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Women Pioneers in Plant Biology
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Recognizing that plant physiology was an area of study that very few women actively pursued until the 1980s, the Women on Plant Biology Committee would like to acknowledge those women who were pioneers in studying plants and how they work. Their research areas are very diverse: genetics, biochemistry, structure, as well as physiology. Their education, training, and career paths are also diverse. However, as witnessed by the biographies written by former students, fellow researchers, admirers, or good friends, each of these women has contributed to the broad field of plant physiology, and we are grateful to them.

If you would like to write a biography about someone who you believe should be honored in our Women in Plant Biology Hall of Fame, please contact us.

Hildegarde von Bingen


Hildegarde von Bingen

Listen to a musical excerpt from Cum processit factura, excerpt from Healing Chants (requires RealPlayer)

Hildegarde von Bingen Although plant biology now has a considerable number of practitioners who are women, this was not always the case. Even three-quarters into the twentieth century, there were few women in research or academic positions who pursued the study of plant biology. The women featured in this website were pioneers. By following their heart and their interest in studying plants and plant processes, they paved the way for many women who followed them. The Women in Plant Biology Committee is pleased to highlight the careers of these women so that their contributions to science and to humanity will not be forgotten.

Our earliest pioneer is Hildegard of Bingen. Hildegard was born in 1098 in Boeckelheim to Hildebert, a nobleman, and his wife Mechthild of Bermersheim. Hildegard was their tenth child and as was the tradition of the time, Hildegard was dedicated to the church. At eight years of age, she was sent to study with Jutta von Spanheim, the sister of Count Meginhard and the Abbess at a Benedictine convent that had been founded in 675. Jutta taught a number of young girls in addition to Hildegard, who learned Latin and music, and read the works of Galen, Dioscorides and other ancient scholars. When Jutta died, Hildegard, by then a Benedictine nun, replaced her as the Abbess of the cloister; she was 38 years old at the time. At the age of 50, she founded a new convent in Rupertsburg near Bingen, and later in her life, she established another one across the Rhine, on the east bank, in Eibingen. She corresponded with emperors, kings, bishops, cardinals, and popes, and was well known in Germany and abroad.

Hildegard was a mystic, subject to visions, which some have suggested resulted from migraine headaches, and also an illness, which sometimes left her bedridden. In spite of these difficulties, Hildegard was a prolific writer of books and music; she was also a painter. In addition, she was a stalwart supporter of the medieval Church. Parts of her first book, Scivias (Know the Way of the Lord), were read by Pope Eugene III at the Synod of Trier in 1147. This established her reputation, and numerous pilgrims came to the convent to consult with Hildegard. In addition to hymns, paintings, and books on dogma, Hildegard wrote two books, Physica (Natural History) and Causae et Cures (Causes and Cures), dealing with plants and medicine. The original Physica manuscript, which was probably written in 1150, is lost. What remains are parts of the manuscript dating from the 13th to the 15th centuries, and a printed version dating from 1533. Hildegard died in 1179 at the age of 81, and although almost a millennium has gone by, her works, especially her music, are still known today.

Hildegard's contribution to plant biology was as an herbalist. In her time, plants were primarily written about in terms of their impact on human health. The herbalists usually copied the works of Dioscorides and Theophrastus, producing handwritten manuscripts that were lavishly illustrated. Hildegard took another approach. Her books are not merely copies of previous texts; rather they are Hildegard's own reflections on plants and their medical uses, based in part on the Bible and knowledge of the past, but also on local wisdom. Many monasteries and convents in the Medieval Europe were the repositories of medical knowledge for much of the local population. Some of Hildegard's recommendations, such as using Psyllium for "fevers in [the] stomach", or hemp, which-"if one is weak in the head, and has a vacant brain, eats hemp, it easily afflicts his brain. It does not harm one who has a healthy head and full brain"-have validity today. Although her approach to medicine recognized that plants could help remedy certain ills, she was also very sanguine about the efficacy of some of the suggested cures. She wrote in Causae et Cures: "These remedies come from God and will either heal people or they must die, or God does not wish them to be healed".

In Isley's book, One Hundred and One Botanists, one of the references used in preparation of this biography, Hildegard of Bingen is one of only four women who are profiled. There must have been many others since Hildegard's time and now, no doubt numerous unsung heroines, either working behind the scenes or neglected by history. Our goal in this website is to bring women pioneers in plant biology out of the shadows and into the light.

Ann M. Hirsch, University of California-Los Angeles

Literature Cited
Isley, D. 1994. One Hundred and One Botanists. Iowa State University Press. Ames, IA.
Strehlow, W. and Hertzka, G. 1988. Hildegard of Bingen's Medicine. Bear & Company, Santa Fe, NM.
Throop, P. 1998. Hildegard von Bingen's Physica. The Complete English Translation of Her Classic Work on Health and Healing. Healing Arts Press, Rochester, VT.


Harriet Creighton (1909-2004) was the third woman elected to the presidency (1956) and the first woman secretary (1950-54) of the Botanical Society of America (BSA). Creighton's many contributions to the BSA and to botanical education are often overshadowed by her most cited work, the first demonstration of cytological and genetical crossing-over in Zea mays. The investigation was part of Creighton's dissertation research project at Cornell University (1929-1934), under the guidance of her collaborator, Dr. Barbara McClintock, who had suggested the problem. Their study provided additional confirmation of the chromosome theory of inheritance for which Thomas Hunt Morgan would win a Nobel Prize in 1933.

Creighton's publications and early contributions to maize genetics may be found in issues of Proceedings of the National Academy of Sciences (PNAS), Maize Genetics Cooperation News Letter, Records of the Genetics Society of America, and citations to her works appear in many books and journals, whose authors also acknowledge her for sharing data. Her major contributions to our field, however, are her behind-the-scenes participation on many national science education committees for the BSA, the American Institute of Biological Sciences (AIBS), and the National Science Foundation's National Research Council (NSF/NRC). Much of her involvement on these committees has been described in the pages of the Plant Science Bulletin (PSB), of which she was a founding member and editor by 1958. She wrote articles encouraging innovation in teaching, and in her retiring presidential address, she encouraged her fellow botanists to be as proud as she was of their botanical roots, and challenged them with the call "Botanists of the World, Unite! and Get Going."

Early Achievements, 1929-1940

The Cornell Years: Creighton was born in Delavan, Illinois on June 29, 1909. At age 20 she graduated from Wellesley College (A.B. 1929), and accepted an assistantship (1929-1932) in General Botany in the Department of Botany, College of Agriculture, at Cornell University. There, Dr. Barbara McClintock suggested that she pursue a Doctorate in Cytology with Professor Lester W. Sharp. McClintock also suggested Creighton's minor subject areas, Plant Physiology and Genetics. In 1929, Creighton learned many new plant cytological techniques from McClintock, who years later would win the Nobel Prize for her discovery of transposable elements in corn.

By 1931, Creighton and McClintock used a semisterile corn stock with a prominent knob at the tip of the short arm of chromosome 9, and having a piece of chromosome 8 attached (a translocation) for their study of a correlation of "genetical and cytological crossing over," published in the August 1931, PNAS. At the 6th International Congress of Genetics, held at Cornell in 1932, Creighton and McClintock collaboratively presented evidence for 4-strand crossing over in corn. Creighton continued to contribute unpublished data to the Maize Genetics Cooperation News Letter, and published new findings on deficiencies on chromosome 9 of corn.

As a graduate student, Creighton was elected to the Women's Scientific Fraternity, Sigma Delta Epsilon (Graduate Women in Science) in 1930 (established at Cornell in 1921) and she later became an officer of the National organization. In 1931, she was elected to the Cornell Chapter of the honorary scientific society, Sigma Xi, and to Phi Kappa Phi, in 1932. Creighton completed her doctorate in 1933 and remained in the Botany Department at Cornell as an Instructor of cytology and microtechnique (1932-1934), until accepting a job at Connecticut College for Women (CCW) in 1934.

Connecticut College for women, 1934-1940: Creighton was an Instructor in Botany at CCW (1934-1938) and was promoted to Assistant Professor in 1938. In 1935, with McClintock, she published a corroboration of their investigations of cytological crossing over. Creighton worked collaboratively with G.S. Avery, P.R. Burkholder, and others at Connecticut College, on a translation and revision of Peter Boysen-Jensen's (1883-1959) Growth Hormones in Plants, which was expanded to include 188 new contributions to the literature and 40 additional illustrations. With Avery, Burkholder, and others at Connecticut College, she also conducted a series of plant physiology experiments that were mainly published in the American Journal of Botany (AJB) between 1936 and 1941.

Contributions 1940-1974

In 1940, Creighton was appointed Associate Professor of Botany at Wellesley College, and was elected a Fellow of the AAAS. In addition to teaching, she continued to conduct research on corn. Soon after the U.S. entered World War II, Creighton was granted a leave of absence for war service (1943-May 1946) and rose to the final rank of Lieutenant Commander in the WAVES.

Upon returning to Wellesley, she was appointed Chair of her Department. She enthusiastically supported Wellesley's Arboretum, Botanic Gardens and The Margaret C. Ferguson Greenhouses as "premier educational sites" and was committed to maintaining them as such. In 1946, she initiated Garden Day, where local garden clubs were invited to Wellesley to view the greenhouse and gardens. This eventually led to the founding of the Wellesley College Friends of Horticulture (WCFH) in 1982, whose members raised funds for the renovation of the Ferguson Greenhouses, completed ten years later. The Harriet B. Creighton Room at the Visitor Center of the Margaret C. Ferguson Greenhouses was dedicated to honor her years of service to the Botany Department and her ongoing support for the College's Botanic Gardens.

Creighton served as Secretary of the BSA Teaching Section (1948-1951), was a member of the AAAS Council (1949-1951), and was elected Secretary of the BSA in 1950. She was promoted to Professor of Botany in 1952 and that year she was a Fulbright Lecturer at the University of Western Australia, Perth, and at Adelaide University. Seven years later, she again was a Fulbright Lecturer at the National University of Cuzco, Peru.

In 1955, Creighton was named the Ruby F.H. Farwell Professor of Botany at Wellesley. In that year, she was also elected Vice-president of the BSA, served on the PSB editorial board (through 1959) and participated (through 1958) in an NSF Panel for the selection of Predoctoral Fellows. She also served as a Member-at Large for the 14th -16th (1955-1957) Symposium of the Society for Developmental Biology.

Professor Creighton's commitment to Botanical Education: As a member of the Botanical Society's Education Committee, Creighton supported their proposal to the National Science Foundation (NSF) for a Summer Institute for Botany teachers from small colleges to be held at Cornell in 1956. Creighton served on NSF Panels for Summer Institutes for College and High School Teachers of Biology through 1959. She was one of the outstanding lecturers who participated in the NSF-supported Summer Institute for College Botany Teachers, sponsored by the BSA, in 1959. Concurrently, she was a member of the NSF Committee on Teaching Biology (1956-1957), and was invited to join the AIBS Committee on Education and Professional Recruitment's Steering Committee (1956-1966) for the Secondary School Film Series in which she played a "teacher" in several individual films. While editor of PSB, Creighton (1958) encouraged writers and publishers of Botany and Biology text books to "experiment with texts that are really a third arm of a course, the first two being the teacher and the organisms studied in the field and laboratory."

Creighton was secretary (1960-1963) of Section G (Botanical Sciences) of the AAAS, and concurrently chaired the BSA's Committee on Education for two years (1960-1962). The Committee studied the Role of Botany in America, and she helped to formulate their recommendations concerning High School Biology Courses, and Introductory Courses in Biology. As part of her responsibilities for this committee, Creighton was a botanical consultant (1961-1969) to A. J. Nystrom and Co. (Chicago), who produced teaching charts and models of plant structure, which she had designed.

Research interests and further responsibilities: Creighton pursued research on the genetics of Petunia flowers, which she presented independently, and with students, at the annual meetings of the Genetics Society of America (GSA) in the 1940s. Later, she became interested in the horticultural aspects of Begonia. Those studies were presented at the BSA, and published in The Begonian during the 1960 and 1970s. She spent a sabbatical year in the Botany Department at the University of California, Berkeley (1966) and at the Cell Research Institute of the University of Texas in Austin (1967).

In the early 1960s, she was President of the Wellesley Chapter of the Society of Sigma Xi. She traveled to India as a consultant for NSF (1968, 1969) and also accepted committee assignments from the GSA. Creighton was an editorial board member (1969-1975) of the Journal of College Science Teaching, representative to the Executive Committee from the Historical Section of the BSA (1973) and in addition, refereed book manuscripts, journal articles, and published many book reviews. She taught a class on Basic Botany and Horticulture for the Massachusetts Horticultural Society, and gave a National Science Teachers Association workshop for high school teachers on the use of plants for experiments in their classes.

The Retirement Years 1974-2004, and beyond

Honors and Recognition: Creighton kept busy after her 1974 retirement as Ruby F.H. Farwell Professor Emerita. She was consulted on all aspects of Wellesley College life and wrote the chapter on "The Grounds" for the centennial volume Wellesley College 1875-1975, A Century of Women. The Massachusetts Horticultural Society honored her with the Large Gold Medal of their society in 1985, for her botanical expertise and "horticultural concern in the community." In 1994, The Wellesley College Alumnae Association recognized her with the Syrina Stackpole Award for "dedicated service and exceptional commitment to Wellesley College."

Posthumous honors: Creighton died at age 94, on January 9, 2004. That year, the Wellesley College Botanical Greenhouse Fund, established by Creighton in 1955 with an initial modest gift, was renamed the Harriet Creighton Greenhouse Fund for continued support of the Margaret Clay Ferguson Greenhouses.

Creighton lived a long, happy, and successful life. Her legacy of contributions to Botany in the 20th century has persisted and sustained the broad field of Plant Biology.

-- by Lee B. Kass, Visiting Professor, Cornell University, excerpted from:
Kass, L. B. 2005. Harriet Creighton: Proud Botanist. Plant Science Bulletin 51(4): 118-125.

Harriet Creighton outside the Margaret C. Ferguson Greenhouses, Wellesley College, 1994 (Photograph by Lee Kass).

Johanna Döbereiner (1924 - 2000)

Johanna Döbereiner was a remarkable woman, a true pioneer in the study of plant-microbe interactions.  Her early life was not easy.  Born November 28, 1924 in the former Czechoslovakia, her family was forced to immigrate to Germany at the end of the World War II.  After completing her graduate work at the University of Munich, she moved to Brazil in 1951 and became a Brazilian citizen in 1956.  She joined the Research Department of the Brazilian Ministry of Agriculture (currently known as Embrapa) in the 1950’s where her career lasted for almost 50 years.  Here, she started her research on what is now known as associative nitrogen fixation.  When she began, little attention was given to the possibility that nitrogen-fixing bacteria were associated with non-legume crops, particularly the cereal grasses, and furthermore, that these bacteria could promote plant growth by providing fixed nitrogen.  In her early work, Johanna found a number of bacteria in Brazilian soils, including Azotobacter (later named Azorhizophilus) paspali and Beijerinckia fluminense, in soils surrounding cereal grasses; B. fluminense was also found in the rhizoplane of sugarcane.  She also studied a number of Brazilian species of Azospirillum, the only bacterial genus other than the rhizobia used as inoculants for crops.

Two critical events in the 1970’s enabled Johanna to advance her research further.  One was the petrleum crisis of the early 1970’s, which caused the price of chemical fertilizer to increase significantly, and the other was the development of the acetylene reduction assay (ARA), a relatively easy detection system for determining low levels of nitrogenase, i.e. biological nitrogen fixation (BNF), activity.  Many Brazilian pasture grasses tested positive for nitrogenase activity using ARA and a semi-solid medium developed by Johanna and her students, strongly suggesting the presence of an associated nitrogen-fixing bacterial species.  In the 1980’s, Johanna and her colleagues found a number of nitrogen-fixing bacteria that colonized the inner tissues of plants (endophytes, a term coined by Johanna).  Herbaspirillum seropedicae was isolated from maize, sorghum, and rice, whereas Gluconoacetobacteria diazotrophicus was isolated from sugarcane.  Indeed, various sugarcane varieties were found to obtain 30 to 50% of their nitrogen from BNF via endophytic bacteria although no single genus has been identified as the source of fixed nitrogen.  Nevertheless, associative nitrogen fixation was firmly established as a means of providing fixed nitrogen to plants.  Currently, 5 million hectares of Brazilian farmland is planted in sugarcane, and more than half of the cane is processed into 13 billion liters per year of bioethanol, which fuels 10-12 million cars.

However, Johanna did not envision "microbe hunting” as her ultimate goal.  She and her colleagues noted different responses of maize and other cereal grain cultivars to the endophytes and thus advocated breeding programs to capitalize on the genetic diversity inherent in the plants.  She insisted on breeding high-yielding soybeans on nitrogen-deficient soil so they that were completely dependent on BNF.  The net result was that such a strategy reduced Brazil’s dependence on chemical fertilizer, thus saving billions of dollars annually.  It also led to Brazil becoming the second largest grower of soybean in the world after the U.S. and made the nation a dominant force in the agricultural marketplace.

For her contributions to Brazilian agriculture, Johanna was the recipient of many awards during her lifetime, including membership in the Brazilian Academy of Science and the Vatican Pontifical Academy of Sciences (there are only 75 members throughout the world).  She was a founding member of the Third World Academy of Sciences and also a member of the New York Academy of Sciences.  She was honored with the title Doctor "Honoris Causa” from the University of Florida and the Federal Rural University of Rio de Janeiro.  She was the recipient of more than 12 national and international prizes and also received many other international honors, such as the Bernardo A. Houssay Science Prize from the Organization of American States.  One of her students noted in the obituary he wrote that Johanna was the most cited Brazilian female scientist and the seventh most cited Brazilian by the international community.  Her scientific output was large not only in research papers and presentations at meetings, but also in the number of students and trainees that she mentored.  She was the subject of numerous magazine and newspaper articles in Brazil, especially after the news leaked out that she had been nominated for the Nobel Prize in Chemistry in 1997.  Although she did not win this prize, she already had won the respect and admiration of many, especially her students and colleagues in the nitrogen fixation field.

Johanna Döbereiner passed away on October 5, 2000.

Baldani, J.I., and Bandani, V.L.D.  2005.  History on the biological nitrogen fixation research in gramineous plants:  special emphasis on the Brazilian experience.  Ann. Brazil. Acad. Sci.  77: 549-579.
Baldani, J.I., Bandani, V.L.D., and Reis, V.M.   2002. Johanna Döbereiner:  fifty years educated to the biological nitrogen fixation research area.  In:  Nitrogen Fixation:  Global Perspectives.  Eds.  T. Finan, M. O’Brian, D. Layzell, K. Vessey, and W. Newton.  CABI Publishing, N.Y., N.Y.  Pp.  3-4.
Boddey, R.M., Urquiaga, S., Alves, B.J.R. and Reis, V.  2003.  Endophytic nitrogen fixation in sugarcane:  present knowledge and future applications.  Plant Soil.  252: 139-149.
Franco, A.A., and Boddey, R.M.  1997.  Dr. Johanna Döbereiner:  a brief biography.  Soil Biol. Biochem.  29:  ix-xi.

Photograph by Robert M. Boddey

Katherine Esau, Ph.D., N.A.S.

Katherine Esau

"Dedicated to the brilliant scholar Professor Emeritus Katherine Esau. An illuminating teacher, classic textbook author, and historical monographer; A critical researcher and lucid explicator on plant viruses, developmental and pathologic plant anatomy, and on ultrastructure of phloem, for whom these facilities were designed when she came to this campus from UC-Davis in 1963."

This dedication, written by her close colleague and friend, Vernon I. Cheadle, appears on the plaque designating the research building that served as the laboratory and electron microscope facility of Dr. Katherine Esau on the University of California-Santa Barbara campus.

Katherine was born on April 3, 1898, in the city of Yekaterinoslav, now called Dnepropetrovsk, in the Ukraine. She lived there until the end of 1918, when she and her family fled to Germany during the Bolshevik Revolution. When the Esau family fled Russia, Katherine had just completed her first year of study at the Golitsin Women's Agricultural College in Moscow. Upon arriving in Germany, Katherine enrolled in the Agricultural College of Berlin. She spent three years at the college and developed a close acquaintance with Professor Erwin Baur, a geneticist who became famous for his studies in plant breeding.

In 1922, the Esaus left Germany for the United States, where they settled in Reedly, California, a strong Mennonite community. In 1923, Katherine took a job with the Sloan Seed Company in Oxnard, California. One year later, she was hired at the Spreckels Sugar Company in Salinas, California, to develop a sugarbeet resistant to curly-top disease, a virus that was a major problem to growers in that state. In 1928, Katherine left Spreckels to begin her graduate studies at the University of California-Berkeley. This marked the beginning of her exceptional and productive 64-year career in plant anatomy.

Katherine graduated from Berkeley in 1932 and was employed at UC-Davis as an instructor and junior botanist. Throughout her career, she studied phloem, the food conducting tissue in plants, both in relation to the effects of the phloem-limited viruses upon plant structure and development and to the unique structure of the sieve tubes, food conducting cells. Katherine had an exceptional ability for attacking basic problems, and she set new standards of excellence for the investigation of anatomical problems in the plant sciences.

During her tenure at UC-Davis, Katherine received many honors and distinctions, including a Certificate of Merit on the Golden Jubilee Anniversary of the Botanical Society of America in 1956; election to the National Academy of Sciences in 1957; and an honorary degree from Mills College, Oakland, in 1962. She also served as President of the Botanical Society of America in 1951.

In 1963, Katherine moved to Santa Barbara to continue her collaboration with Dr. Vernon I. Cheadle, who had been appointed Chancellor of that UC campus. They had been research colleagues at UC-Davis for 10 years studying the comparative structure of the food conducting tissue in higher plants. She considered her years in Santa Barbara to be her most productive and fulfilling. She had been introduced to electron microscopy just before leaving Davis, and she was interested in applying this new tool to her anatomical research. An electron microscope, the first on the Santa Barbara campus, was purchased and installed soon after her arrival. Although Katherine retired in 1965, she remained actively engaged in research for 24 more years.

In 1989, Katherine was awarded the President's National Medal of Science by George H. Bush. The citation accompanying the medal reads: "In recognition of her distinguished service to the American community of plant biologists, and for the excellence of her pioneering research, both basic and applied, on plant structure and development, which has spanned more that six decades; for her superlative performance as an educator, in the classroom and through her books; for the encouragement and inspiration she has given to a legion of young, aspiring plant biologists; and for providing a special role model for women in science."

Katherine was especially well known for her beautifully written and comprehensive textbooks. Her first book, Plant Anatomy, was published in 1953, and it became a classic almost immediately. The book was and still is fondly called the "bible" for structural botanists. Her developmental approach and thorough presentation of the structure and development of a wide variety of economically important plants resulted in a book that revitalized plant anatomy throughout the world. In 1961, Anatomy of Seed Plants, was published for less comprehensive courses. These books provided a standardized and unified terminology for plant anatomy. Between 1965 and 1977, she revised her Plant Anatomy book and Anatomy of Seed Plants and wrote three additional books: Vascular Differentiation in Plants; Viruses in Plant Hosts: Form, Distribution, and Pathologic Effects; and The Phloem. The Phloem covers the structure and development of the phloem, beginning with the earliest records of this tissue. It is one of her greatest contributions.

Katherine was a superb teacher, serving as major professor for 15 doctoral students. She gave freely of her time and was always available to provide advice, encouragement, and praise. I was fortunate to be her last graduate student, joining her laboratory in 1979, when she was 81 years old. Our relationship as mentor and student transformed to colleague and friend, and ultimately my role became one of providing care and assistance during the last several years of her life.

Jennifer Thorsch, University of California Santa Barbara

Enid MacRobbie, ScD, FRS, FRSE

Enid MacRobbie Throughout her career, Enid MacRobbie has been at the forefront of studies of ion transport in plants, addressing fundamental questions in plant nutrition and cell signalling. She pioneered the use of radiotracers to measure ion fluxes, identified active and passive transport processes and their regulation in giant algae, and unravelled the transport events involved in stomatal movement in higher plants. She has trained a succession of outstanding Ph.D. students, who have gone on to become influential scientists in their own right, and has won worldwide recognition and honors for her research. There is no doubt that her career has helped change conditions for women scientists, to the benefit of those who have followed.

Enid was born in Edinburgh, Scotland in 1931 and attended high school and university in that city. She studied physics for her B.Sc. degree and was awarded a 1st class honors in 1953. She stayed at the University of Edinburgh for her Ph.D. becoming the first graduate student in Jack Dainty's new biophysics research group. The group was part of the Department of Physics, but, characteristically in those post-war years, was accommodated in a converted chicken house behind the Department of Genetics. In her Ph.D. project, Enid made the first use of radioisotopes to measure ion fluxes in plants. Her initial work was with the seaweeds Rhodymenia palmata and Ulva lactuca, but she subsequently moved to the conceptually simpler system of the giant internode cells of the alga Nitellopsis obtusa. Her thesis work established the theoretical framework for, and practical application of, isotope efflux analysis-a technique that had been developed in animal cells, but which was made more complicated in plants because of the presence of the large central vacuole. The resulting papers were pioneering and immediately established Enid's reputation in her chosen field.

At the end of her Ph.D. research in 1957, Enid moved to a postdoctoral position with Professor H. H. Ussing at the Institute of Biological Isotope Research in Copenhagen where she studied ion transport in frog skin. After one year there, she secured a Research Fellowship at Girton College in Cambridge and moved back to the United Kingdom. Enid's initial hope had been to work with Nobel Laureate Alan Hodgkin in the Department of Physiology but, given her interests, he suggested that it might be better if she joined George Briggs, Professor of Botany, who was interested in the ionic relations of plant cells. Thus began her association with the Botany School (now Department of Plant Sciences) in the University of Cambridge where she has been an inspirational colleague for more than 40 years. Briggs gave Enid freedom to follow her instincts, and she began using isotopes to measure fluxes of K+, Na+ and Cl- in the giant alga Nitella translucens. Her main aim was to establish which fluxes at the plasma membrane and tonoplast were active and which were passive, and how they were regulated, information that was essential to establish the molecular mechanisms of ion movement in plants. The work was outstandingly successful. It secured her international reputation and helped establish a more quantitative and biophysical approach to studies of plant transport systems.

Professor Briggs retired in 1960 and teaching quantitative plant physiology was taken over by Enid, Michael Pitman, and Martin Canny. When, in 1962, Michael Pitman left Cambridge for the University of Adelaide, Enid was recruited to the Demonstratorship (Cambridge's equivalent of a non-tenured Assistant Professorship) he vacated. Her research was given a major boost when, in 1964, she, Jack Dainty (by then the inaugural Professor of Biophysics at the newly-opened University of East Anglia), and Charles Whittingham (at Imperial College, London) were awarded a substantial 5-year grant by the Nuffield Foundation. This allowed Enid to build a group quickly and to establish strong links with the Dainty group in Norwich. The latter brought the additional benefit of contacts with a number of talented Australian biophysicists, including Alex Hope, Alan Walker and Geoff Findlay, who became life-long scientific friends and collaborators. The Nuffield grant was doubly useful because it came with no strings attached, and Enid could spend with complete flexibility, a sharp contrast with the limitations placed on modern grants in these days of accountability! This period also saw the start of Enid's role as an inspirational Ph.D. supervisor when F. Andrew Smith joined her in 1962 as her first Ph.D. student. A year later, John Raven and John Cram were recruited, and the group quickly grew to ten, including Roger Spanswick, who was a postdoctoral associate.

From 1962 to the mid-1970s, the group was concerned mainly with characterizing ion fluxes at the plasma membrane and tonoplast of giant algae, but in 1978, Enid made a major change in research direction when she decided to begin studying the mechanism of stomatal guard cell movement, the fundamental process by which plants regulate the uptake of gases and the loss of water. The switch to stomates was driven by the realization that the nature of the fluxes underlying changes in ion content during opening and closing were largely unknown. Enid began studying this problem using her established methods, but adapting them to the more challenging guard cell system. She received her first grant for this work in the early 1980s and it has remained the mainstay of her research since then. As with her work on giant algae, Enid has made an important contribution to our understanding of the control of stomatal closure and her research has provided important quantitative flux information that complements studies done by other means, such as patch clamping.

Enid's laboratory has been the incubator for the fledgling career of many now-distinguished plant physiologists. These include F. Andrew Smith, John Raven, John Cram, Roger Spanswick, Mel Tyree, Richard Williamson, Dale Sanders, Roger Leigh, Carol Shennan, Mike Blatt, Mark Tester, Mary Beilby, and Gerhardt Thiel, to name just a few. Enid's input to the work of her colleagues is always constructive. She is able to identify and focus on the key issues, and through this, draw the best out of others. Her positive outlook on the work of her colleagues remains the abiding memory of many of her former students and postdocs. As one former postdoc put it: "Some of my fondest memories of my time in Cambridge are of sitting with Enid talking through data or ideas and coming away knowing that I've been 'stretched' and have enjoyed the experience."

An unusual feature of Enid's approach is that she has actively encouraged the majority of the people who have worked with her to publish papers without her name on them. Thus only about 25% of the papers published by her colleagues during their time in her lab have included her as a co-author. Therefore, any literature search using her name as key words will substantially underestimate the full extent of the output of her laboratory. This has been a remarkably selfless approach to science that has given added impetus to the careers of those whom she has mentored. It is unlikely that, in these days of citation analyses, present or future scientists will feel willing or able to make such a magnanimous gesture. As a result of her unselfish approach, it can be guaranteed that the papers with Enid's name on them indicate that she made a real and important practical contribution to the work. Throughout her career, she has always conducted her own experiments and all her free time is spent at the bench. Even now, following her official retirement in 1999, and at the start of her eighth decade, she remains active and can daily be seen performing flux measurements, reviewing papers, or offering advice to younger colleagues who regularly seek her counsel.

Enid's influence extends well beyond her own research laboratory. In her role as a teacher, she has influenced generations of Cambridge undergraduates to consider a career in research. Together with the late Tom ap Rees, she revolutionized the content of botanical courses in Cambridge in the 1960s and 1970s by introducing more cell biology and biochemistry, and emphasising quantitative approaches and analytical thinking. She was particularly effective in the small-group tutorial teaching that is a special part of teaching in Cambridge, and it is not uncommon to meet former undergraduates for whom Enid's teaching has been a life-long inspiration. Girton College, where she has been a Fellow since 1958, was the first women's college in Cambridge and has an outstanding record of promoting equal opportunities for women in higher education. In her role as a teacher at the College, Enid influenced many women undergraduates to pursue science as a career and many of them have gone on to gain international recognition.

Enid's career has resulted in many honors and measures of esteem, although often these came scandalously late considering the influence she has had on her field, possibly because she was a woman in a male-dominated environment and because of her policy of letting students and postdocs publish without her. She was appointed to a permanent Lectureship in 1966, was promoted to a Readership in 1972, and to a Personal Professorship in 1987, the first woman scientist in Cambridge to be awarded a Personal Chair. A year later, she was awarded a Doctor of Science (Sc.D.) by the University. She was elected a Fellow of the Royal Society of London (the highest honor in U.K science) in 1991, is a Fellow of the Royal Society of Edinburgh (elected 1998), and a Foreign Member of the National Academy of Sciences of the USA (since 1999). She is also a Corresponding Member of the American Society of Plant Biologists. Her 40 years of service to Girton College were recognized by her election to a Life Fellowship in 1999. In her spare time, which even in retirement is not abundant, Enid amuses herself with gardening, walking, and trout fishing. The latter is mainly done when she escapes to her holiday house in Kilchoan on the Ardnamurchan Peninsula, the most westerly point on mainland Scotland.

Throughout her career, Enid MacRobbie has sought to make biologists think quantitatively. Often she has had an uphill struggle because most consider themselves mathematically inept and unable to use equations. Enid's aim has been to show them that they can, and that their scientific understanding is enhanced as a result. Her own work more than adequately demonstrates how a quantitative approach can enlighten, and her outstanding achievements as a scientist, teacher, and unselfish individual will have influence on plant physiology for many years. Her legacy will be both an outstanding research record and a cohort of talented individuals who have gone on to make their own mark on plant biology.

Roger A. Leigh, Department of Plant Sciences, University of Cambridge

Lynn MargulisLynn Margulis
Distinguished University Professor
University of Massachusetts Amherst

Lynn Margulis is Distinguished University Professor in the Department of Geosciences at the University of Massachusetts, Amherst. Her publications, spanning a wide range of scientific topics, include original contributions to cell biology and microbial evolution. She is best known for her theory of symbiogenesis, which challenges a central tenet of neodarwinism. She argues that inherited variation, significant in evolution, does not come mainly from random mutations. Rather, new tissues, organs, and even new species evolve primarily through the long-lasting intimacy of strangers. The fusion of genomes in symbioses followed by natural selection, she suggests, leads to increasingly complex levels of individuality. Dr. Margulis is also acknowledged for her contribution to James E. Lovelock's Gaia concept. Gaia theory posits that, on the Earth, surface interactions among living beings, sediment, air, and water have created a vast self-regulating system.

Professor Margulis helps develop hands-on science teaching activities at levels from middle to graduate school, including Introduction to the Carbon Cycle: What happens to trash and garbage?; Living Sands, Using Forams to Map Time and Space and Peas and Particles: Estimating Large Numbers to Understand Natural Selection. She has made many short videos of live organisms for advanced students and researchers; the most recents ones are Eukaryosis: Origin of Nucleated Cells and Forbidden Fertilization. She is the author of many articles and books. The most recent include Symbiotic Planet: A new look at evolution (1998) and Acquiring Genomes: A theory of the origins of species (2002), co-written with Dorion Sagan. Indeed, over the past decade and a half, Professor Margulis has co-written a number of books with Sagan, among them What is Sex? (1997); What is Life? (1995); Mystery Dance: On the evolution of human sexuality (1991); Microcosmos: Four billion years of evolution from our microbial ancestors (1986); and Origins of Sex: Three billion years of genetic recombination (1986). Her work with K. V. Schwartz provides a consistent formal classification of all life on Earth and has led to the third edition of Five Kingdoms: An illustrated guide to the phyla of life on Earth (1998). Their evolutionary classification scheme was generated from the scientific results of numerous colleagues. The logical basis for it is summarized in her single-authored book Symbiosis in Cell Evolution: Microbial communities in the Archean and Proterozoic eons (second edition, 1993). The bacterial origins of both chloroplasts and mitochondria are established. At present, with colleagues and graduate students, she explores the possible origin of cilia from spirochetes. Experiments and observations involve studies of free-living mud spirochetes, sequence comparisons of eukaryotic motility proteins with those of spirochetes and other prokaryotes, and cytological studies with termite archaeprotists (amitochondriates under anoxic conditions such as the devescovinids and calonymphids).

Margulis teaches Environmental Evolution, a course on the effects of life on the evolution of the Earth's surface, primarily to seniors and graduate students, although science teachers tend to take the course in the summer. This course itself evolves. She often has taught it with her PhD students. MIT Press has published a second edition of the text for the course, which has been taught every semester since it was begun at Boston University in 1972.

Dr. Margulis received her AB degree in liberal arts from the University of Chicago, her Master's degree in Zoology and Genetics at the University of Wisconsin-Madison and her PhD in genetics at the University of California , Berkeley. She was elected to the National Academy of Sciences in 1983 and received the Presidential Medal of Science from President William J. Clinton in 1999. She was a recipient of an Alexander von Humboldt prize from Germany in 2002. The Library of Congress announced in 1998 that it will permanently archive her papers. Prior to her move to the Botany Department at the University of Massachusetts, she was a faculty member at Boston University for 22 years.

Barbara McClintock (1902-1992)

Barbara McClintock (1902-1992), one of the foremost women scientists in 20th century America, is most noted for her pioneering research on transposable elements in maize. For this work, she was awarded the Nobel Prize in Physiology or Medicine in 1983. She was the third woman to receive an unshared Nobel Prize in the sciences.

Born in Hartford, Connecticut, on June 16, 1902, Barbara McClintock was raised in Brooklyn, New York. After graduating from Erasmus Hall high school, she entered Cornell University at age 17, and in 1923 earned a B.S. in agriculture, concentrating in plant breeding and botany. She received both her masters (1925) and doctoral degrees (1927) from Cornell's College of Agriculture. She majored in cytology with Lester Sharp in the Department of Botany, and minored in genetics and zoology with A.C. Fraser and H.C. Reed in the Departments of Plant Breeding and Zoology, respectively. As a graduate student, McClintock was a research and teaching assistant in the Department of Botany. During these years, Sharp referred both botany and plant breeding graduate students and post-doctoral researchers to her. Most notable were George Beadle (Ph.D. 1930), who learned cytology from McClintock and went on to head the biology division at Caltech and to win a Nobel Prize, and L. J. Stadler (NRC Fellow 1926) later elected to the National Academy of Sciences.

McClintock's career as one of the most prominent geneticists of the 20th century was launched while she was at Cornell. Upon receiving her doctorate, McClintock was made an Instructor. At that time, this appointment was the first step leading to tenure at colleges and universities like Cornell. Jobs in academia were scarce during the Depression, and jobs for women were limited. While employed at Cornell, Instructor McClintock continued to mentor and collaborate with graduate students. She befriended graduate student Marcus Rhoades (Ph.D. 1932), who also rose to preeminence in genetics and was McClintock's lifetime supporter. From 1927 to 1931, she taught undergraduate and graduate courses in Cornell's Department of Botany.

In early 1929, McClintock published her Ph.D. dissertation in Genetics, then the foremost journal in the field. Within two years, she had published six other articles in major journals, all of which made important contributions to the newly emerging field of plant cytogenetics, and furthered the world's knowledge about the location of genes on chromosomes. She collaborated with students on the most notable of these investigations.

Instructor McClintock gave graduate students Henry Hill and Harriet Creighton two important projects for their thesis research and co-authored these pioneering contributions with them. The first was a method to connect chromosomes with linkage groups in corn (McClintock & Hill 1931) and the second was the cytological proof for crossing over (McClintock 1931, Creighton & McClintock 1931). Creighton and McClintock's significant study gave further confirmation to T. H. Morgan's chromosome theory of inheritance, for which he won a Nobel Prize in 1933. These collaborative projects were based on important work that McClintock had pioneered: identification of corn's ten chromosomes at mitosis (and later at meiotic pachytene stage), confirmation of Belling's translocation hypothesis, and the sequence of the genes in Chromosome 9. Creighton (Ph.D. 1933) became head of Botany at Wellesley College and President of the Botanical Society of America in 1956.

From 1931 through 1934, sponsored by two National Research Council Fellowships, and a prestigious Guggenheim Fellowship, McClintock traveled to a series of important research institutions across the U.S., Germany, and back to Cornell, where she worked in the Department of Plant Breeding as an assistant to R. A. Emerson, head of the department. There, she conducted research, funded by the Rockefeller Foundation, which would provide insights to an understanding of variegation and would eventually lead to her Nobel award winning investigations.

In 1936, McClintock accepted an appointment as Assistant Professor of Botany at the University of Missouri to join L. J. Stadler's genetics research group. Upon learning that the research unit might be eliminated, and preferring research over teaching, McClintock requested a leave of absence from Missouri in 1941 to seek employment elsewhere. In 1943, she accepted a position as a permanent staff member of the Carnegie Institution of Washington's Department of Genetics at Cold Spring Harbor. It was there she discovered mobile genetic elements in corn for which she was awarded the Nobel Prize in Medicine or Physiology in 1983. She remained at Cold Spring Harbor for the duration of her career, accepting only short term appointments at national and international institutions elsewhere.

McClintock achieved considerable recognition within her lifetime. In 1944, prior to her most celebrated work, she was elected to the National Academy of Sciences, the third woman so honored. McClintock also became the first woman elected Vice President (1939) and President (1945) of the Genetics Society of America. By 1947, she received the Achievement Award from the American Association of University Women.

But it is for McClintock's work with maize at Cold Spring Harbor beginning in the mid 1940s, her meticulous observations of the dynamism of the genome, her communications of her theory of genetic transposition-the idea that genes could change their position on a chromosome-that cemented her reputation as a geneticist, which was widely acknowledged in later years. In 1957, the Botanical Society of America recognized her achievements with their esteemed Merit Award, and Cornell appointed her one of their first A.D. White Professor's-at-Large in 1965 (renewed in 1971).

McClintock also won a number of prizes during her later career. A few months before she formally retired in 1967, she received the Kimber Genetics Award from the National Academy of Sciences. In that year, the Carnegie Institution of Washington appointed her a Distinguished Service Member, one of their highest honors, which made it possible to continue working at Cold Spring Harbor Laboratory. During the 1970s she received the National Medal of Science (1970), the Lewis S. Rosensteil Award (1978), and the Louis and Bert Freedman Foundation Award (1978). A few years before receiving the Nobel Prize, she was honored with many awards; more notable were the Thomas Hunt Morgan Medal, the Wolf Foundation Prize in Medicine, a shared Albert Lasker Basic Medical Research Award, and the first Prize Fellow Laureate of the MacArthur Foundation.

McClintock's life as a scientist was not always easy. Full appreciation of the implications of her work, which challenged generally held beliefs that the chromosome had a stable structure, was not possible until molecular biologists found similar phenomena in bacteria and other organisms. As one of the early women scientist in this country, McClintock was recognized early on for her pioneering achievements; gaining a star in American Men of Science by 1944. Yet, as an aspiring young geneticist, she experienced rejection because of her gender. Determined to succeed in her chosen field, and respected and helped by devoted colleagues, McClintock eventually found a position at an institution that gave her the freedom to pursue her love of science and which, she said, "fit her personality rather well."

--by Lee B. Kass, Visiting Professor, Cornell University

COE, ED & LEE B. KASS. 2005. Proof of physical exchange of genes on the chromosomes. Proceedings of the National Academy of Science 102 (No. 19, May): 6641-6656.
COMFORT, NATHANIEL C. The Tangled Field: Barbara McClintock's Search for the Patterns of Genetic Control. Harvard University Press, 2001 [see critical book reviews by NINA FEDOROFF. 2002. The well mangled McClintock myth. Trends in Genetics 18 (7): 378-379, and LEE B. KASS. 2002. The Tangled Field, by N. Comfort. Isis. 93 (4): 729-730].
FEDOROFF, NINA & DAVID BOTSTEIN, editors. 1993. The Dynamic Genome: Barbara McClintock's Ideas in the Century of Genetics. Cold Spring Harbor Laboratory.
KASS, LEE B. 2000. McClintock, Barbara, American botanical geneticist, 1902-1992. Pp. 66-69, in Plant Sciences, edited by R. Robinson, Macmillan Science Library, USA
KASS, LEE B. 2003. Records and recollections: A new look at Barbara McClintock, Nobel Prize-Winning geneticist. Genetics 164 (August): 1251-1260.
KASS, LEE B. 2005a. Missouri compromise: tenure or freedom. New evidence clarifies why Barbara McClintock left Academe. Maize Genetics Cooperation Newsletter 79: 52-71
KASS, LEE B. 2005b. Harriet Creighton: Proud Botanist. Plant Science Bulletin 51(4): 118-125.
KASS, LEE B. and CHRISTOPHE BONNEUIL. 2004. Mapping and seeing: Barbara McClintock and the linking of genetics and cytology in maize genetics, 1928-1935. Chap. 5, pp. 91-118, in Hans-Jörg Rheinberger and Jean-Paul Gaudilliere (eds.), Classical Genetic Research and its Legacy: The Mapping Cultures of 20th Century Genetics. London: Routledge.
KASS, LEE B. CHRIS BONNEUIL, & ED COE. 2005. Cornfests, cornfabs and cooperation: The origins and beginnings of the Maize Genetics Cooperation News Letter. Genetics 169 (April): 1787-1797.
KELLER, EVELYN FOX.1983 (reprinted 1993). A Feeling for the Organism: The Life and Work of Barbara McClintock. W.H. Freeman & Co..

Photo above: Cornell University 1929: (from right to left) Instructor Barbara McClintock with Professor R.A. Emerson and his graduate students Marcus Rhoades and George Beadle (kneeling), and Post-doctorial National Research Council Fellow Charles Burhnam (used with permission of W. B. Provine).

Margaret E. McCully, Ph.D, F.R.S.C.

Dr. Margaret McCully Margaret E. McCully was born in St. Marys, Ontario, Canada. After receiving her bachelor’s degree in agriculture at the University of Toronto in 1956, she taught chemistry and biology at Shelburne High School in Ontario before returning two years later to the University of Toronto to complete her master’s degree in plant ecology. For her degree, Margaret studied the morphology and ecology of the common Mare’s tail, Hippuris vulgaris. After moving to England where she taught for two years in an English school, Margaret returned to North America in 1966 to study at Harvard, where she completed her Ph.D. in cell biology on the histology of the brown alga Fucus. She came back to Canada to take a faculty position at Carleton University in Ottawa where she spent the vast majority of her academic career.

Margaret’s diverse training has given her a broad outlook. She has touched upon many areas of science, from phycology to microbiology, from anatomy to physiology. Along with T.P. O’Brien, Margaret co-wrote a reference book for microscopists entitled "The Study of Plant Structure—Principles and Selected Methods”; this book is used throughout the world and contains a wealth of information of plant histochemistry and cytology. Margaret is best known, however, as an expert in root biology and her papers on this topic illustrate the broad base of her studies; she is as much at ease writing about techniques to study roots as about their anatomy and physiology. Root structure, root development, root behavior in the field, biology of the rhizosphere, water status of the plant, ion uptake, lateral root development, techniques for microscopy (light, fluorescence, electron), x-ray microanalysis—all of these are grist for Margaret’s mill. She has published more than a hundred papers in internationally refereed journals, and in the process, she has changed our views about many of these fields. One of the most significant findings, done in collaboration with Martin Canny, her husband, is that water does not enter the field-grown corn roots just near their apices but rather along their entire length. A description of this research can be found in the 1999 Annual Review of Plant Physiology and Plant Molecular Biology, entitled "Roots in Soil: Unearthing the Complexities of Roots and their Rhizospheres.”

Margaret is very well known internationally. She has held visiting fellowships, lectureships, or professorships at the University of Leeds and Oxford University in the United Kingdom; the University of California, Davis in the United States; and Monash University, the University of Melbourne, LaTrobe University, and the University of Western Australia in Australia. She was elected a Fellow of the Royal Society of Canada in 1987, and in 1993 received a degree of D.Sc. (honoris causa) conferred by St. Mary’s University in Halifax, Nova-Scotia, Canada. Margaret has received a number of other honors, including two Carleton University Academic Staff Association Scholarly Achievement Awards and a major research achievement prize from Carleton University. In 1996, she was awarded the Lawson Medal Award from the Canadian Botanical Association, and in 1994, she was invited to give the Hamm Lecture at the University of Minnesota in Minneapolis. In 1999, she and her work were recognized at the XVI International Botanical Congress in St. Louis, Missouri. A symposium was organized to honor her outstanding contributions to root biology and to plant science.

In addition to her science, Margaret McCully has been a tremendous role model for numerous students, postdoctoral scholars, and research associates. Margaret has been and still is a very demanding scientist, asking as much from her students as from herself; she has always looked for high standards and honesty. However, she has been very generous with her time and her scientific expertise, and also with her knowledge of literature, music and art. In spite of her success, Margaret continues to be genuinely interested in talking with students, undergraduate or graduate alike. She encourages her students to attend conferences, to present their work, and to talk with other participants. Very early on, she taught those of us who worked with her to "network,” to communicate not only with our peers, but also with her friends and colleagues, highly regarded scientists. Margaret encouraged her students to keep open minds and eyes to the outside world, advising them to focus broadly and not only on the tiny portion of roots they studied. Although her studies concentrated on plant organs, she never lost the sense of the organism. This is why in her lab, even though sometimes students worked on roots growing in Petri plates, they still thought of what they learned as being applied to real roots, growing in real soil. She taught students that model systems were good but only as a step to understand the bigger picture.

Margaret has been an extraordinary teacher because she is a wonderful human being. She surely put a mark on all the persons who passed through her laboratory, including the author of this biography. In Margaret’s lab, we learned on old pieces of equipment before being allowed to use the new microscope or new microtome. This was not because Margaret was worried about the state of the equipment, but rather it ensured that we understood the mechanisms of the machine before we went on to work with the more sophisticated equipment. We would be able to go anywhere in the world, and work with any piece of equipment--old or new, because we understood how it functioned. Also, because of her respect for the old literature, she taught us to read it and to use it in our research. Anatomists and microscopists of the last centuries had already observed so much!

Although Margaret retired from Carleton in 1999 and subsequently moved to Australia, she continues to do research and work with new groups of students, thus conveying her enthusiasm and her love for science.

Frédérique C. Guinel, Wilfrid Laurier University.

Arlette Nougarède

Arlette Nougarède Arlette Nougarède was an active French cytologist in the field of plant morphogenesis during the last half of the twentieth century. Her name will remain associated with the elucidation of the cytophysiological organization of the angiosperm shoot apical meristem during both vegetative and reproductive development.

She was born on May 7, 1930, at Narbonne in the south of France, and moved to Paris in 1948 following the completion of her secondary studies. After brilliantly passing the basic degrees at the Faculty of Sciences of Paris, she became a C.N.R.S. associate researcher and prepared a doctorate at the Ecole Normale Supérieure. This was the beginning of a fruitful and exemplary career. She obtained her doctorate degree in 1958 and became a lecturer at the Faculty of Sciences of Paris in 1959, and finally a professor at the Pierre and Marie Curie University in 1961, where she created her own Laboratory of Experimental Cytology and Plant Morphogenesis. Arlette extended the focus of her research group to several domains of plant development including lateral rhizogenesis, bud dormancy, gravitropism, and root and shoot meristem regeneration in tissue culture, using a range of methods that allowed not only structural and ultrastructural approaches, but also a comprehensive analysis of the phenomenon under study. Many times over Arlette developed new methods for combining physiological and dynamic information with descriptive cytological data. For example, she was the first to use histoautoradiography and DNA microspectrophotometry to study plant material in France. This approach enabled her to obtain precise information on the parameters of cell cycle activity in apical meristems at various developmental stages, including the total duration of the cell cycle, the duration of each phase, and the position of specific cells in the cycle. Her pioneering work in this area is confirmed today by molecular genetic studies of the cell cycle. Her findings opened the way to modern approaches of plant developmental biology.

Confronted by serious health problems at different times of her life, Arlette proved to be exceptionally courageous and never stopped urging work along, even when hospitalized and close to being blind. During her productive scientific career, Arlette wrote 146 original and review papers. She participated actively in the major congresses on plant morphogenesis, which led to several collaborations with American and European colleagues. Among the 18 doctoral students she supervised, six are now professors in various universities and nine are associate professors.

Arlette was also an excellent teacher, not only on the topic of plant morphogenesis, but also on basic cell biology and general botany. In 1969, she wrote a comprehensive textbook of cytology, which was a major reference book at that time. Her lectures were always very thorough, and she was a mentor for many students who decided later to become teachers, scientists, or both. She was as demanding of herself as she was of others. When we, her students, were younger, we felt sometimes rather intimidated by Arlette, but her professional rigor was always compensated for by her readiness to lend support and a helping hand to all.

When she retired in 1991, a colloquium was organized by her former students in her honor under the aegis of the French Society of Botany. Throughout her career, Arlette received a number of honors and distinctions from the French Academy of Sciences of which she is now a corresponding member. From the French government she received the titles Chevalier de la Légion d'honneur, and Officier des Palmes académiques. She is also a member of the Botanical Society of America and of the Society of Biology.

Arlette has recently written a review article (Nougaréde, 2001) synthesizing the views of cytologists and molecular biologists on the concepts developed around the shoot apical meristem. This paper shows once again the open-mindedness, vision, intelligence, and capacity to integrate new ideas that characterize great scientists. There is no doubt that she would have loved to participate in the new developments in her favorite areas of research using the genetic tools that are available today.

As an Emeritus Professor, she remains in close contact with her former lab, of which the author of this biography is now the director. Moreover, as one of her students, it is with a feeling of sincere admiration and affection that I think of the life and work of Arlette, who was a most inspiring teacher.

Dominique Chriqui, University Pierre and Marie Curie, Paris

Some significant papers from Arlette Nougarède

Experimental cytology of the shoot apical cells during vegetative growth and flowering. Intern. Rev. Cytol. (1967) 21, 203-351.

Méristèmes. Encyclopaedia Universalis (1985) vol. 11, 1119-1133

Chrysanthemum segetum L. In: Handbook of flowering, (1989) vol. VI, Halevy A. H. ed., CRC Press, Boca Raton, U. S. A., pp. 196-227.

Le méristème caulinaire des Angiospermes : nouveaux outils, nouvelles interprétations. Acta Bot. Gallica (2001) 148 (1), 3-77.

Ann Oaks, B.A., M.A., Ph.D., F.R.S.C.

Dr. Ann Oaks Ann Oaks was born and raised on the frontiers of Canada, and spent her career at the frontiers of plant research. Her early upbringing in austere, but caring conditions instilled in her a strong independent will, and a keen sense of survival, as well as a lasting interest in, and compassion for nature.

Her higher education was at the University of Toronto in honors biology, where she developed an interest in plants, with the encouragement of Norm Good. She became excited by courses in physiology and biochemistry during her final years as an undergraduate, but maintained her interest in nature by working in the north during the summer months. After a year in Churchill, Manitoba, looking at cold hardiness in Chironomids, she studied the genetics and physiology of Chl-deficient mutants in barley for her master's degree at the University of Saskatchewan with Michael Shaw and Tom Arnason. Following a brief spell in Roy Waygood's lab and time at the College of Education in Toronto, she returned to Shaw's lab in Saskatoon to complete her Ph.D. on host--parasite relationships of wheat rust. There, her interest in plant biochemistry was solidified when she took a course from Arthur Neish. Then, in the late 1950s, as an Alexander von Humboldt scholar in Freising, she worked with Otto Kandler on the path of C in photosynthesis, before moving on to Harry Beever's lab in Purdue where she was initiated into the two interests that influenced the rest of her career: maize seedlings and nitrogen metabolism. She was appointed an assistant professor at McMaster University in 1965 and retired from there as a professor 24 years later. She then transferred her research to the University of Guelph as an adjunct professor for ten years.

Ann's research career has been extensive and highly successful with many publications and seminal reviews; she has received the Gold Medal Award from the Canadian Society of Plant Physiologists, and has been inducted into the Royal Society of Canada. Major contributions have been made to our understanding of the hydrolysis of protein reserves in the endosperm of germinated maize, but arguably her more recognized research has been to elucidate the pivotal role of nitrate reductase (NR) in the nitrogen status of maize seedlings. The hydrolysis of maize endosperm reserves to support seedling growth was shown in her lab to require the activity of unique sets of proteases. These act in a two-step process; initially there is cleavage of the insoluble zeins by a specific endopeptidase and the soluble products of this are then sensitive to hydrolysis by less specialized endo- and exo-peptidases. The reduced N released from the maize endosperm then has a profound effect on ability of the seedling to take up and assimilate nitrate-N. Ann and her coworkers have established the importance of the balance between amide-N and carbohydrate supply in the induction of NR and on the N-economy of the growing seedling. This understanding of the complexities of nitrogen/nitrate metabolism at the physiological and biochemical level has provided an essential prelude to the modern molecular era in which gene activity and interactions are being elucidated. Ann developed and cherished working relationships with researchers from India, Japan, Europe and N. America. She, and her students and collaborators, laid some of the foundations upon which modern technologies are being successfully applied.

Following retirement, her interests turned more strongly to the environment, providing often strident opinions to groups questioning the wisdom of utilizing water resources for commercial gain, the flagrant use of pesticides and herbicides, and especially what she felt was the under-tested introduction of genetically-modified organisms. She was a generous supporter of environmental groups, arts groups and charities; she financed an annual lecture in the College of Biological Sciences at the University of Guelph, as well as creating a munificent endowment to support graduate students through the Canadian Society of Plant Physiologists Ann Oaks Scholarship Fund.

Ann passed away, after a long and frustrating illness on Jan. 13th, 2006 at the age of 76. She recognized, espoused and imbued in her undergraduate and graduate students and colleagues the values of mentoring, of constantly challenging and questioning, and of personal discussions and contact. As a teacher, researcher, and innovator, she has made a difference.

J. Derek Bewley, University of Guelph

Beatrix Potter

Beatrix Potter (Helen) Beatrix Potter, beloved English children's author and illustrator of The Tale of Peter Rabbit and Benjamin Bunny, was also a woman pioneer in botany. Although she was born to privilege in 1866, Victorian society did not encourage women to be successful or independent. Beatrix was lonely and shy as a child, and many times her only companions were her pets, wild animals she and her brother smuggled into their rooms. Probably because of her isolated childhood, self-reliance came naturally to her. From an early age, she produced excellent drawings. Her subjects were mostly the animals, insects, and plants that she collected, all drawn with sensitivity and skill.

As a young woman Beatrix Potter developed an interest in classifying, dissecting, and drawing fungi. Through this work and her research at the British Museum, she became convinced that lichens were a symbiotic association between fungi and algae. Although we now view her research and conclusions to be an excellent example of pioneering work in the field, her work was not accepted at the time. For example, in 1897, she prepared a research paper on the symbiosis of lichens entitled "On the Germination of the Spores of Agaricineae" for the Linnean Society. However, as a woman in Victorian England, she faced resistance on all fronts. First, because women were unwelcome at meetings, she was not able to read her paper before the Linnean Society membership. Although her uncle, Sir Henry Roscoe, a distinguished chemist, read Potter's paper at the meeting, her novel ideas about the symbiosis were rejected. Finally, her future research opportunities were compromised because she was now unwelcome to continue her work at the British Museum. Although Beatrix remained a keen observer of nature for rest of her life as reflected in her Peter Rabbit illustrations, the encounter with the Linnean Society essentially ended her career as a practicing scientist.

Beatrix's career as children's author and illustrator began with an illustrated letter to the children of her ex-governess. It was the basis of The Tale of Peter Rabbit. After much success with her initial publication, Beatrix immersed herself in her new venture, writing and illustrating many wonderful tales. Because each new book was enthusiastically received, Beatrix wrote and illustrated 21 more children's picture books. Eventually, she earned quite a lot of money, which gave her financial independence. With the royalties from her books, she purchased a small farm in the Lake District, called Hilltop Farm, where she found a new focus for her energies and talents: looking after her farm, caring for her animals, and supervising her home. Hilltop farm was a very important part of Beatrix's world. The farm and the environs brought her close to nature and inspired her later books. However, it was a private world that only very few of her friends and family every glimpsed or understood.

Beatrix and her husband, William Heelis, a local solicitor, became important figures in the village of Sawrey, and they always gave back to the community that had given them so much. For example, they purchased many of the historic farms of the region to preserve them. Even in later years when health problems began to sap her energies, Beatrix continued to be an ardent naturalist, and science always remained important to her. For example, she selectively bred prize-winning Herdwick sheep.

Beatrix died quietly in the winter of 1943, leaving behind a legacy of timeless literature that continues to amaze and entertain children of all ages. However, sadly because of the times in which she lived, she never had the opportunity to develop her original interest in scientific research. One wonders what would have happened in another time.

William Eisinger, Ph.D., Department of Biology, Santa Clara University
Judith Eisinger, M.S.L.S., San Jose Public Library

References and Suggested Readings

Buchan, E. 1987. Beatrix Potter: The Story of the Creator of Peter Rabbit.
Sapp, J. 1994. Symbiosis: Evolution by Association. New York, Oxford Press.

Ruth L. Satter, Ph.D.

Dr. Ruth Satter Ruth L. Satter was a distinguished plant physiologist who worked on the mechanism of leaf movement. Her career as a scientist was quite unusual, very successful, and she enjoyed it thoroughly. Other aspects of her life were also very interesting and heart-warming, and thus it is fitting to remember her as a role model for women in science.

Ruth was born in 1923 in New York City and grew up in Lawrence, Long Island. She graduated from Barnard College in 1944 with a bachelor’s degree in mathematics and physics. Between 1944 and 1947 she worked at Bell Laboratories and at Maxson Co. For the next 17 years she stayed home to raise her four children. In 1964, when her youngest child was 2 years old, she started her study of plant physiology as a graduate student at the University of Connecticut at Storrs, in part because she loved gardening and wanted to understand plants better. At that time, it was quite unusual for a 41-year-old woman with four children to undertake a serious study of science. Her Ph.D. thesis was on control of flowering by red/far-red light in Sinningia species (Gloxinia), and her Ph.D. advisor Donald Wetherell believes she got the idea from her observation of the plants growing in her window at home.

In 1968, she moved to Yale University as a postdoctoral fellow and began studying the mechanism by which leaf movements in some legumes are controlled both by light and by the circadian clock. At Yale, she published a series of elegant papers that clearly showed that the basis of leaf movement was due to changes in K+ and Cl- content in the cortical cells of the pulvinus, and that both red and blue light phase-shift the rhythmic leaf movements. In 1980, she returned to the University of Connecticut as a professor-in residence in the Biological Sciences Group. Although not a tenure-track position, she did not complain, but instead concentrated on understanding the mechanism of rhythmic changes in ion contents in the motor cells of the pulvinus. She found that a light-sensitive H+ pump generated the driving force for K+ and Cl- fluxes into these cells. To quantify the ionic interactions precisely, she and postdoctoral fellow Holly Gorton developed methods to isolate protoplasts from the motor cells. It was very difficult to establish a reliable protocol to isolate healthy protoplasts from the tough tissues of the Samanea pulvinus, but they were successful. The protoplasts were then used, by means of the newly developed patch clamp technique, to identify the ion channels responsible for the osmotic and turgor pressure changes. Her collaborator on this project was Nava Moran, who continued researching the system to identify the mechanism of rhythmic and light-controlled regulation of ion fluxes.

At this time, in the mid-1980s, the biological community was becoming increasingly interested in signal transduction—how cells sense and transduce environmental and internal signals to produce responses. Many interesting examples of signaling pathways had been described in animal systems, and Ruth wanted to test whether leaves used one of these signaling pathways to sense and transduce light signals. She collaborated with Richard Crain, a lipid biochemist, and together they showed that the phosphatidylinositol cycle is the basic light signal transduction mechanism in the leaf motor cells. Thus, the motor cells became one of the very first plant systems shown to have the phosphatidylinositol cycle for signal transduction. In the lab, she treated her students as equals and expected them to generate ideas as good as hers. She took them to as many scientific meetings as possible, gave them plenty of time to think and read, and provided journal clubs and seminars for stimulation. She was delighted to recruit good students from foreign countries because she wanted to help young people in need. She invited her students to her home frequently and shared her culture with the foreign students. She also wanted to learn about other cultures and was open about the different ways people live.

All through her career, Ruth was happily married and was an enthusiastic mother and grandmother. When she accepted new students in the lab she took great care of them; it was as though she was expanding her family. She loved to help people develop their talents and establish a happy life, which for her, was very important, even more so than her own research. To young women, she was an excellent example of how a woman could combine career and family life, and she encouraged them to do so. Nava Moran, a senior lecturer at the Department of Agricultural Botany, Hebrew University School of Agriculture, one of the young women influenced by Ruth, had this to say: "Ruth was the first and so far the only woman that became my role model both professionally and as a person. She knew a lot about things I didn’t know, but was genuinely interested in new subjects and aspects of old subjects, was eager to learn new techniques and new approaches. I saw this when she was my student in the patch-clamp course in Woods Hole. … What I really appreciated a lot about her was her devotion to her family—she could share the time between science and family—and also the freedom of decision she gave her daughter Jane to go to El Salvador as a doctor. She was so proud of her then! ” Ruth, her husband Bob and their children were very conscious of the need to serve in ways that would improve society and the world. Her daughter Jane went to El Salvador during their civil war to help as a physician. Ruth must have been terribly worried about her daughter’s security, but she did not try to dissuade her and instead was proud that Jane was serving the human community. At various times Ruth served as a member of the Governing Board, Executive Committee, and Editorial Board of the American Institute of Biological Sciences. She was the Northeastern Region chairperson of ASPP, councilor for the American Society for Photobiology, Editorial Board member of Plant Physiology, and served as a peer reviewer and on postdoctoral fellowship panels for the National Science Foundation. She was particularly concerned about children’s and women’s issues and actively participated in American Women in Science.

Ruth was diagnosed with leukemia in 1980 and her research was often interrupted due to her medical problems. However, she came back again and again to the lab with a big smile. Her love of science was a great inspiration for everyone in the lab. Despite her enthusiasm about life and science, her health deteriorated gradually, and by 1989 she had to have blood transfusions every week. In the late summer of 1989, she decided not to fight any longer. She was 66, felt good about her whole life, and gracefully accepted death. Many in the field of plant physiology still miss her insight as a scientist and most of all, her friendship.

Youngsook Lee, Pohang Institute of Science and Technology, Korea

Helen Stafford, Ph.D.

Helen Stafford Helen Stafford was born in Philadelphia, Pennsylvania, on October 9, 1922, and attended Friends schools through high school. Her parents had both attended college, and Helen entered Wellesley College on a scholarship, where she earned her B.A. degree in Botany in 1944. She then spent one academic year (1945-46) at Cornell University as a research assistant to M. Knudsen and working with orchid cultures. Helen received a two-year assistantship with Richard Goodwin and transferred to the Connecticut College for Women in 1946, where she earned her M.A. degree in 1949. Her thesis research on the growth and xylary development of Phleum pratense seedlings resulted in her first publication in the American Journal of Botany (1948. 35: 706-715). Helen spent the next three years with David Goddard in the Botany Department at the University of Pennsylvania, where she received her Ph.D. in 1951. Her doctoral research showed cytochrome oxidase and succinic dehydrogenase in pea mitochondria and was among the first research on cellular localization of enzymes in plant tissues using differential centrifugation of cell-free homogenates. Her first review in the Annual Review of Plant Physiology (1959. 5: 115-132) entitled "Localization of Enzymes in the Cells of Higher Plants" and co-authored with Goddard, established Stafford as an authority on this subject.

Helen's next three years were spent as a post-doctoral scholar at the University of Chicago where she worked with Birgit Vennesland studying NAD+/NADP+ dependent dehydrogenases acting on hydroxyacids in plants. At that time, the relationship of these organic acids (found only in plants) to the di- and tricarboxylic acids of the Krebs cycle was not at all clear. During that time she also taught general plant biology, one of five sequential biology courses in the fabled undergraduate College at Chicago. Helen's research at Chicago resulted in several papers on plant dehydrogenases, including the first publication on alcohol dehydrogenase in plants.

Helen's ability both to teach bright science undergraduates and to conduct research publishable in leading journals, made her a prime candidate for an assistant professorship in the Department of Biology at Reed College in Portland, Oregon. She joined that department in 1954, at a time when the small biology program (three faculty) was being reorganized, slowly expanded, and its goals undergoing unique changes. Along with a few far-sighted colleagues, she helped design a highly successful, research-intensive training program for undergraduates involving faculty members who also would maintain a vigorous research program. New staff members were chosen for their teaching abilities as well as for their potential to conduct research that was funded by NSF, NIH, and private sources. Helen obtained her first NSF grant in 1955, and received continuing renewals thereafter, until one year after she retired in 1987. With such support, Helen produced a body of excellent work in an institution that has no graduate degree programs. However, every student at Reed is required to do a senior's thesis, and most of her later co-authors were students who have gone on to graduate school and are now productive scientists in their own right.

At Reed, Helen continued working on organic acids in plants, especially the aromatic phenolic acids that serve as precursors of lignin. This directed her attention to that biopolymer for a few years. Following a sabbatical year (1963-1964) as a NSF Senior Postdoctoral Fellow in Ted Geissman's laboratory in Chemistry at UCLA, Helen's interests centered on flavonoids, especially anthocyanins. This research led to her second "annual review" article on the metabolism of aromatic compounds (Annual Review of Plant Physiology. 1974. 25: 459-486). Through examination at different levels-the enzymes involved, their cellular localization, the biosynthetic sequences involved, their physiological role(s)-her efforts have contributed major concepts to the better understanding of aromatic compounds. Helen was the first plant biochemist to postulate that secondary biochemical pathways can be compartmentalized within multi-enzyme complexes (Recent Advances in Phytochemistry. 1974. 8: 53-79). This was a major advance because such a hypothesis could account for the often-massive flow of carbon from photosynthesis into plant products without reactive intermediates undergoing wasteful side reactions. Helen also proposed that those pathways that involve metabolic "grids" offer opportunities for metabolic regulation. These two concepts are discussed in detail in her treatise on flavonoids (Flavonoid Metabolism. 1990. CRC Press).

In the preface to her book, Helen identifies a second major shift in her research interests to proanthocyanidins (condensed tannins) after she spent a sabbatical with T. Cheng at the Oregon Graduate Center in Portland. Two reviews, resulting from her numerous research papers on these complex substances in the following decade, have clarified information about their structures, biosynthesis (Chemistry and Significance of Condensed Tannins. 1989. R. W. Hemingway and J.J. Karchesky, eds., Plenum Press), and their relation to lignin (Phytochemistry. 1987. 27: 1-6). Because her career in plant biochemistry and physiology has been both broad and deep, Helen continues to write stimulating papers such as those listed at the end of this biography.

In addition to her teaching and research career at Reed, Helen Stafford has served the plant sciences in numerous ways. She was a member of the editorial board of Plant Physiology for nearly 30 years (1964-1992). She was a CUEBS Commissioner (1968-1971) and a member of the NSF panel on metabolic biology (1973-1975). Helen has served as president of the Phytochemical Society of North America (1977-1978) and Editor-in-Chief (1989-1993) of its serial publication Recent Advances in Phytochemistry. This series has chronicled research in plant biochemistry for 32 years, especially in the area of plant natural (secondary) products. In 1996, Helen received the Charles Reid Barnes Life Membership Award of the American Society of Plant Physiology.

As a distinguished woman pioneer in plant biochemistry and physiology, Helen has been aware of unequal treatment for women in science. She was the first woman allowed to teach male botany students at the University of Pennsylvania in 1949. At Reed, she was the only female faculty member in the sciences (Mathematics, Physics, Chemistry, and Biology) for many years. Today there are three women among 10 faculty members in Biology.

In summary, Helen Stafford is not only recognized internationally for her research, but also as an influential teacher in one of the country's premier undergraduate colleges. She has shown her students the excitement, pleasure, and rewards of having a distinguished research career.

Eric C. Conn, University of California, Davis

2008 Phytochemistry Pioneer Award PPT

Some Papers of interest by Helen Stafford

Flavonoid Evolution: An Enzymic Approach (Plant Physiology. 1991. 96: 680-685).

Anthocyanins and Betalains: Evolution of the Mutually Exclusive Pathways (Plant Science. 1994. 101: 911-98).

Metabolism and regulation of Phenolics: Gaps in our Knowledge (in: Phytochemicals and Health, Current Topics in Plant Physiology. 1995. 15:15-30).

Teosinte to Maize: Some Aspects of Missing Biochemical and Physiological Data Concerning Regulation of Flavonoid Pathways (Phytochemistry, 1998. 49: 285-293).

The Evolution of Phenolics in Plants (Recent Advances in Phytochemistry. 2000. 34: 25-54).

Birgit Vennesland, Ph.D.

Birgit Vennesland Birgit Vennesland and her sister Kirsten were born on November 17, 1913, in Kristiansand, Norway. Their father had immigrated to Canada shortly after graduating from high school, but made several trips back to Norway to woo and eventually wed their mother, a schoolteacher. The newlyweds went to Calgary after honeymooning in Germany, and when they learned she was pregnant, their mother returned to Norway to give birth in Kristiansand. Their father entered the United States to study dentistry in Chicago, where he eventually obtained his D.D.S.

As she wrote in her prefatory chapter in Annual Reviews of Plant Physiology (32:1-20 [1981]), their parents "tired of waiting for the end of World War I" and in May 1917 their mother sailed for the United Sates with her daughters to rejoin the father in Chicago. Both girls rapidly became bilingual, learning English from their friends at school while speaking Norwegian at home. Because their parents greatly valued education, their home overflowed with books, both Norwegian and English.

Vennesland entered the University of Chicago in 1930 on a scholarship awarded to her on the basis of a competitive examination in physics. Robert Maynard Hutchins, the new university president, was "reorganizing" college education, and Vennesland entered the last class operating under the "old" plan. She therefore enjoyed the benefits of both systems, and enrolled in a general science course entitled "The Nature of the World and Man". Top science faculty, each of whom gave a few lectures in their specialty, taught this course, which began with astronomy and ended with zoology. It influenced Vennesland to follow a pre-med program that allowed her a mix of the physical and biological sciences. Eventually she settled on a biochemistry major and received her B.S. degree in that discipline in the spring of 1934.

After brief employment as a research technician at the University of Illinois Medical School, Vennesland recognized her need for more knowledge. So she returned to the University of Chicago to do graduate work in biochemistry. Biochemistry in the 1930s was the chemistry of small molecules such as vitamins, amino acids, steroids and hormones that were being continuously identified. It also included aspects of animal physiology such as diabetes, gluconeogenesis, and ketogenesis. Metabolism, which would eventually clarify relationships among these subjects, was largely unknown, although knowledge of some of the enzymes involved was developing. The department's laboratory courses emphasized analytical techniques suitable for blood and urine, and in hospital laboratories some jobs were available for biochemists with such training. Vennesland selected her own thesis project, the oxidation/reduction potential of an obligate anaerobe, which she completed in 1938. During her thesis research she observed that bacteria, including anaerobes, require small amounts of CO2 to grow. This finding was to influence one of her later research interests.

In 1939, Vennesland received a fellowship from the International Federation of University Women that would allow her to work with Otto Meyerhof who was then in Paris. But the war in Europe forced her plans to change, and she went instead to Harvard to work in Baird Hastings' biochemistry department. There she joined his team studying glycogen formation with the short-lived (20 minute half-life) isotope of carbon, 11C, use of which required careful planning and speedy work-up of experiments. While the research team readily showed that 11C-labelled lactic acid gave rise to labeled liver glycogen in starved rats, the more exciting finding was the incorporation of 11CO2 into liver glycogen. This observation demonstrated that there was "a pool of metabolites that contributed to liver glycogen" that could be labeled by 11CO2. (B. Vennesland, 1991. FASEB Jour. 5: 2868.)

Vennesland returned to the University of Chicago as an instructor in the biochemistry department in 1941 where she intended to examine CO2 fixation reactions in non-photosynthetic plant tissues. However, heavy teaching loads and involvement in a malarial research project on campus, resulted in little else being done until the war finished. Then in the fall of 1946, students began to return to graduate school, and Vennesland's research program flourished. She had purchased a Beckman DU spectrophotometer, which became commercially available only after the war and was essential for measuring the oxidation/reduction of the pyridine nucleotides DPN+ and TPN+ (as NAD+ and NADP+ were then called). Her first students isolated enzymes such as yeast alcohol dehydrogenase, rabbit muscle lactic dehydrogenase, Warburg's "old yellow enzyme" and "Zwischenferment" (i.e. glucose-6-phosphate dehydrogenase); the two-last mentioned were utilized in manometric assays of TPN+. Although ATP and DPN+ became commercially available from the Pabst brewing company about that time, TPN+ had to be isolated from hog liver. This was accomplished by two of her students using a procedure of Warburg's that had been carried to the United States by Erwin Haas, one of his former technicians, and for several years Vennesland's laboratory was the only source of TPN+ outside of Germany. Samples were given to such investigators as Leonard Tolmach who, working in James Franck's and Hans Gaffron's photosynthesis laboratory at Chicago, independently discovered that TPN+ could act as a Hill-reagent and be reduced by spinach grana in a light-dependent reaction. Also, Severo Ochoa and his postdoctoral associate, Arthur Kornberg, received TPN+ with which they examined malic enzyme in animal tissues.

Equipped with such enzymes and their coenzymes, Vennesland and her students began examining reactions of intermediary metabolism in plant tissues. (She intentionally avoided examining reactions that might be involved in photosynthesis because there was general agreement that research groups at Chicago should not compete with each other.) As a result papers and reviews describing research in plant tissues on the following enzymes appeared during the 1940s, 1950s and 1960s: TPN+-malic enzyme; alcohol, formic acid, glucose-6-phosphate, phosphogluconate, glucose, D-glyceric acid, and dihydro-orotic acid dehydrogenases; glutathione reductase; PEP carboxykinase; TPNH oxidase; dihydroxyfumaric and hydroxypyruvic acid "reductases"; and glyoxalate carboligase.

In 1950 Vennesland and Frank Westheimer, then in the chemistry department at the University of Chicago, initiated a collaboration that greatly advanced our knowledge of the reaction mechanism of the pyridine nucleotide dehydrogenases. In their first experiments, they and their students showed that the two hydrogen atoms at carbon-4 of the dihydropyridine ring of DPNH and TPNH (i.e., NADH and NADPH) are enzymatically non-equivalent, and that these dehydrogenases transfer hydrogen (as hydride) stereospecifically between substrates and coenzymes. This was the first experimental demonstration of the enzymatic inequality of the two enantiotopic hydrogen atoms on the methylene carbon atom of ethanol (see TIBS, 3:265-8 [1978]). It made possible the enzymatic synthesis of a pure enantiomorph of ethanol-1-d. This discovery also permitted the classification of pyridine nucleotide-linked dehydrogenases into two groups. The A-stereospecific enzymes remove the hydrogen at the pro-R side of the dihydropyridine ring, while B-stereospecific enzymes transfer the pro-S hydrogen. This work therefore represented an early example of the non-equivalency of the two identical groups on a pro-chiral carbon atom when an enzyme acts upon substrates containing such atoms. Numerous papers on the enzymatic transfer of hydrogen, and the stereospecificity of enzymes involved resulted from this research. A stimulating review on stereospecificity in biology and the Ogston hypothesis is authored by Vennesland in Topics in Current Chemistry, 1974. 48:39-65.

With the departure of Gaffron (and the death of Franck), research on the "light" reactions of photosynthesis terminated in their laboratory. Vennesland then began work on the Hill reaction, showing that CO2 was required. Research in her lab in the 1950s and 1960s therefore broadened considerably as she and her students took up this new area but continued to examine plant intermediary metabolism and the stereochemistry of enzymes. (A list of many of her papers can be found in the chapter regarding Vennesland in Women in the Biological Sciences, a bibliographic sourcebook, 1997, L. S. Grinstein, et al. eds. (Greenwood Press, Westport, CT)). By 1968, Vennesland's many research accomplishments had been recognized by her receipt of the Stephen Hales Prize of the American Society of Plant Physiologists (1950), an honorary D.Sc. from Mount Holyoke College (1960), and the Garvin Medal of the American Chemical Society (1964).

Vennesland's investigations of the Hill reaction of photosynthesis, and some shared views and common methodologies, led to several extended trips to visit Otto Warburg at the Max Planck Institute for Cell Physiology in Berlin during the early and mid-1960s. These visits resulted in an invitation from Warburg to join the Institute as Director (and his handpicked successor). She therefore left the University of Chicago in 1968 and moved to Berlin. Promises and expectations were apparently not fulfilled and conditions (scientifically and personally) worsened after her move to Berlin. The Max Planck Gesellschaft came to her rescue and arranged for her move, in 1970, to a nearby Max Planck Institute, designated the Forschungsstelle Vennesland (literally Research Place Vennesland). Before this move, she had become intrigued with the possibility that the controversial quantum yields reported by Warburg could be attributed, in part, to the presence of nitrate in the medium. This led to her interest in the process of nitrate assimilation in photosynthetic organisms, and to her pioneering work in this and related areas from the early 1970s until her retirement in 1984. Some noteworthy accomplishments during this period were the first complete characterization of assimilatory nitrate reductase (quaternary structure, identity and stoichiometry of prosthetic groups, and site of regulation); identification of cyanide as a natural metabolite in photosynthetic organisms and as a physiological regulator of nitrate assimilation; and metabolic routes for cyanide formation in photosynthetic organisms. For example, she found that cyanide is a major end product in the oxidation of D-histidine, catalyzed by D-amino acid oxidase. Postdoctoral associates who trained with her during this period carried on some of this work.

After retirement, Vennesland moved to Hawaii where her sister Kirsten, a M.D., had gone in 1967 as the tuberculosis control officer for the U. S. Public Health Service. Following Kirsten's death in 1995, Birgit Vennesland moved to a retirement community in Kaneohe, HI. Following a short illness, Birgit Vennesland died on October 15, 2001.

Birgit Vennesland was a remarkable scientist as evidenced by the breadth and originality of her research. She was an outstanding role model who had a lasting influence on the many students and postdoctoral associates who worked with her over the years. Her fascination with science and approach to research were contagious. A large number of these students and postdoctoral associates went on to successful careers at prestigious institutions in the United States and abroad, including two members of the National Academy of Sciences (USA).

Eric E. Conn, University of California, Davis
Larry P. Solomonson, University of South Florida

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