Parasitic plants do not haphazardly flail about looking for a host but sense volatile chemicals produced by other plants and identify potential hosts by their emissions, according to a team of Penn State chemical ecologists.

"We are interested in how plants respond to their environment, and have looked at plant insect interactions," says Dr. Consuelo M. De Moraes, assistant professor of entomology. "It was surprising to see how little was available on how above-ground parasitic plants find their hosts from far-off."

The researchers looked at Cuscuta pentagona, field dodder or five angle dodder, a plant that infests a variety of crops including tomatoes, carrots, onions, citrus trees, cranberries and alfalfa and reported their finding in today's (Sept. 29) issue of Science. Dodder grows throughout the world and is a difficult pest to eliminate because chemicals that kill the parasite also often kill the host plant.

"There is currently no reliable way to get rid of these pests," says Justin B. Runyon, graduate student in entomology. "It is estimated that in California each year, a 20 percent infestation of the tomato crop reduces yield by 25 percent and causes a loss of 4 million dollars."

The researchers used a variety of experiments to determine how newly emerging dodder shoots find a host. The length of time these parasites can live without a host is determined by the amount of food stored in the seed, but they can only grow about four inches before they die.

"These plants have no roots and barely have leaves and the flowers are very tiny," says Mark C. Mescher, assistant professor of entomology.

First the researchers placed dodder seedlings in a water vial at the center of a filter paper disk. A tomato plant was placed near the edge of the disk and the dodder plant was allowed to grow and attempt to locate its host. Dodder plants search for hosts by growing and moving in a circular pattern. In the past, many assu
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Contact: A'ndrea Elyse Messer
aem1@psu.edu
814-865-9481
Penn State
28-Sep-2006