Testimonials for Pioneer Member Marc Allan Cohn

Steve Footitt – Marc’s interest in seed biology, studying imbibitional chilling damage in maize seeds, started as a graduate student with Prof Ralph Obendorf at Cornel University (1973-76). Then, Ph D in hand (his “license to practice” as he would say), he arrived at Louisiana State University in 1978, where he worked on seed dormancy in red rice, a serious weed in rice-growing areas. Aware all research needs a solid foundation, he developed a simple robust test system to characterized the role of temperature and seed moisture content on dormancy. At that time there was great interest in the dormancy breaking ability of chemicals both for weed control and for understanding the mechanism of dormancy-breaking. Marc made major contributions to our understanding of how these chemicals work. He showed for the first time that nitrogen dioxide gas broke dormancy in dry seeds. He also showed the dormancy breaking activity of weak acids and bases was pH-dependent. That Marc was the first to do this in seeds was, he commented, a reflection of biologists’ general lack of education in chemistry. Investigating the chemical properties important for dormancy breaking was perhaps his biggest contribution to the field. He demonstrated that lipophilicity, functional groups, and their position, even molecular size control dormancy breaking activity. Further work showed that dormancy-breaking chemicals induced acidification of the embryo and activated metabolism prior to breaking dormancy; this refuted the anesthetic hypothesis for the dormancy-breaking activity of alcohols by showing they had to be metabolized before dormancy-breaking occurs.

The arrival of molecular biology mainly ended interest in how dormancy-breaking compounds work. But despite the advances in understanding the genetics of dormancy and identifying the large number of genes involved, we still do not know how these compounds break dormancy.
During Marcs’ career, it was noticeable that papers on seed research increasingly provided more detail on experimental systems, including the pH of test solutions. This was due to the impact of his research and the fact that he was a prolific reviewer for journals. Such was Marcs’ dedication that as the editor of Seed Science Research, he read almost every paper submitted. His enthusiasm never seemed to diminish, and to those who knew him, he was a constant source of advice (at times brutally honest) and encouragement.

Being Marc’s doctoral student (1986-92) was as challenging as it was exciting. His encyclopedic knowledge of and passion for seed biology was infectious. I also quickly realized that Jazz was the other passion in life. He was always asking questions because he was always interested in what you were doing. At one seed conference, I attended with him, over 5 days he asked every speaker a question. In the final session, the moderator (Prof Cees Karssen) asked if anyone else would like to ask the first question. He once told me “there are no answers, only better questions to ask”. As a scientist, I came to appreciate how right he was. Working with Marc opened up a whole new way of thinking.

One invaluable skill Marc taught was the forensic reading of research papers, stating the Discussion was the authors’ opinion, so look at the results as data does not lie. Marc could quickly spot missing controls and key points in the data whose significance the authors may have missed.
When designing experiments Marc was clear you needed a question and must use all possible controls to give a clear cut answer. His mantra on this was “garbage in, garbage out”. Rigorous attention to detail and record keeping in lab books, which he read, was paramount.
Changes in cell development often involve changes in cellular pH; when I had the idea of looking at changes in embryo pH as a marker of chemically induced dormancy-breaking, he encourage me to go for it. A year of hard work and failure brought me to within days of giving up. All the time, Marc advised and encouraged me and the technique was finally perfected. The next four years were truly as exciting as only science can be, as we generated unique data showing for the first time changes in seed embryo pH, metabolic activation and the metabolism of dormancy breaking chemicals during dormancy breaking. Marc encouraged debate and many hours were spent discussing what these data meant. Near the end of the project, he said to me one day “I feel sorry for the seeds because you never give up”.

Overall, as a scientist and thinker he was exceptional. A phrase he would often repeat was “seeds don’t care what we think they are doing, they just do what they do. Our job is to listen to what they tell us”. Eventually, we worked together more as colleagues. And on Fridays, Marc would occasionally join me and other grad students in a local bar for a quick beer and a game of table football. When harvesting red rice each year, he would keep the sun and mosquitoes off with a sombrero and a cigar, as we sweated away in the field. We kept in touch and occasionally met at conferences, enjoying long conversations on life. As I look back on my career as a seed biologist, I see that the insight he gave me still guides me. He gave me a chance when no one else would, for that I owe him everything.

Karen Koster – Marc Cohn was one of the first seed biologists who welcomed me into the field when I was a graduate student, and over the years, I learned to respect him as a role model, mentor, and friend. Marc was a champion of seed science and a generous collaborator who was always happy to share his knowledge and advice. He was a reliable presence at professional meetings, a supporter of our professional societies, and mentor to many young scientists. Marc’s knowledge of the history and literature in the field, his understanding of how research questions in seed biology have evolved, and his high standards and honesty about what constitutes good science made him a respected colleague whose advice and opinions were valued greatly. He is sorely missed.