6th Grade Science Chat: Edited Transcript
Chat with Dr. Stuart Strand, UW
January 15, 2002, 10:30 a.m.

ONeill Class: Hello, This is Mr. O'Neill's 6th grade science class. Dr. Strand, could you start by reviewing briefly your study in phytoremediation?
Dr. Strand: We started out by investigating whether poplar trees could remove toxic compounds from underground well water, the groundwater that wells reach. The compounds that we are interested in are the small molecules like trichloroethylene, which used to be used by dry cleaners and which is now the most important pollutant of groundwater. We thought that poplar trees, which have very deep roots, would pull the polluted water up and evaporate it into the air. We hoped to make the trees break down the trichloroethylene (which I will call TCE for short) by genetically engineering the trees to have enzymes that could attack the TCE. We found that even natural trees can break down TCE, but not very fast. We are still working on genetically engineered trees that break it down much faster.

Rebecca: Dr. Strand why did you decide to teach Science?
Madeline: Dr. Strand why did you want to study plants?
Dr. Strand: Actually I don't teach that much. My main interest is in the research. That's because I love to discover new ways of doing things. I am in engineering in addition to being a scientist and I like to invent new solutions to problems especially pollution problems. I get a big thrill out of new ideas.

Robert: What is your favorite part of studying plants?
Dr. Strand: I also study bacteria, which are very simple compared to plants. I guess I'm fascinated by the multiple types of tissue that plants have; the chemistry that goes on in the roots is different than that in the leaves and in the trunk. Also there is a community of microorganisms that lives around the roots that can also change the chemistry of what happens to pollutants. I am interested in trying to use these different types of metabolism, and to understand how toxic chemicals move around and are transformed by different parts of the plants.

Kris: How have the plants you've worked on been used to clean up pollution?
Dr. Strand: We have planted poplar in plantations to test the idea of removing compounds like trichloroethylene from groundwater at a site in Medford, Oregon.

Kyle: What is the most important step in the process of phytoremedeation?
Dr. Strand: The most important step in phytoremediation is getting the pollutants into the plant. Phytoremediation is being used to clean up toxic metals in soil (things like mercury and cadmium) and getting the roots to take up the metals is a challenge.

Shane: Do any plants cause pollution. ;^)
Dr. Strand: Shane, trees emit compounds called terpenes into the air. Stuff that smells like turpentine. On sunny days this can cause smog, the haze that you see in forest sometimes.

Madeline: Who was the 1st person to discover that plants could make TCE less harmful?
Dr. Strand: Madeline, our group at UW was the first to provide clear evidence that plants attack TCE.

Rebecca: Is it possible for plants to be the ones to leave the toxic material in the soil?
Dr. Strand: Rebecca, not that I know of.

Rebekah: How many steps are in the process of phytoremedeation?
Dr. Strand: The number of steps in the phytoremediation of compounds like trichloroethylene is not known yet. That's one of the topics that we are studying. Trichloroethylene is a small molecule, so the number of steps is probably only about six or so. I have been studying bacteria and plants or about 25 years.

Sadie: Does TCE harm some plants too?
Dr. Strand: If you exposed them to enough TCE they are killed. This requires very high levels though, about 100 times more than you commonly find in polluted water.

Jordan: Wow, I didn't know there was a thing called a SMALL molecules.
Dr. Strand: Sure some molecules only have 4 atoms. TCE has 6 atoms. Big molecules, like DNA, have many thousands of atoms.

Christian: About how long would it take a plant to absorb and release a liter of TCE?
Dr. Strand: Christian, it will take me a while to calculate that answer. A liter of TCE is a lot compared to the amounts that are usually in groundwater pollution.

Jordan: How long have you been researching bacteria and plants
Dr. Strand: I was 30 when I started studying bacteria. I started with plants about 6 years ago.

Madeline: how can plants absorb toxic material? Can't it hurt them?
Dr. Strand: At low concentrations the plants aren't hurt by the toxic chemicals.

Jessica: How can plants suck in toxic chemicals? How does it work?
Dr. Strand: Plants take up toxic chemicals when they are dissolved in water around the roots. Many toxic chemicals just dissolve into the plant cells and are taken up that way. Metals are harder to get the plants to take up, but some plants do like to take up the metals, using special molecules (proteins) on the outside of their cells.

Jack: What category are Venus Flytraps in the plant kingdom?
Dr. Strand: Don't know about flytraps, Jack. There is a great collection of
carnivorous plants at the botany greenhouse at UW. It’s open to public.

Sadie: How old are you?
Dr. Strand: I am 57.

Jamie: Can plants absorb toxins in one season than in another?
Dr. Strand: There is more absorption of toxins when they are growing (during the summer).

ONeill: Class is over so we have to stop the chat now. Thanks for spending time with us.
Dr. Strand: Thank you. It was fun. Come down to the botany greenhouse and see the collection some time.