The Dangerous Parsnip

Creating a stimulating introductory-level science course is challenging. There’s a host of information thrown at students: terms to memorize, concepts to learn, lab techniques to familiarize oneself with. The prospect is daunting for some, terrifying for others. These courses are challenging and rigorous, especially for those who have no previous science background. It’s not for nothing that BIOL 145: Cell Biology and Genetics is often referred to as “Cell Hell.”

What is frustrating for science teachers is that the true nature of science can easily be lost in an introductory course. They are what Senior Associate in Science Instruction in Biology Vickie Backus calls “cookbook labs, where everything is laid out for you and you add one thing to another to get a purple liquid, and then you add a third thing and it blows up, and all that is expected.” In cookbook labs, there are right answers and wrong answers, and any deviation from expected results is abnormal.

But Associate in Science Instruction in Biology Susan DeSimone is dissatisfied with this strict format because “science that has been done by eighteen-thousand people before you, where you are trying to [derive] the answer you are supposed to get … that’s not real science.” DeSimone and Backus have been searching for alternatives for the introductory-level biology labs, particularly Cell Biology and Genetics, for some time.
They think they may have found the answer in the wild parsnip. It is an invasive, wild type of root vegetable that was once a staple crop in the northeast. The wild parsnip is becoming a serious problem in Vermont.

Middlebury College’s Landscape Horticulturist Tim Parsons writes in his blog “The Middlebury Landscape” that the parsnip is “a biennial — a rosette of leaves the first year, and flower stalks the second” that is particularly difficult to eradicate because “biennials are hell-bent on flowering in their second year… cut [them] down too early, and they form many smaller flowers, and therefore more seeds, than [if] left untouched … It thrives on roadsides, and in other poor growing locations because the rosettes are poor competitors in their first year and can’t keep up with a healthy stand of vegetation, such as grass ... Seeds of parsnip are viable in the soil for up to four years, so vigilance is required.”

The parsnip is not only a problem because it’s invasive and difficult to eradicate; it is also toxic. “It is a different toxin than poison ivy,” DeSimone said. “Poison ivy is an immune reaction, an allergic reaction. Wild parsnip works in a different way. As we understand it, everyone is susceptible to wild parsnip, because wild parsnip toxins are able to move directly into cells. If the tissue gets exposed to sunlight — the UV light, that’s the trigger — the sunlight catalyzes an interaction between the toxin and the DNA in the cell. And that interaction triggers cell death. What you end up seeing is a huge blister that looks like a second-degree burn, and then the skin peels away, and you’re left with a hyper-pigmentation scar — unique to parsnip burns — that can last anywhere from several months up to a year.”

Last spring, DeSimone played around in the lab and thought of better ways to teach the Cell Biology and Genetics lab just as the wild parsnip was leafing out. “[I] thought, well, what’s known about wild parsnip?” she said. “It’s important to have something relevant for students, and parsnip is definitely relevant for [anyone living in Vermont]. So I did a literature search. And it turns out there isn’t a lot known about it.”
The more DeSimone looked into wild parsnips, the more excited she became about its potential to revolutionize how the BIOL 145 lab is taught. “The challenge is finding a system where you can start to do some interesting questioning, but at the same time, find some real data,” she said. “I’ve been searching for that system since I’ve started teaching. And I think parsnip is it. [With the parsnip], we can take some relatively simple tools to start studying this, and almost any question people will come up with will be a novel question.”

DeSimone and Backus are now growing parsnips both in the lab on the fourth floor of McCardell Bicentennial Hall and in the greenhouse. They are examining wild and cultivated parsnips for differences in physical appearance, toxin concentrations and toxin components. Backus is also integrating the parsnip into one of the invasive species lab in BIOL 140: Ecology and Evolution.

“There has been a feeling in the past that what happens in the Ecology and Evolution course is in no way related to what happens in the Cell Biology and Genetics course — that these are completely different tracks, and so, why should I take both courses if I’m only interested in one of the fields?” Backus said. “What [the parsnip] is allowing us to do is bring [the two courses] closer together, so that the knowledge you gain in 140 can translate over to 145 and vice versa.”

According to teaching assistant for Cell Biology and Genetics Alison Cook, “poison parsnip is a good research topic because it is tangible. A lot of students have come into contact with poison parsnip whether they realize it or not, and understanding some of the science behind the resulting burn on a molecular or cellular level is fascinating. Research in this field is relatively limited, so students are actually exploring hypotheses that haven’t even been published yet. It gives the course a very real-world-science kind of feel.”

Backus expanded on this “real world science” feel: “[We’re doing real] research. We have no idea what’s going to happen with this stuff. It’s a challenge. Sometimes the data are messy. Sometimes the data produce internal contradictions. Part A and B lead you to opposite conclusions, and you have to somehow reconcile it. That’s what we do as biologists, as professional scientists. If you knew what the answer was, you wouldn’t be doing the experiment. It is akin to the kind of research you’d be doing in graduate school. You walk in, and there is something known about the system, some expertise in the lab, but you are finding not only the new answer, but the new question. You have to put together information and build on it in order to make something.”

The emphasis with this parsnip project is that the students in an introductory class are driving research forward in a novel area. But how successful is this novel approach compared to the old cookbook approach?

DeSimone noted that in recent conferences with students, “I had ten percent of my students who were totally jazzed. [They thought,] ‘OK, we don’t actually know the answer. I can really start to think. I’m not looking for the right answer — I’m looking for the logical answer as a possible explanation to take the work further.’ It is going to be a blast to teach, and way more meaningful for the students.”