From roots to shoots

Biology alum Alex Baer publishes research on wood function throughout trees

By California State University, Bakersfield

October 27^th, 2021

While the average person might see a tree and marvel at its foliage or enjoy the cover of its shade, plant biologists like Alex Baer see endless opportunities for learning. Of particular interest to the California State University, Bakersfield alumni is how wood changes throughout the body of a tree.

As a biology graduate student in CSUB’s School of Natural Sciences, Mathematics and Engineering, Baer studied the wood of cottonwood trees and how it varies from the tree’s roots, through the trunk, and up to the tip of the shoot. Now Baer, who graduated in 2018, has had his thesis published in Journal of Experimental Botany.

“While this is not my first publication, or first time as first author, I am especially proud of getting this research published,” Baer said. “The work done as a graduate student can sometimes feel quite daunting, and there is anxiety over graduating and having research matter. It is a wonderful and lucky feeling that my thesis research was defended for graduation and then made into publication.”

Titled “Xylem biomechanics, water storage, and density within roots and shoots of an angiosperm tree species,” Baer’s research looks at how wood functions at different points within a tree, including in the belowground root portion of the plant and the aboveground shoot portion. Cottonwood trees, also called poplars, grow throughout the western United States and in science have been dubbed a “model organism” for the study of woody trees.

Wood is a complex tissue that performs many different functions necessary for trees to survive, Baer explained. Among those functions of wood are biomechanical support, physically supporting the tree’s weight, and water storage, which helps tall trees transport water upward to their canopies and stores additional water during a drought. Baer wanted to learn how these functions, as well as wood density, varied throughout the body of trees.

“I found out that root wood and shoot wood are quite different within the same tree,” Baer said. “Shoots are stronger and more tolerant to bending than are roots, which makes sense considering that they are supporting so much weight vertically. Roots, however, store more water in their wood. Root wood has a lower density, which helps explain why more water is able to reside there and why it is not as strong as shoots.

“These findings demonstrate that wood properties change with tree position to suit the needs of the tree and the physical demands of the local environment,” Baer continued. “I find bigger trees now especially interesting, where wood is tasked with holding the colossal body of a tree upright for decades to centuries, while simultaneously balancing the task of storing and moving water throughout its vast body.”

This research represents the culmination of Baer’s years of hard work in the CSUB biology graduate program. Baer first found his love of science at Fresno City College before transferring to UC Santa Cruz. There, his interest in research was piqued during an independent research course needed to earn his bachelor’s degree in biology. It was the first time he got to actually put his knowledge of the scientific process into practice, and he soon realized he wanted to keep studying plant biology as a master’s student.

At CSUB, Baer studied with Dr. Anna Jacobsen, an experience he said was extremely helpful in sharpening both his research skills and his professionalism.

“Talking with my peers was especially useful for learning to communicate more complex concepts and listen to what others were thinking about,” Baer recalled of his time at CSUB. “Asking good questions always seemed particularly useful for inspiring a lively conversation in the group.”

The master’s program also helped him improve his writing, which Baer said had been a challenge for him. He credited Dr. Jacobsen for helping him work through his struggles and become a more effective writer.

Baer’s research was part of a larger study on within-tree structure that was funded by a National Science Foundation grant awarded to Dr. Jacobsen. This meant that several studies were being conducted simultaneously in the laboratory and there was a relatively large group of both undergraduate and graduate students working together, creating a dynamic and exciting atmosphere of mutually supported science and discovery.

“Alex was a great member of the laboratory research team,” Dr. Jacobsen said. “As a master’s student, you are put into a leadership position in the lab and help to organize and plan research activities. You also serve as a mentor to undergraduates as they have their first experiences with hands-on science. Alex really stepped into this role and was an active mentor and laboratory leader.”

Now a laboratory technician for Dr. Jarmila Pittermann at UC Santa Cruz, Baer is happy to continue his work researching plant physiology, with a special focus on water transport as he did at CSUB with Dr. Jacobsen.

“I derive a lot of purpose and joy through the study and interaction with plants,” Baer said. “I get to keep working on research, and I get to keep learning as well.”