Vascular function in woody plants

Dr. Pratt and team publish research in prestigious journal

By California State University, Bakersfield

August 30^th, 2021

A recently published paper in the Proceedings of the National Academy of Science isn’t the first time Dr. Brandon Pratt has had his work featured in the prestigious journal, but it is perhaps the most special time. The California State University, Bakersfield biology professor is this time publishing work that he completed alongside a team of his colleagues and students all from CSUB.

The paper, titled “Trade-offs among transport, support and storage in xylem from shrubs in a semiarid chaparral environment tested with structural equation modeling,” is authored by biology professors Dr. Pratt and Dr. Anna Jacobsen and co-authored by alumni Courtney Traugh, Mark de Guzman and Marta Percolla, all of whom have gone on to pursue a Ph.D. It focuses on how plant vascular systems function in woody plants.

“Researchers strive to publish their work in journals that are widely read so that their work has an impact on scholarship in their field of research,” Dr. Pratt said. “PNAS is one of the most high-profile journals, so it is exciting and gratifying to have a paper published in this journal. It is doubly exciting because this project is 100 percent CSUB.”

Drs. Pratt and Jacobsen previously had work published in the journal last fall as part of a 37-author international project studying drought-related tree death.

“Our previous publication in PNAS was a many authored international research effort, which was fun and rewarding to be a part of,” Dr. Pratt said. “However, this project being born, executed and brought to completion all at CSUB is a special feeling.”

In the paper, Dr. Pratt and his co-authors examine plant species found in a Southern California shrublands called chaparral and detail the various functions of the plant vascular system (or, as lay people might know it, wood) and the relationships between those functions.

“Wood that is able to perform one function exceptionally may necessarily perform poorly in another function,” Dr. Pratt explained. “For example, wood that is mechanically strong, like oak wood, is likely to be limited in its water storage capacity. The way these different functions affect one another determines many fundamental attributes of plants, such as how tall they grow, how long they live and their ability to survive drought.”

That information also tells biologists like Dr. Pratt and his team how the individual plants evolved over time, which in turn allows them to determine how long-extinct plants functioned in ancient environments and predict how current climate change could affect existing plants in the future.

“This study showed that the level of dehydration that plants experience has a strong effect on all aspects of vascular function,” Dr. Pratt said. “We knew this was important but were surprised to learn how strong of a factor it is to wood function. Wood may also be composed of different types of cells, and they occur in different abundances in different types of wood. When wood functions change, these changes are linked to changes in the abundance of different cell types, so we can ‘see’ them in the structure of the wood.”

For their research, Dr. Pratt and his team visited field sites throughout Southern California. Chaparral is a uniquely California shrublands, he said, and they contain a number of different species, which led to an especially robust analysis.

“These shrublands are also valuable for such a study because the species that thrive in this region are functionally diverse, giving us a wide variation in traits to study,” he said. “We are lucky to live in California, which hosts an amazing level of plant biodiversity. In particular, our California chaparral shrublands are highly biodiverse, so that we were able to capture many different species and a wide range of wood types and responses to dehydration.”

Funded by a National Science Foundation grant, the research and data collection has spanned many years and involved undergraduate and graduate students, as well as post-doctoral researchers. The study is an example of basic science, Dr. Pratt said, aimed at understanding how plant vascular systems function. Though it focused on a specific shrubland, what the team learned will be helpful to scientists studying other plants and regions.

“Understanding fundamental aspects of plant vascular systems is information that can help us understand, for example, why some plants are more vulnerable to drought than others, why some grow faster, and why plants have evolved in the ways that they have,” Dr. Pratt said. “The information that we learn in this study, on chaparral plants, can be applied to other types of plants and other plant communities, further tested and refined and used to inform our knowledge of plants and how they respond to stress.”