Dedication: Theodore DeJong

Theodore DeJong

Professor Theodore (Ted) DeJong has had a long and distinguished career in the broad area of whole tree physiology, with a particular emphasis on stone fruit species (peach, plum, and nectarine) that are relevant to California but widely grown in many areas of the world. This research has led to an enhanced understanding of tree growth and development, especially in areas relating to carbon balance in the tree, tree architecture, and the growth of the vegetative canopy, fruit, and roots. He has focused considerable effort on modeling these various processes. In addition, he has been a leader in an effective stone fruit breeding program.

Ted grew up in Ripon, CA and spent a good deal of time working on peach and almond farms in the area - he had loved farming ever since he was in grammar school. Ted attended Ripon Christian Schools and then Calvin College in Grand Rapids, Michigan. While in college he became interested in ecology and, because of his farming experience, was mainly interested in plant ecology. After college, in 1968, he married his wife Rose, and was scheduled to be drafted into the army and so he volunteered for admission to the Army Officer Candidate School. He graduated from OCS in late 1969, was commissioned, spent most of the next year in Fort Riley, Kansas, and went to Vietnam on September 11, 1970.

In September, 1971 he enrolled in an M.S. program at Fullerton State University in Plant Ecology. His mentor there was Dr Ted Haines and he was probably most influential in Ted subsequently choosing an academic career. In Jan, 1974 he enrolled in the Botany Ph.D. program at the University of California, Davis to continue studying Plant Ecology with Prof. Mike Barbour. His research was on the physiological ecology of Californian beach and dune species.

In January, 1978 he began a one-year post-doctoral fellowship at the Smithsonian Institution and did research on the physiological ecology of tidal marsh species. One year later, Ted returned to UC Davis on a Post-Doctoral Fellowship in the Agronomy and Range Science Department with Prof. Don Phillips working on carbon and nitrogen assimilation interactions in legumes. At this time, he realized that he could have a rewarding career working in "applied environmental physiology of crop plants," otherwise known as "crop physiology."

He was appointed as a Lecturer/Pomologist/Co-op Extension Specialist at the Kearney Agricultural Experiment Station and Extension Center (KAC) in the Pomology Department in April 1981. Thanks to good field staff support, he remained at Davis but conducted virtually all of his research and extension work at KAC for the first 25 years of his career. He was assigned to teach practical pomology courses at Davis and also co-taught graduate level courses in plant/crop physiology. He enjoyed teaching and by the end of his career he was the main instructor for the pomology/tree crop physiology courses at UC Davis, even though he had never taken a formal pomology or horticulture course in his life.

His teaching had a lot of influence on his research because, early in his career, as he was teaching some of the pomological "dogma" to his students, he realized that some of it made little physiological/ecological sense. Furthermore, many of the current horticultural practices were often not backed up by sound scientific study, so some of these "dogmas" formed ideas for research. Such ideas led to investigating: the importance of leaf photosynthetic capacity in determining crop yield; fruit effects on photosynthesis; causes of the double sigmoid growth of stone fruit; carbohydrate and nitrogen allocation in fruit trees; carbohydrate storage in trees; causes of alternate bearing in fruit trees; physiological mechanisms involved in size-controlling rootstocks; factors driving shoot growth in fruit trees; and interactions between fruit, shoot, and root growth in fruit trees.

Ted's challenges to much of this "dogma" within the teaching framework have also been widely acknowledged internationally. New Zealand pomologist Dr Stuart Tustin states that "Ted's incisive consideration of the science presented within the ISHS Fruit Section has always been highly valued by symposia participants, as has the friendly pugilism often arising in such discussions with Ted in such fora. He can always be relied upon to challenge concepts and interpretations and in such ways, contribute greatly to the scientific thinking and advances in fruit crop pomology and physiology."

When he was a graduate student at UCD, he attended Prof. Robert Loomis's crop ecology lectures for two years in a row and was fascinated with his crop modeling work. When Ted had his first sabbatical opportunity in 1987, he went to Wageningen University in the Netherlands to learn more about developments in that field of research. This was a watershed experience for his career. While there, he realized that plants can best be viewed as composite organisms made up of semi-autonomous organs and the key to understanding/modeling whole plants was in understanding what drives the growth of those individual organs. This also led to development of a new model for explaining stone fruit growth patterns. After this sabbatical, much of his conceptually-based research involved various aspects of crop modeling and the culmination of this work resulted in development of Functional-Structural Plant Models of peach and almond tree growth and physiology. The L-Peach and L-Almond models are still the most detailed and advanced virtual computer simulation models of fruit trees in existence today. They permitted the testing of, and/or demonstrated concepts behind, numerous fruit tree management practices that are commonly used in commercial fruit production.

Underpinning Ted's work in crop modeling at the Department of Pomology (later Department of Plant Sciences) at UC Davis, was a range of research that focused on understanding tree physiological and orchard management factors that control the carbon balance/budgets of fruit and nut trees. His initial work focused on understanding the functioning and photosynthetic efficiencies of tree leaves and on understanding factors governing the horticultural efficiencies of orchard canopies. As he gained experience and understanding of factors controlling the "supply side" of the carbon balance equation, later studies focused on the "demand side" of the equation and the integration of both aspects into a functional understanding the how tree carbon budgets work. This "demand side" work focused on characterization and understanding factors governing flowering and fruit set, fruit growth, vegetative (leaf and shoot) growth, and root growth, and eventually involved numerous studies characterizing how rootstocks control shoot growth (see Horticultural Reviews 46:39-97 for this latter topic). Much of his intellectual stimulation for conducting the various aspects of this research came from an overall goal of developing an integrated understanding of fruit tree carbon budgets and growth through crop modeling. As indicated above, this led to the development of very sophisticated and complex functional-structural tree simulation models that are not only carbon budget models but also include integrated understanding of the architectural development of fruit trees.

French scientist, Dr Evelyn Costes, notes that: "with an an open-minded vision Ted has combined skills in plant physiology, classical horticulture and fruit tree cultivation with new technologies involving computer programming and modelling. He thus has made an exceptional research contribution."

Italian colleague, Dr Paolo Inglese, states that: "personally I gained a lot of inspiration from his papers on fruit growth and development and carbon partitioning in peach trees. I really learned a lot and, most interesting, it became easy to move from physiology to orchard management, understanding the basic factors of tree behavior. From this point of view, it is clear how strongly Ted DeJong influenced a large number of students, and younger scientists worldwide, with an impressive benefit for horticultural development, in terms of knowledge and, most importantly, field practices and orchard management. Indeed, it is worth noting that Ted's research was always related to real problems experienced by stone fruit growers, particularly peach and almond growers. He is strongly dedicated to solving real problems through a clear scientific standpoint and this deserves our admiration. I have seen Ted giving lectures several times, but I have also seen him talking to growers in the field ready to learn and to share his knowledge as well as to understand the basic facts behind any particular horticultural technique."

Pomology Farm Advisor, Rachel Elkins, summarizes Ted's research achievements as follows: "Ted's successful career reflects his thought process: creativity melded with logic and practicality. His upbringing on an almond farm in the Central Valley provided the necessary 'grounding' needed to ensure his research and extension contributions would impact commercial agriculture. His training in basic biology and ecology have provided the unique holistic perspective enabling him to think 'out of the box' about fundamental perennial crop physiology concepts. Those of us fortunate enough to take classes from him, study under him, and work with him have benefitted enormously. Indeed, the concept Ted has...