Some flowers release a pleasing fragrance. Other plants smell. And then there's the parasitic dodder vine, which has the remarkable ability to sniff out its victims.
Farmers have placed the dodder - aka "Strangleweed," "Devil Guts," and "Witches Shoelaces" - on a ten most-wanted list of weeds.
Swarthmore College biology professor Colin Purrington says the vine starts out as just a tiny tendril with no roots or leaves. It then has about a week to find a host plant it can wrap itself around. The vampire-like dodder then sinks its fangs into its victim and starts drinking.
"It's probably one of the creepiest plants I know," says Purrington. "It's a horrible existence for the host plant. If plants could scream, they'd have the loudest screams when they had dodder attached."
Researchers didn't know how the dodder attached to its host victims. They speculated that the vine might be attracted to water vapor or the refractive light off a potential host.
But three researchers at Pennsylvania State University discovered that the dodder follows the scent of its victims.
Plant biologist Consuelo M. De Moraes says when they wafted odors in the direction of a dodder seedling, the tendril almost always began to creep toward the smell.
"It's really amazing to watch this plant having this almost animal-like behavior," she says. "It's really very sophisticated and surprising."
The study showed dodder also prefers certain odors. Given a choice of tomato or wheat, the dodder picks the tomato. Wheat may give off a chemical that repels the vines, which could mean good news for farmers.
"The fact that there are these repellant compounds suggest that you might be able to create a repellant or deterrent effect that would allow you to protect a crop against infestation," says Mark Mesker, a researcher at Penn State.
Details of the dodder's olfactory talents appear in the current issue of the journal Science.