Esau, Katherine

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(b. Yekaterinoslav [also spelled Ekaterinoslav], Russia [later Dnepropetrovsk, Ukraine], 3 April, 1898;

d. Santa Barbara, California, 4 June 1997), plant anatomy, phloem structure and function, transmission electron microscopy, plant ultrastructure, plant viruses.

Esau was the quintessential botanist of the twentieth century, a century that echoed her own long lifespan of ninety-nine years. Best known for her textbooks on plant structure and development, Esau literally wrote the book on plant anatomy for U.S. botanists. Her textbooks Plant Anatomy (“Big Esau,” 1953, 2nd ed., 1965; 3rd ed. by Ray F. Evert, 2006) and especially Anatomy of Seed Plants(“Little Esau,” 1960, 2nd ed., 1977) directly or indirectly served to educate several generations of American plant biologists in plant anatomy with a clarity of presentation and illustration that has remained unparalleled. Botanists who never knew her personally nevertheless happily count themselves among her students.

As essential to botany as her textbooks have been, Esau’s research contributions reach far beyond that of textbook author. For more than six decades she undertook pure and applied research, studying pathological and normal tissue development. Her work, initially based on field studies in plant breeding and genetics of crop plants, led to a definitive structure-function understanding of phloem (food conducting) tissue, first at the level of light microscopy and later, in pioneering studies with transmission electron microscopy, at the ultrastructural level. Her research questions included understanding the pathways of several economically important plant viruses (long before the basic structure of viruses was clearly understood), their relationship to the infected phloem tissues, and the elusive structure of the phloem itself. Her treatise The Phloem, published in 1969 as Volume 5 of the Hand-buch der Pflanzenanatomie, reviewed studies of phloem from their inception and relied much on information from her own research efforts. This volume has been hailed as the most important of this series and essentially the bible of phloem.

By the early 1960s already the preeminent American plant anatomist, Esau moved beyond the level of light microscopy and embarked on the use of transmission electron microscopy (TEM) for the study of plant subcellular (ultrastructural) features, pioneering the use of this tool for plant cellular biology. In 1963, at an age when many would be considering retirement, she left her position at the University of California at Davis to follow her colleague and collaborator Vernon Cheadle to UC–Santa Barbara, where he became chancellor, and where she established a TEM laboratory that was later given her name. During the next twenty-two years, which she counted as the most productive of her career, she maintained a highly active research program on plant and plant-viral ultrastructure and function, securing National Science Foundation funds for TEM facilities and refining techniques for ultrastructural study of plant tissues. The TEM provided a magnificent tool for further elucidating the fine details of both normal and pathological tissues, for documenting the mode of infection and propagation of plant viruses, and for better understanding the development of phloem structure. These studies lay the groundwork for the current understanding of plant viruses and phloem structure and function.

Esau received considerable recognition throughout her career. Among her honors were a Guggenheim fellowship in 1940 for work at Harvard, a Faculty Research Lectureship at the University of California, Davis (the highest honor the faculty can give to a peer) in 1946; election to the National Academy of Sciences (the sixth woman to receive this honor) in 1957 and to the American Philosophical Society in 1964. She served as president of the Botanical Society of America in 1951 and received from this group one of the first of its Merit Awards in its Fiftieth (Golden) Anniversary year in 1956. In 1989 Esau was the first trained botanist to receive the President’s National Medal of Science from George H. W. Bush, at age ninety-one.

Family Background and Career Path . Esau was born in Russia (now Ukraine) to Johan (John) Esau and Margrethe Toews Esau, both of whom came from highly educated German Mennonite families. Her great-great grandfather Aron Esau had emigrated to the Ukraine from Prussia in 1804 along with many German Mennonites in response to Catherine the Great’s invitation to foreigners who could help to improve Russian agriculture. Mennonites as a religious group had been alternately tolerated and exiled throughout Europe, in part because of their pacifist beliefs. Many had a reputation as excellent farmers, and rural communities in various parts of Europe benefited from the establishment of Mennonite colonies. Strong community, a serious work ethic, a simple life, and an appreciation of education were values deeply ingrained in Esau’s character. She honored this background with a highly disciplined, ascetic life that ultimately contributed to her remarkable academic success.

In 1869 Esau’s father, Johan, and his brother Jacob became the first Mennonite boys in their community to go to a Russian school. Her father became a mechanical engineer and later went on to establish much of the infrastructure of the city of Yekaterinoslav, of which he later became mayor, and her uncle became a physician. In an ironic turn of fate these children of immigrant ancestry had to flee their own homes in 1917, during the Bolshevik Revolution, as Johan Esau was now considered loyal to the tsarist regime. Esau’s family went to Germany, where they had relatives. For the next two years she studied agriculture, first at the Berlin Landwirtschaftliche Hochschule and then at the Hohenheim College of Agriculture near Stuttgart, returning to Berlin to obtain the title Land-wirtschaftlehrerin and later to pass the Zusatzprufung in plant breeding. Her father’s skill in managing money enabled the family to emigrate to the United States in 1922.

The Esau family relocated in Reedley, California, near Fresno, because there was a strong Mennonite community there. Within a few years Esau began working as a plant breeder in fields first near Oxnard and later Salinas, studying the curly top viral disease in sugar beets. Her interests in selecting for disease-resistant strains of the plants culminated in her first research paper in 1930 in Hilgardia, the University of California’s journal of agriculture. At that time basic viral structure, let alone the mode of viral transmission, was poorly known. Esau began to study the tissues of pathological and normal plants comparatively, and as she did this, began to realize the need for understanding normal development.

A shift from plant geneticist to plant anatomist came about as Esau entered graduate school in 1928. Her work was centered at the relatively young agricultural school at UC–Davis; however, because Davis did not have a graduate degree program, her graduate work was administrated through Berkeley, where she also took several courses. At the time of her studies, other researchers at Davis began a program on standardizing beet varieties. Because they did not want their study sites to be infected with curly top and because the leafhoppers who were vectors for its transmission did not grow well in Davis, Esau’s work became less field-oriented and more anatomical. In her dissertation research she did a comprehensive comparison of the cells and tissues of infected and normal plants, in particular the phloem tissues. Upon completion of her dissertation in 1932, she was hired as a lecturer and researcher at the University of California at Davis, where she worked until 1963. Her work continued at Santa Barbara thereafter well into her nineties, and she lived in Santa Barbara until her death in 1997.

Legacy . Esau’s most important contributions depended on her exceptionally careful and clear comparative study of the cells and tissues of healthy and infected plants. Whereas other plant anatomists took a static view of structures, her studies were dynamic, following the development and differentiation of tissues. Her descriptions are a clear, concise, cell-by-cell account of the changes that occur with development or with infection. As a writer her considerable facility with language (including fluency in German, Russian, English, French, Spanish, and Portuguese) was essential to the work; she was well acquainted with the German and Russian literature and was able to incorporate this information into her English-language texts. She consulted regularly with her colleague, the writer Celeste Turner Wright, to improve her writing.

Esau’s talents in writing, illustrating, and communicating also made her an excellent teacher and public speaker. She had a droll sense of humor that delighted her students and audiences. She was known to start her lectures with the words “Once upon a time,” which led students to refer to the lectures as “Esau’s fables.” She invented a continuing story, “The Saga of Vladimir the Virus, or the Account of the Tragic Fate of Norman the Nucleus,” to illustrate the progress of viral infection of a cell’s nucleus with a series of electron micrographs.

Esau was a very successful collaborator, working with Robert Gill on phloem ultrastructure, James Cronshaw on the characterization of P-protein (formerly called “slime” in phloem), and Lynn Hoefert on plant virus research. She also collaborated with Vernon Cheadle on the comparative anatomy of phloem and its evolutionary significance. Esau directed fifteen PhD students, mostly at Davis, and numerous postdoctoral associates. Her students included Hugh Wilcox (mycorrhizae) and Peter Kaufman (gravitropic response; gibberellins). Perhaps her best-known student is Ray F. Evert, who continued her studies of phloem ultrastructure, wrote plant biology textbooks, and in 2006 revised Esau’s Plant Anatomy. Jennifer Thorsch became Esau’s last graduate student when Esau was eighty-one years old and remained close to her in her final years.

Esau’s legacy is rooted in the fundamental descriptive science of plant anatomy precisely because it is a highly practical and necessary field of endeavor. She trained not only pure but applied scientists who needed to understand the economically important plants that she studied with such rigor. With exceptional skill, dedication, and good humor she became a fundamental figure in understanding and teaching plant anatomy, and she remains foremost in the minds of those who care about plant structure and function.

In 1993 she established the Katherine Esau Fellowship Program at the University of California at Davis for junior faculty members, visiting scholars, and postdoctoral researchers. In recognition of her legacy, the Katherine Esau Award of Botanical Society of America is given annually at the society’s meeting.


Katherine Esau’s papers are deposited in the Department of Special Collections, Donald C. Davidson Library, University of California, Santa Barbara. Details are available at Prepared slides, photographs, and other materials from the research of Esau and her colleague and collaborator Vernon Cheadle are housed in the Vernon I. Cheadle and Katherine Esau Structural Botanical Collections, University of California, Santa Barbara; information is available from


“Studies of the Breeding of Sugar Beets for Resistance to Curly Top.” Hilgardia 4 (1930): 417–441. Esau’s first paper, based on her early work in plant breeding for resistant crops, drawn on her work at the Spreckle Seed Company near Salinas, California.

“Origin and Development of Primary Vascular Tissues in Seed Plants.” Botanical Review 9 (1943): 125–206.

Plant Anatomy. New York: Wiley, 1953; 2nd ed., 1965. A complete and detailed text on the development and structure of the vegetative structures (leaves, stems, roots, wood, and bark) of vascular plants. The long-anticipated revision of this text has been published as Evert, Ray F., Esau’s Plant Anatomy: Meristems, Cells, and Tissues of the Plant Body: Their Structure, Function, and Development, 3rd ed., Hoboken, NJ: Wiley, 2006. This edition includes many of the original figures from Esau’s original texts and research and is an updated discussion of developments in the field.

“Primary Vascular Differentiation in Plants.” Biological Review 29 (1954): 46–86.

With Vernon I. Cheadle. “Secondary Phloem of Calycanthaceae.” University of California Press, Publications in Botany, Berkeley29 (1958): 397–510. A paper surveying variations in secondary phloem tissue and its value for comparative taxonomic purposes.

Anatomy of Seed Plants. New York: Wiley, 1960; 2nd ed., 1977. A more streamlined version of the principles of plant anatomy that also includes chapters on plant reproductive structures (flowers, fruits, seeds), this text has been used extensively in plant anatomy courses and in the early 2000s forms the basis for how many botanists teach the discipline.

Plants, Viruses, and Insects. Cambridge, MA: Harvard University Press, 1961.

Vascular Differentiation in Plants. New York: Holt, Rinehart and Winston, 1965.

“Anatomy of Plant Virus Infections.” Annual Review of Phytopathology 5 (1967): 45–76.

With James Cronshaw. “Relation of Tobacco Mosaic Virus to the Host Cells.” Journal of Cell Biology 33 (June 1967): 665–678.

Viruses in Plant Hosts: Form, Distribution, and Pathologic Effects. Madison: University of Wisconsin Press, 1968.

The Phloem: Handbuch der Pflanzenanatomie. Band V, Teil 2, Histologie. Berlin-Stuttgart: Gebrüder Borntraeger, 1969. Part of a series of books that treat detailed topics in plant anatomy, this volume details the structure, function, and variation known in the phloem tissue in the late 1960s, including some of Esau’s first electron micrographs.

With Robert H. Gill. “Aggregation of Endoplasmic Reticulum and Its Relation to the Nucleus in a Differentiating Sieve Element.” Journal of Ultrastructure Research 34 (1971): 144–158.

With Lynn L. Hoefert. “Ultrastructure of Sugar Beet Leaves Infected with Beet Western Yellows Virus.” Journal of Ultrastructure Research 40 (1972): 556–571.

With Jennifer Thorsch. “Sieve Plate Pores and Plasmodesmata, the Communication Channels of the Symplast: Ultrastructural Aspects and Developmental Relations.” American Journal of Botany 72 (October 1985): 1641–1653. (Special paper.)

With Robert H. Gill. “Distribution of Vacuoles and Some Other Organelles in Dividing Cells.” Botanical Gazette 152 (1991): 397–407. Esau’s last paper, at age ninety-one.


Evert, Ray F. “Commentary: The Contributions of Katherine Esau.” International Journal of Plant Sciences 153 (September 1992): v-ix. This commentary is part of a special Festscrift dedicated to Katherine Esau which includes contributed papers from the Katherine Esau International Symposium, held at UC Davis March 28–31, 1992.

———. “Katherine Esau: Address Given by President-Elect Ray F. Evert.” Plant Science Bulletin 3 (October 1985). Available from One of Esau’s most prominent graduate students, Evert focused his address as president-elect of the Botanical Society of America on Esau’s life and scientific accomplishments.

O’Hearn, Elizabeth Moot. “Profiles of Pioneer Women Scientists: Katherine Esau.” Botanical Review (July 1996): 209–271. New York Botanical Garden. This source includes detailed information on Esau’s research studies, honors, and graduate students; reminiscences from her academic peer and friend Celeste Turner Wright, and an addendum containing a biography of her father, Johan Esau.

Ruddat, Manfred, and Edward D. Garber. “Editorial.” International Journal of Plant Sciences 153 (September 1992): iii-iv. This editorial introduces a special Festscrift dedicated to Katherine Esau which includes contributed papers from the Katherine Esau International Symposium, held at UC Davis March 28–31, 1992.

Stebbins, George Ledyard. “Katherine Esau (3 April 1898–4 June 1997).” Proceedings of the American Philosophical Society143 (December 1999): 665–672. Available from This summary provides insight from one of Esau’s most prominent botanical contemporaries and colleagues on the broad significance of her work.

Thorsch, Jennifer, and Ray F. Evert. “Katherine Esau.” American Journal of Botany 84 (November 1997): 1621–1623.

———. “Katherine Esau, 1898–1997.” Annual Review of Phytopathology 36 (September 1998): 27–40. These two final references are coauthored by Jennifer Thorsch, Esau’s last graduate student, who cared for her in her later years, and Evert, who carried on much of Esau’s work on phloem. They provide an outline to Esau’s professional activities as well as some personal reminiscences.

Kathleen E. Pigg