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Iris Köhler

Last week’s orange moon was now a silver sliver in the night sky, and Iris Köhler swatted away swarms of mosquitoes from her head lamp as she snipped soybean leaves from a large spread of crops near Champaign-Urbana, Illinois.

Researchers from around the world come to this University of Illinois experimental site called SoyFACE to investigate a question of growing concern to agriculturists and climatologists alike: how might a rapidly warming climate and elevated carbon dioxide levels impact crop production for future generations?


Iris Köhler, a postdoctoral researcher in the USDA-ARS Research Participation Program, spent two years studying the impact of projected carbon dioxide and temperature levels on genetically modified soybean yield. Above, she rests after harvesting soybeans.

Köhler, who holds a Ph.D. in plant ecophysiology from the Technische Universität München in Germany, spent two years helping find answers as a participant in the Research Participation Program for the U.S. Department of Agriculture (USDA) Agricultural Research Service (ARS). 

The USDA-ARS Research Participation Program provides opportunities for students, postgraduates, established scientists and faculty to participate in programs, projects and activities at ARS-designated facilities to help ARS solve agricultural problems of high national priority. The program is administered by the Oak Ridge Institute for Science and Education (ORISE), which is managed by ORAU under a contract with the U.S. Department of Energy. 

The program prepares a diverse and highly talented pool of scientists and engineers to address science, technology and policy issues. The program also enhances the future scientific and technical workforce to be both knowledgeable and trained in fields of specific interest to ARS. 

Köhler cultivated a love of agriculture as a child vacationing on German dairy farms with her grandparents. She was sitting in a camper van during a farming internship in Victoria, Australia, when she received an email from her Ph.D. advisor with a link to a call for applicants for the ARS opportunity.  

“I was thinking a lot about how to combine my interest in practical agriculture with my interest in science,” said Köhler. “Conducting research at an amazing university with world-class scientists on basic agricultural questions was exactly what I had been looking for.” 

Köhler conducted research under her mentor Carl Bernacchi, Ph.D., in the Environmental Plant Physiology Lab in ARS’ Photosynthesis and Global Change Research Unit. She helped grow two different types of soybeans: normal, “wild-type” soybeans, and soybeans genetically modified to have more of a certain enzyme, sedoheptulose-1,7-bisphosphatase.

This enzyme plays a critical role in the Calvin cycle, a process used by plants to convert carbon to glucose for food. Köhler and others at SoyFACE wanted to know how these genetically modified soybeans would react to elevated levels of carbon dioxide and temperature compared to their non-genetically modified counterparts.

“Ultimately, researchers at SoyFACE are helping ensure we will have enough food in the future,” said Köhler.

The soybeans were grown side-by-side under four experimental treatments: a controlled setting, one with projected carbon dioxide levels for 2050, one with projected temperature levels for 2050, and one with both elevated carbon dioxide and temperature levels.

The experimental process was exhaustive, demanding both field and lab work during nonconventional hours of the night and day. For example, to accurately collect data on soybeans’ photosynthetic responses, Köhler collected leaf samples before sunrise and stored them in a cool, dark room until processing time. She then “woke up” the leaves by placing them under a strong light source before taking measurements. 

“Sure, working at crazy hours like 3 a.m. during the field season was tough,” said Köhler, “but with the right spirit and support from my peers, I got the job done and was proud of myself and the results.”

These results, which Köhler co-published in the Journal of Experimental Botany in December 2016, indicated the wild-type plants suffered yield losses while the modified plants maintained their yield levels under future climate projections. This was a promising finding for future crop production.

Köhler credits her two years in the program with improving her leadership, research and scientific communication skills.

“When I joined the program, I believe I still had a kind of student-mindset, expecting to a certain degree to be told what to do, and whether or not a decision is right or wrong. I feel now that I’ve become a truly independent scientist and mature adult able and willing to take on leadership positions and discuss science eye-to-eye with senior scientists,” said Köhler, who influenced several undergraduate students in their own research projects at the lab in addition to planning and conducting research independently. 

Köhler enjoyed the leadership aspect of the program so much that she decided to serve as co-chair of the University of Illinois Carl R. Woese Institute for Genomic Biology Postdoctoral Association, which pairs early-career scientists with personal and professional growth opportunities. The experience here solidified her appreciation of working with students and helped secure her current position as a graduate school coordinator at the Helmholtz Centre for Environmental Research in Leipzig, Germany.

In addition to broadening her mind to other career possibilities, the program also increased her appreciation for cultural diversity.

“I met amazing people at the lab and am deeply convinced that, if more people would travel, live abroad and truly immerse themselves in a different culture, we would see a greater acceptance of individuals different from ourselves,” said Köhler, who developed close friendships with team members from around the world. “I hope ORAU will continue with these incredible programs in the future. It’s not just about doing great science, it’s so much more, and I’m grateful that I could be a part of it.”