Phragmites partners with microbes to plot native plants' demise

Dec 23, 2009

University of Delaware researchers have uncovered a novel means of conquest employed by the common reed, Phragmites australis, which ranks as one of the world's most invasive plants.

The invasive strain, which hails from Eurasia, overtakes its "native" cousin, which has lived in North America for the past 10,000 years, ironically by provoking the native plant to "take itself out," through a combination of microbial and enzymatic activity in the .

The research by an interdisciplinary UD team led by Harsh Bais, assistant professor of plant and soil sciences, is reported in the December issue of the scientific journal Plant Physiology and also is highlighted in one of the journal's editorials.

Bais's co-authors include postdoctoral researchers Gurdeep Bains and Amutha Sampath Kumar in the Department of Plant and Soil Sciences in the College of Agriculture and Natural Resources; Thimmaraju Rudrappa, a former UD postdoctoral researcher who is now a research scientist at DuPont; Emily Alff, an undergraduate who became involved in the study through a Research Experiences for Undergraduates (REU) fellowship; and Thomas Hanson, associate professor of marine biosciences in the College of Earth, Ocean, and Environment.

In previous research, a team led by Bais determined that Phragmites employs a strategy known as allelopathy, in which plants release into the soil to deter other plants from growing close to them.

In soil studies at the Delaware Biotechnology Institute, a premier center for life sciences research at UD, the scientists discovered that invasive Phragmites produces elevated levels of a benign compound, a precursor of gallic acid known as gallotannin, relative to its native cousin.

However, when this gallotannin, a polymeric phenol, is attacked by tannase produced through by and rhizospheric microbes, toxic gallic acid is produced and released in the root zone, exacerbating the invasive Phragmites' noxiousness.

"The tannins are like partners in crime in the process," Bais said.

He noted that Hanson and Kumar collected microbes present on the root surface of the plants and revealed that the "bugs" cleave the polymer (gallotannin) to release the monomer (gallic acid) because the microbes are using the tannins as a carbon source.

"It's like a two-way highway," Bais said, "the plant is working with bacteria to secrete gallic acid into the soil."

Bais says that the microbial population is the same in the native versus the invasive Phragmites. The invasive variety simply secretes more gallotannins into the soil than its native cousin, putting the native plant at a disadvantage in turf battles between the two strains.

Phragmites has overtaken millions of acres of wetlands in the United States, thanks to the aggressive, invasive strain of the plant that came on the scene some 200 years ago from Eurasia.

The exotic species has displaced the non-aggressive native variety of the plant, relegating the native strain to isolated patches and wetland margins along the Atlantic coast.

"Now we have a way to remedy the sick soil," Bais said. "After years of research, we have identified a mechanism that may lead to a solution to the Phragmites invasion."

Explore further: Bear cub found dead in Spanish Pyrenees

add to favorites email to friend print save as pdf

Related Stories

Over time, an invasive plant loses its toxic edge

Sep 01, 2009

Like most invasive plants introduced to the U.S. from Europe and other places, garlic mustard first found it easy to dominate the natives. A new study indicates that eventually, however, its primary weapon ...

Recommended for you

Bear cub found dead in Spanish Pyrenees

4 hours ago

A brown bear cub that was part of an effort to reintroduce the species to the Pyrenees mountains has been found dead on the Spanish side of the mountain range, local officials said Monday.

Can stress management help save honeybees?

8 hours ago

Honeybee populations are clearly under stress—from the parasitic Varroa mite, insecticides, and a host of other factors—but it's been difficult to pinpoint any one of them as the root cause of devast ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.