Julius von Sachs (German: [zaks]; 2 October 1832 – 29 May 1897) was a German botanist from Breslau, Prussian Silesia. He is a monumental figure in the history of botany.
Sachs was born at Breslau on 2 October 1832. His father, Graveur Sachs, was an engraver by trade, and father taught son delineation and accuracy of line and color. From earliest boyhood Julius was fascinated with plants, making collections of them on many field excursions with his father. He gave much of his time between the ages of thirteen and sixteen to drawing and painting the flowers, fungi, and other specimens which he collected. At the Gymnasium from 1845 to 1850 he was most interested in the natural sciences, collecting skulls, writing a monograph on the crayfish. His natural science teacher, one Krober, showed a singular lack of foresight when he solemnly warned young Sachs against devoting himself to the natural sciences.
When he was but sixteen years old, his father died, and in the next year both his mother and a brother died of the cholera. Suddenly without financial support, he was fortunate to be taken into the family of Jan Evangelista Purkyně who had accepted a professorship at the university at the University of Prague. Sachs was admitted to the university in 1851.
Sachs famously labored long hours in the laboratory for Purkyně, and then long hours for himself each day after his work in the laboratory was finished. After the lab, he could devote himself entirely to establishing how plants grow.
In 1856 Sachs graduated as doctor of philosophy, and then adopted a botanical career, establishing himself as Privatdozent for plant physiology. In 1859 he was appointed physiological assistant to the Agricultural Academy of Tharandt (now part of the Technical University of Dresden) at Julius Adolph Stöckhardt; and in 1862 he was called to be director of the Polytechnic at Chemnitz, but was almost immediately transferred to the Agricultural Academy at Poppelsdorf (now part of the University of Bonn), where he remained until 1867, when he was nominated professor of botany in the University of Freiburg.
In 1868 he accepted the chair of botany in the University of Würzburg, which he continued to occupy (in spite of calls from more prestiguous German universities) until his death.
Sachs achieved distinction as an investigator, a writer and a teacher; his name will ever be especially associated with the great development of plant physiology which marked the latter half of the 19th century, though there is scarcely a branch of botany to which he did not materially contribute. His earlier papers, scattered through the volumes of botanical journals and of the publications of learned societies (a collected edition was published in 1892-93), are of great and varied interest. Prominent among them is the series of "Keimungsgeschichten," which laid the foundation of our knowledge of microchemical methods, as also of the morphological and physiological details of germination. Then there is his resuscitation of the method of "water-culture," and the application of it to the investigation of the problems of nutrition.
Most important are his experiments, developing the concept of photosynthesis, that the starch-grains, found in leaf chloroplasts, depend on sunlight. A leaf that has been in sunlight, then bleached white and stained with iodine turns black, proving its starch content, whereas a leaf from the same plant that has been out of the sun will remain white. A demonstration of this experiment is shown in the second episode of BBC Four's "Botany: A Blooming History" presented by Timothy Walker.
Sachs's later papers were almost exclusively published in the three volumes of the Arbeiten des botanischen Instituts in Würzburg (1871–88). Among these are his investigation of the periodicity of growth in length, in connection with which he devised the self-registering auxanometer, by which he established the retarding influence of the highly refrangible rays of the spectrum on the rate of growth; his researches on heliotropism and geotropism, in which he introduced the clinostat; his work on the structure and the arrangement of cells in growing-points; the elaborate experimental evidence upon which he based his "imbibition-theory" of the transpiration-current; his exhaustive study of the assimilatory activity of the green leaf; and other papers of interest.
Sachs' first published volume was the Handbuch der Experimentalphysiologie des Pflanzen (1865; French edition, 1868), which gives an admirable account of the state of knowledge in certain departments of the subject, and includes a great deal of original information. This was followed in 1868 by the first edition of his famous Lehrbuch der Botanik, by far the best book of its kind. It is a comprehensive work, giving an able summary of the botanical science of the period, enriched with the results of many original investigations. The third edition was translated into French by Philippe Édouard Léon Van Tieghem in 1873, and into English by Alfred Bennett in 1875, and published by Oxford University Press. The fourth and last German edition was published in 1874, and also issued by Oxford in 1882.
The Lehrbuch was eventually superseded by the Vorlesungen uber Pflanzenphysiologie (1st ed., 1882; 2nd ed., 1887; Eng. ed., Oxford, 1887), a work more limited in scope, but yet covering more ground than its title would imply; though it is a remarkable book, it has not gained the general recognition accorded to the Lehrbuch. Finally, there is the Geschichte der Botanik (1875); a brilliant and learned account of the development of the various branches of botanical science from the middle of the 16th century up to 1860, of which an English edition was published in 1890 by the Oxford Press. As a teacher Sachs exerted great influence, for his vigorous personality and his ready and lucid utterance enabled him not only to instruct, but to fire his students with something of his own enthusiasm.
A full account of Sachs' life and work was given by Professor Goebel, formerly his assistant, in Flora (1897), of which an English translation appeared in Science Progress for 1898. There is also an obituary notice of him in the Proc. Roy. Soc. vol. lxii.
In 1885 he became foreign member of the Royal Netherlands Academy of Arts and Sciences.
Many pupils of Sachs like Julius Oscar Brefeld, Francis Darwin, Karl Ritter von Goebel, Georg Albrecht Klebs, Spiridon Miliarakis, Hermann Müller-Thurgau, Fritz Noll, Wilhelm Pfeffer, Karl Prantl, Christian Ernst Stahl and Hugo de Vries became later famous botanists.
The standard botanical author abbreviation Sachs is applied to species he described.
- 1859: Physiologische Untersuchungen über die Keimung der Schmikbohne (Phaseolus multiflorus)
- 1859: Ueber das abwechselnde Erbleichen und Dunkelwerden der Blätter bei wechselnder Beleuchtung
- 1862: Ueber das Vergeilen der Pflanzen
- 1863: Ueber den Einfluss des Tageslichtes auf die Neublidung unt Entfaltung verschiedener Pflanzenorgane
- 1865: Handbuch der Experimentalphysiologie der Pflanzen
- 1868: Lehrbuch der Botanik, 3rd ed. 1873, 4th ed. 1874
- 1871–1872: Die Geschichte der Botanik vom 16. Jahrhundert bis 1860 (Digital edition from 1875 by the University and State Library Düsseldorf)
- 1878: Ueber die Anordnung der Zellen in jüngsten Pflanzentheilen
- 1882: Die Vorlesungen über "Pflanzenphysiologie
- 1892: Gesammelte Abhandlungen über Pflanzenphysiologie
- 1894: Mechanomorphosen und Phylogenie
- 1896: Phylogenetische Aphorismen und über innere Gestaltungsursachen oder Automorphosen