Einstein Science Reporting for Kids
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American Association for the Advancement of Science

Parasite plants 'sniff' out their new homes

"Witches' shoelaces," "hairweed," "devils hair," "devilguts": these are all nicknames for the dodder plant, which winds around other plants and sucks out nutrients and water. Large numbers of dodder plants looks like a big tangle of hair smothering their host plants.

You can probably guess how most of these nicknames came about, though we're still scratching our heads over "devilguts."

Dodder plants are parasites. They don't have leaves, so most of the time they're basically just stems, winding their way around their host plants. They get all their nutrition from these hosts.

Once they sprout from their seeds, dodder plants only have a few days to live before they must find a host plant to attach to. How do they find their new homes?

A new study suggests that they can sense the "aromas" that host plants give off. Hosts such as the tomato plant emit a variety of compounds into the air. Justin Runyon and his colleagues at Pennsylvania State University found that dodder seedlings detect these compounds and grow toward their source.

The seedlings also seem to be able to distinguish the "smell" of host plants that they prefer, such as the tomato plants, from host plants they only choose if they have to, such as wheat plants.

Obviously plants don't have noses, which are what animals use to detect airborne compounds like these. Scientists still need to do more research to learn exactly how plants detect these chemical cues.

Dodder is on the U.S. Department of Agriculture's Top Ten Weeds List, and researchers and farmers would like to find ways to prevent the plant from harming their crops. Dr. Runyon and his colleagues hope that their discovery might help these efforts. Their findings appear in the 29 September issue of the journal Science.