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Cactus Odyssey

Cactus Odyssey
jdmIn January of this year, biologist James Mauseth published the fourth edition of his textbook, Botany: An Introduction to Plant Biology. It draws on his more than three decades of research and teaching in the field of plant biology, and in particular on the insights he’s gleaned from the study of cacti.

I sat down with Mauseth, a professor of integrative biology, to discuss what makes a good textbook, what he’s learned about teaching science to undergraduates, and why the cactus hasn’t gotten quite the attention it deserves.

Daniel Oppenheimer: What pushed you to write the textbook in the first place?

Dr. Jim Mauseth: I was teaching BIO322, the Structure, Physiology, and Reproduction of Seed Plants, and was unhappy with the text I was using. It was all terms and definitions. It wasn’t explaining why it was important to learn the material. What I realized is that there are stories to tell the students about why plants are the way they are. Why does a particular plant evolve this way, and not that way? Why does this tree have simple broad leaves but this other one has compound leaves with tiny leaflets?

I always teach my students, and I’ve tried to get this across in the textbook, that the two most important questions are: What are the alternatives? And what are the consequences?

Elaborate on that a bit.

Well, what’s the alternative to having a leaf? It’s not having a leaf, or, like cacti, having leaves so tiny that in effect you don’t have leaves.

What are the consequences of having leaves versus not? Leaves catch more light, and so they can photosynthesize faster, but they also lose water faster, so they tend to not be very desert-adapted. Really tiny leaves can’t photosynthesize as fast, but they don’t lose as much water.

Insects can land on leaves and start eating them and laying eggs in them. Big leaves are very visible to herbivores, and so they can come over and start eating them. A leaf can act as a sail, and can tend to make a plant blow over in the wind. But when you don’t have leaves, spores don’t land on you as easily. Insects have nothing to land on. They don’t catch wind, and don’t tend to blow over. No deer is going to come over and eat cactus leaves that are so small. Why bother?

Is it difficult to get students interested in plants?

I don’t think so. You just have to explain it to them in a way that makes it relevant. Most college kids know a huge amount of human biology, even if they’ve never taken a class about it. So I’m always trying to explain plant biology in the context of human biology. I’ll ask the students, for instance, how many arms do they have? How many legs, brains, kidneys? And then I’ll ask: How many plants have so few of anything? They have hundreds, or thousands, of leaves. They have hundreds, or thousands, of flowers.

When we’re fetuses, we grow our arms and legs and kidneys and so on, and that’s about it, with a few exceptions. Plants, on the other hand, have lots of temporary organs, and they grow them throughout their lives.

What are the consequences of these two alternatives? Well, as we get older, our eyes get worse and worse. Our heart gets worse and worse. Our brain starts to slow down. Our digestive system can’t handle spicy foods anymore. There are bristlecone pine trees, on the other hand, that are thousands of years old. Each year they make brand new needles, so they have brand new feeding system every year. Every year they make brand new sections of root. There’s a story there, and there are alternatives and consequences.

Speaking of stories, why did you decide to study cacti in the first place?

It would be nice to say that after carefully considering the aspects of botany that needed to be studied, and contemplating how to best approach the pressing issues in the field, I came up with cacti as a model organism. It wasn’t that. I went to graduate school in Seattle at the University of Washington, where it rains all the time. During my first spring break, I went on a field trip to Arizona, and really noticed cacti for the first time. I became intrigued by them. They’re so different from other plants.

My advisor was good enough to say, “Well, go ahead and investigate them. See if something important comes up. If it turns out that there’s nothing interesting or tractable then move on to something else, but go and look.” Fortunately, a really interesting problem did come up. And that led to another problem, and then another, and here I am, still studying cacti. But it started because I just liked the plants.

Has your interest in cacti affected the textbook in any significant ways?

I think I’m more interested than most plant biologists not just in cacti, but in non-flowering plants like algae, mosses, ferns and liverworts. These are fascinating organisms that haven’t always gotten so much attention because, historically, biology and botany textbooks have tended to focus on plants and animals that are common in Europe, which is where the natural sciences got started. There are questions like, “How do plants deal with winter cold?” that make sense in those climates but not so much in warmer climates. In Texas, for instance, droughts are a much bigger deal for plants than winter cold. If botany had been pioneered by someone living in the Amazon rainforest, we would be coming from a whole different perspective, and I try to take that into account.

How different is this edition from the first edition?

Totally different. I realize now that I was very inexperienced then, so rather than just update the book, I wanted to basically start anew, to completely re-write and re-organize everything that could be clarified to make it easier for students to learn the material.
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Tuesday, 07 February 2023

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