Featured Research

from universities, journals, and other organizations

Parasitic Plants Sniff Out Hosts

Date:
September 30, 2006
Source:
Penn State
Summary:
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.

Tomato seedling stem with dodder.
Credit: Photo Consuelo De Moraes & Mark Mescher, Penn State

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.

Related Articles


"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 assumed that the search was random and the location of a host simply a chance encounter. After four days, when the plant was growing flat on the filter paper, the researchers measured the direction of the shoot.

The researchers report that 80 percent of the dodder plants grew onto the side of the filter paper nearest the tomato, with many growing directly towards the tomato plant. Statistical analysis provided strong evidence for directed growth by dodder, but did not indicate what causes the directionality.

The Penn State researchers then challenged dodder seedlings with artificial tomato plants, pots of moist dirt, and vials of green or red water. None of these objects elicited any directional growth. Then, to narrow down the possible cues being used, they tested the seedlings' response to tomato plants slightly separated from the dodder seedlings, out of view so to speak, in a set-up designed to block possible light cues. The researchers observed a growth response toward the tomato plants similar to that in their first experiment. Finally, to firmly establish that volatile chemicals from the host plant were causing this response, the researchers used the same set-up to examine the response to extracted host volatiles, using a solvent-only sample as a control in the opposite direction. They again observed a strong growth response toward the tomato volatiles.

"This showed that host volatiles elicit a growth response in the absence of any other plant-derived clues," says Mescher. "However, while volatile chemicals might be key, our results do not rule out the possibility that other cues such as light or shade may play a role."

After establishing the role of volatiles in leading the parasite plants to their tomato hosts, the researchers looked at other potential hosts including wild impatiens, and showed that the parasites were attracted to a wide variety of plants. They even found attraction to wheat plants, a poor host on which the dodder seedlings do not survive. However, when the researchers offered the seedlings a choice between wheat and tomato plants, the tomato won out, indicating that the parasites have some way of deciding between a good host and a bad host.

The researchers examined responses to some of the individual compounds released by host plants. Of seven compounds tested from tomato, three caused a directional growth response in dodder. One of these chemicals is also released by wheat, which might explain why wheat is somewhat attractive despite being a poor host. However, another chemical compound from wheat actually repels the dodder seedlings, perhaps explaining why the odor of wheat is less attractive than that of the preferred host tomato..

The Penn Stsate researchers note that the identification of at least one repellent compound raises the possibility of eventually using airborne chemicals to deter plant parasites. Looking forward, they would also like to determine exactly how the parasites are able to sense and respond to host volatiles. They hope to identify the specific chemical receptors involved. They are also examining the defensive mechanisms by which host plants respond to attack by parasitic plants.


Story Source:

The above story is based on materials provided by Penn State. Note: Materials may be edited for content and length.


Cite This Page:

Penn State. "Parasitic Plants Sniff Out Hosts." ScienceDaily. ScienceDaily, 30 September 2006. <www.sciencedaily.com/releases/2006/09/060929094158.htm>.
Penn State. (2006, September 30). Parasitic Plants Sniff Out Hosts. ScienceDaily. Retrieved December 18, 2014 from www.sciencedaily.com/releases/2006/09/060929094158.htm
Penn State. "Parasitic Plants Sniff Out Hosts." ScienceDaily. www.sciencedaily.com/releases/2006/09/060929094158.htm (accessed December 18, 2014).

Share This


More From ScienceDaily



More Plants & Animals News

Thursday, December 18, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

When You Lose Weight, This Is Where The Fat Goes

When You Lose Weight, This Is Where The Fat Goes

Newsy (Dec. 17, 2014) Can fat disappear into thin air? New research finds that during weight loss, over 80 percent of a person's fat molecules escape through the lungs. Video provided by Newsy
Powered by NewsLook.com
The Hottest Food Trends for 2015

The Hottest Food Trends for 2015

Buzz60 (Dec. 17, 2014) Urbanspoon predicts whicg food trends will dominate the culinary scene in 2015. Mara Montalbano (@maramontalbano) has the story. Video provided by Buzz60
Powered by NewsLook.com
Rover Finds More Clues About Possible Life On Mars

Rover Finds More Clues About Possible Life On Mars

Newsy (Dec. 17, 2014) NASA's Curiosity rover detected methane on Mars and organic compounds on the surface, but it doesn't quite prove there was life ... yet. Video provided by Newsy
Powered by NewsLook.com
Ivory Trade Boom Swamps Law Efforts

Ivory Trade Boom Swamps Law Efforts

Reuters - Business Video Online (Dec. 17, 2014) Demand for ivory has claimed the lives of tens of thousands of African elephants and now a conservation report says the illegal trade is overwhelming efforts to enforce the law. Amy Pollock reports. Video provided by Reuters
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins