1878), and Leipzig (1887). His work was largely devoted to osmosis and its role in the absorption, transfer, and evaporation of water in plants. He also studied the role of osmosis in the mineral nutrition of plants. Pfeffer’s works included studies of plant respiration, photosynthesis, nitrogen exchange, and irritability. He discovered positive chemotaxis in the spermatozoids of ferns.