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Campus Trees Become Lab Samples in Plant Physiology Course

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Students fanned out in small clusters, using pruning shears to clip branches from jacarandas and Australian willow trees across campus.

Vandalism? No. Science.

To study the effects of the statewide drought and how it affects the plants and shrubs they see every day, students are using the campus grounds as a living laboratory — and learning key lessons about plant physiology and ecology.

For two weeks, students from the upper-division Plant Physiological Ecology class studied how the trees they see every day on campus are living and struggling with mandated reductions in campus water usage.

“I’ve worked with plants before, but not those that are around the campus,” says senior biological science major David Mancilla as he helps gather samples. “I’m interested to know about these plants and their responses to a difficult environment. It’s pretty interesting to use plants we see every day.”

“Right now, the students are looking at the trees for signs of what happens to them when water is cut off to the grass areas around them,” explains Lynn Sweet, lecturer in biological science who is co-teaching the course with Darren Sandquist, professor of biological science.

“By using the tree stems, students check for signs of stress and ‘flow failure,’ in which a plant takes in air when it can’t get water,” Sweet says. “Such action creates stress, which makes the trees more prone to disease.

“Some of the trees on campus are fairly drought tolerant, so we may see that these trees are doing just fine despite reductions in water,” adds Sweet. “This, together with the information about where trees are actually accessing water, will give a fuller picture of what the trees need to thrive, and how they access resources here on campus.”

The students also are studying the trees at a chemical level to detect the sources of water that the plants are accessing.

“That’s the value of using the campus as a lab,” explains Sandquist, who revised the course to utilize the campus in this manner. “We know the chemical ‘signature’ of the water from the water table, from rain and from the irrigation water, so we can tell where the trees are getting their water.”

The course revision was underwritten by the California State University’s “Campus as a Living Lab” grant program, established to partner faculty members and facilities management staff “in using the campus as a forum for the exploration of sustainability concepts and theories.”

Once they return to the lab, the students extract and distill the moisture from their plant samples. With other samples, they conduct tests to see how much water flows through a piece of a tree stem in two minutes. The less water, the more air blockages.

“This is why I want to be a teacher ,” says Estefani Bautista, who hopes to enter the teacher credential program after she graduates, “to be able to share with my students the experience of learning about plants through collecting samples of those growing around us.”

“These are integral learning outcomes for these students,” says Sandquist, noting the added benefit for the campus. “From their work, we can identify those trees that are most stressed, most vulnerable. We’ll be doing more research that can help facilities management cut water use while maintaining the campus landscape.”