Pfeffer, Wilhelm (vĭlˈhĕlm pfĕˈfər) [key], 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).
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