EDITORIAL Plant Signaling & Behavior 10:9, e1079679; September 2015; © 2015 Taylor & Francis Group, LLC

Julius Sachs (1832–1897) and the Unity of Life Ulrich Kutschera1,* and Frantisek Baluska2,* 1

Institute of Biology; University of Kassel; Kassel, Germany; 2IZMB; University of Bonn; Bonn, Germany

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n 1865, the German botanist Julius Sachs published a seminal monograph entitled Experimental-Physiologie der Pflanzen (Experimental Physiology of Plants) and hence became the founder of a new scientific discipline that originated 150 y ago. Here, we outline the significance of the achievements of Sachs. In addition, we document, with reference to his Vorlesungen u€ber Pflanzen-Physiologie (Lectures on the Physiology of Plants, 1882), that Sachs was one of the first experimentalists who proposed the functional unity of all organisms alive today (humans, animals, plants and other “vegetable” organisms, such as algae, cyanophyceae, fungi, myxomycetes, and bacteria).

Keywords: experimental plant physiology, Julius Sachs, plant science *Correspondence to: Ulrich Kutschera, Email: [email protected]; Frantisek Baluska, Email: [email protected] Submitted: 05/12/2015 Accepted: 07/31/2015 http://dx.doi.org/10.1080/15592324.2015.1079679 Editorial for the Special Focus: Julius Sachs – Founder of Experimental Plant Physiology (1865)

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The historian of science George Sarton (1884–1956) once wrote that “progress has no definite and unquestionable meaning in other fields than in the fields of science,” and, in other words, that “the acquisition and systematization of positive knowledge are the only human activities which are truly cumulative and progressive (Sarton 1936).1 However, this truism does not mean that the advancements in the natural sciences (physics, chemistry, geology, biology) occur steadily at the same pace: outstanding individuals, like Isaak Newton (1642–1726), John Dalton (1766–1844), Charles Lyell (1797–1875) or Charles Darwin (1809–1882) have contributed much more than most of their contemporaries, who remain in the shadow of these geniuses. One of the lesser well-known scientists, who founded a new discipline, experimental plant physiology, was the German botanist Julius Sachs (1832–1897) (Fig. 1). Born in 1832 in Breslau (now Wroclaw, Poland), Sachs began his scientific studies Plant Signaling & Behavior

as private assistant of Jan Evangelista Purkinje (1787–1869), who was his only mentor. In 1856, he earned a Ph.D. at the University of Prague, where Sachs became Lecturer of Plant Physiology one year later. After two short periods as assistant/ teacher in Tharandt/Chemnitz, respectively, Sachs was appointed in 1861 to the Agricultural Academy (College) at Poppelsdorf/Bonn, where he wrote his seminal Handbuch der Experimental-Physiologie der Pflanzen (Experimental Physiology of Plants).2,3 In this monograph,4 the author summarized the knowledge of his time on the function of “green organisms,” such as algae, bryophytes and angiosperms (i.e., seed germination, organ development, respiration, phototropism, tissue tension, protoplasmic streaming etc.). Moreover, he introduced novel principles for controlled, quantitative experimentation4 and described numerous novel techniques for the study of physiological processes. In 1867, Sachs succeeded Anton de Bary (1831–1888) as Professor at the University of Freiburg, and, one year later, took over the chair of botany at Wuerzburg University, where he remained, and worked (up to 16 h per day), until his death in 1897. In his last book, the Vorlesungen u€ber Pflanzen-Physiologie (Lectures on the Physiology of Plants) (1882),5 Sachs discussed, in Chapter XXXIV, the topic of “Spontaneous periodic movements” in the following words: “I have repeatedly had cause to refer to certain resemblances between the phenomena of irritability in the vegetable kingdom and those of the animal body, thus touching a province of investigation which has hitherto been far too little cultivated. In the last instance, indeed, I might say animal and vegetable life must of necessity agree in all essential points, including the phenomena of e1079679-1

Figure 1. Portrait of the plant biologist Julius Sachs, drawn by his daughter Maria. The painting is integrated into one of Sachs’ numerous original illustrations (upper part of a common climbing plant, the white bryony, Bryonia dioica L.) (adapted from ref. 3).

irritability also, since it is established that the animal organism is constructed entirely and simply from the organic substances produced by plants, and ultimately it is simply from the properties of these substances that all vital movements both of plants and animals are to be explained” (Sachs 1882, p. 733). In the next sentence, Sachs (1882) pointed out that this “rule” not only applies to animals, but also to the body of humans. It should be noted that, in the 19th century, the “vegetable kingdom” also included cyanophyceae, algae, fungi, myxomycetes and bacteria. Finally, few years before his death, Sachs also introduced the concept of Energide as the smallest unit of eukaryotic forms of life, unifying plants and animals also at the cellular level.6-8 Sachs followed steps of the German naturalist Alexander von Humboldt

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(1769–1859) in his notion that plants, similar to animals, are likewise living systems endowed with sensitivity to and activity toward their external environment.9 In addition to von Humboldt, the French physiologist Claude Bernard (1813–1878) was convinced that animals and plants display the same physiological features which allow them to survive and reproduce under rather harsh environmental conditions.10 In his 2014-book Plant Behavior and Intelligence, Antony Trevawas11 refers to the Vorlesungen of Sachs,5 and summarizes evidence for an ancient, evolutionarily derived desire of human beings to be surrounded by green plants (Fig. 1). In gardens and open forests, humans feel to be in a “psychologically-satisfying environment” that is reminiscent to the open African savannah, with some trees and little

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ponds – the place where we evolved about 2 million years ago. It has long been known that Homo sapiens-individuals of all ethnicities prefer to live in natural (plant-based) environments, and try to avoid, in the long-term, to stay in “nongreen” urban settings – to become imprisoned without access to natural surroundings is clearly one of the harshest punishments for human beings. Moreover, patients that are in contact with plant-based (natural) surroundings show a more rapid recovery than those who stay in a sterile, un-natural hospital room. However, despite this “vegetatio-philia” of most humans, the phenomenon of “plant blindness” with respect to the physiology and behavior of sessile, green organisms, still prevails. With the publication of his Experimental-Physiologie der Pflanzen (1865)4 and its descendant, the Lectures (1882),5 Sachs established the analysis of plant form, function and behavior as an independent scientific discipline. As the articles published under the headline “Julius Sachs 1865 – Experimental Plant Physiology 2015” in the journal PSB show, his legacy is still alive and well today. References 1. Sarton G. The Study of the History of Science. Harvard University Press, Cambridge, Massachusetts, 1936. 2. Pringsheim EG. Julius Sachs, der Begr€under der neueren Pflanzenphysiologie. Verlag Gustav Fischer, Jena, 1932. 3. Gimmler H. (Ed.) Julius Sachs und die Pflanzenphysiologie heute. Verlag Phys Med Ges, Wuerzburg, 1984. 4. Sachs J. Handbuch der Experimental-Physiologie der Pflanzen. Verlag Wilhelm Engelmann, Leipzig, 1865. 5. Sachs J. Vorlesungen €uber Pflanzen-Physiologie. Verlag Wilhelm Engelmann, Leipzig, 1882. 6. Sachs J. Beitr€age zur Zellenlehre Energiden und Zellen. Flora 1892; 75:57-67 7. Sachs J. Weitere Betrachtungen u €ber Energiden und Zellen. Flora 1895; 81:405-34 8. Baluska F, Volkmann D, Barlow PW. Cell-cell channels and their implications for Cell Theory. In: CellCell Channels, F Baluska, D Volkmann, PW Barlow (eds), Landes Bioscience, 2006; pp 1-18. 9. von Humboldt A. Versuche u €ber die gereizte Muskel- und Nervenfaser nebst Vermuthungen u €ber den chemischen Process des Lebens in der Thier- und Pflanzenwelt. Posen, 1797 (Let Me Print, September 2012) 10. Bernard C. Lectures on the Phenomena of Life Common to Animals and Plants. Paris, 1878, Charles C. Thomas Pub Ltd (June 1974) 11. Trevawas A. Plant Behaviour and Intelligence. Oxford University Press, Oxford, 2014.

Volume 10 Issue 9

Julius Sachs (1832-1897) and the Unity of Life.

In 1865, the German botanist Julius Sachs published a seminal monograph entitled Experimental-Physiologie der Pflanzen (Experimental Physiology of Pla...
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