Wilhelm Pfeffer

Wilhelm Friedrich Philipp Pfeffer (9 March 1845 - 31 January 1920) was a German botanist and plant physiologist born in Grebenstein.

Academic career

He studied botany, physics and pharmacology at the University of Göttingen under Friedrich Wöhler (1800-1882), William Eduard Weber (1804-1891) and Wilhelm Rudolph Fittig (1835-1910). Afterwards he furthered his education at the Universities of Marburg and Berlin. At Berlin he studied under Alexander Braun (1805-1877) and was an assistant to Nathanael Pringsheim (1823-1894). He later worked as an assistant to Julius von Sachs (1832-1897) at Würzburg, and in 1873 became a professor of pharmacology and botany at the University of Bonn. Later he worked as a professor at the Universities of Basel (from 1877) and Tübingen (from 1878), where he was director of the Botanischer Garten der Universität Tübingen. In 1887 he became a professor at the University of Leipzig, where he also served as director of the Leipzig Botanical Garden.

He was elected a member of the Royal Swedish Academy of Sciences in 1897.

Scientific work

Pfeffer was a pioneer of modern plant physiology. His scientific interests included the thermonastic and photonastic movements of flowers, the nyctinastic movements of leaves, protoplastic physics and photosynthesis. In 1877, while researching plant metabolism, Pfeffer developed a semi-porous membrane to study the phenomena of osmosis. The eponymous "Pfeffer cell" is named after the osmometric device he constructed to determine the osmotic pressure of a solution.

During his tenure at Leipzig, Pfeffer published an article on the use of photography to study plant growth. He wanted to extend the chronophotographic experiments of Étienne-Jules Marey (1830-1904) by producing a short film involving the stages of plant growth. This "movie" would be filmed over a period of weeks by frame-at-a-time exposure taken at regular spaced intervals. Later, time-lapse photography would become a commonplace procedure.

Pfeffer cell

The Pfeffer cell determines the osmotic pressure of a solution.   The Pfeffer cell was composed of a porous earthenware container, with a copper ferrocyanide precipitate, connected to a manometer.

Written works

• Physiologische Untersuchungen - 1873 (Physiological studies)
• Lehrbuch der Pflanzenphysiologie (Textbook of Plant Physiology).
• Die periodischen Bewegungen der Blattorgane - 1875 (The periodic movements of "leaf organs")
• Beiträge zur Kenntniss der Oxydationsvorgänge in lebenden Zellen - 1889 (Contributions to the knowledge of the oxidative processes in living cells).
• Über Aufnahme und Ausgabe ungelöster Körper - 1890
• Studien zur Energetik der Pflanze - 1892 (Studies on the energetics of plants)
• Druck- und Arbeitsleistung durch wachsende Pflanzen - 1893
• Untersuchungen über die Entstehung der Schlafbewegungen der Blattorgane - 1907
• Der Einfluss von mechanischer Hemmung und von Belastung auf die Schlafbewegung - 1911 (The influence of mechanical stress on the inhibition of sleep and movement).
• Beiträge zur Kenntniss der Entstehung der Schlafbewegungen- 1915 (Contributions to the knowledge on the genesis of sleep movements).
• Osmotische Untersuchungen, second unveränd. edition- 1921 (Osmotic studies).

References

• List of publications copied from an equivalent article at the German Wikipedia.