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The Mass Media

The Mass Media

The Mass Media

Plant Sex Study Underway to Eradicate Invasive Knotweed

Gathering weeds at T stops may not sound like a rich intellectual experience for biology majors. For the students involved in Prof. Kesseli’s latest phase of invasive plant research, it’s a complex challenge in population biology that involves the uncertainties of research design and advanced genetic testing techniques.

Launched this summer, the knotweed project aims to look at the ways that a pesky and familiar plant called Japanese knotweed (Fallopia japonica), can spread with abandon and evolve into new species that out compete native plants.

“Japanese knotweed is a threat to natural plants and to diversity,” says graduate student Melinda Gammon whose thesis is on the topic. “We want to understand how it breeds. Then we can get a more realistic control plan.”

The plant reproduces clonally for the most part, she explains. “If you chop it in half, you have two plants.” Recent research has revealed that it also makes seeds (i.e. reproduces sexually), in the U.S. at least. Japanese knotweed is dioecious – an individual plant produces either seeds or pollen-as ginkgo trees do. Could knotweed propagate a third way, by hybrizing with other plant species?

To answer the question, biology major Cindy Kalkwarf has collected leaf samples from over 100 knotweed plants from around Boston and noted their exact locations by global positioning (GPS). She’s catalogued their physical details and will return to look at their growth patterns in the future.

Student researchers must consider the ways knotweed may reproduce. A plant can have multiple fathers, i.e. be pollinated by more than one plant. It can clone itself by sending out horizontal roots that grow a separate stem. When a plant is well suited to its environment, cloning is the quick and sure way to go. Another breeding strategy to dominate a locale is by blending its genes with another species to form a hybrid. Or, a plant can evolve a new species when a single plant by fluke has double the number of chromosomes, so that it can only breed with itself or other oddballs.

To consider all these possibilities, this fall the students will rely on molecular genetics to figure out how different Kalkwarf’s samples are from each other. Electrophoresis is one test they’ll use to analyze DNA extracts, a lab technique familiar to anyone who’s taken Genetics 252.

“In class, you do it once. But in this research, you do it again and again, and you get good at it,” said Kalkwarf.

The group will also use Polymerase Chain Reaction (PCR) tests to amplify tiny pieces of unknown DNA.

“PCR is like a little Xerox machine,” says Gammon. More PCR, known as Random Amplification of Polymorphic DNA (RAPD) and amplified fragment-length polymorphism (AFLP), may be needed, she says.

If all goes well, the tests will reveal just how this plant is propagating, how it might be controlled, while giving good results for two or three honors or masters theses.