Richard Zobel

BS in Chemistry 1965 and teaching certificate in High School Math and Science in 1966 from what is now California State University at Sacramento; MS in Vegetable Crops from University of California at Davis (1969); PhD in Genetics from University of California at Davis (1972); Post Doc at Harvard University (1972-1974); Research Scientist at Monsanto Chemical Company (1974-1977; member of first biotech group); Post Doc, assistant Professor, Associate Professor, and Professor, Cornell University (1977-1997); Research Geneticist with ARS (1978-1997); Plant Physiologist with ARS, Appalachian Farming Systems Research Center, Beaver WV 1997-present.

From the beginning of my career, I have conceptualized plant growth and development in a wholistic fashion; this is part of what led to my long term collaboration with Don Wallace at Cornell. From the beginning, it was obvious that the root system was very poorly understood, and most attempts at whole plant modeling resorted to a modified black box method to deal with roots. A lack of solid, predictive, data and hypotheses is the obvious reason for this problem. In attempting to resolve some of this, I developed aeroponic techniques to be able to provide the roots with a realistic rhizosphere (ignoring physical constraints) while still being able to visualize and manipulate root growth. When excavating roots in the field, the spatial and temporal variability became obvious, so we developed statistical techniques that could deal with the resulting genotype by environment interaction in a realistic fashion. This lead to analysis methodology that surpasses multiple regression in being able to derive predictive models. Variants on this methodology can out perform geostatistics in dealing with spatial variation. Along the way, we developed soil environment measuring technology, which was rapidly superceded by developments in the instrument industry.

None of the above directly addressed the problem of what constitutes a plant root system, and how it functions. My early research discovered that although the botanists considered root systems to be made up of three types of root, they were really made up of at least four types. Subsequent research in other laboratories has extended this to at least 6 genetically distinct types of root that can be identified on morphological or developmental grounds. A major portion of my research in the 80’s and 90’s was focused on identifying environmental and genetic parameters which interact to produce the functioning root systems found in the field. More recently I began to address the question of whether these different types of root are functionally different. We confirmed that different types of root function in different temporal/developmental spheres and demonstrated that the spatial pattern of function (relative to the root surface), and possibly even the kinetics of the different functional characteristics, differ between root types, as well as between genotypes. The obvious conclusion is that analyses and models that restrict themselves to whole root systems, without taking into account these different types of root, significantly under estimate the diversity of functional responses, and therefore can not reliably predict responses to changing environments.

Some of my research and that of others suggests that the root system plays a controlling role in the developmental processes of the shoot. Thus, the lack of predictability of root function translates to a lack of predictability in shoot development and function when changes in rhizosphere environment are encountered. My recent research has demonstrated that the finest roots of most plant species, while providing 90% of the root length and surface area, are the least understood. We have demonstrated that these normally short lived (2 +/- weeks) roots can change in diameter, mass density, longevity, and length in response to changes in their environment. In addition, we have shown that, when classified by average diameter, there are two or more distinct populations of these roots on an individual root system, and that they may have distinctly different responses to the same environmental stimulus. This is the focus of my current research – functional, morphological and anatomical responses of fine roots to a changing environment. .