[APWG] RE: Killer plant- spotted knapweed poisons rivals- article NYTim es

Tue Sep 9 12:36:50 CDT 2003

I'd be willing to  bet Japanese Stiltgrass does this too. I've had a an
impossible time getting regrowth of natives in test areas where I've
eliminated Stiltgrass for years. Even vigourous reseeders like Jewelweed
aren't coming back. 
> -----Original Message-----
> From:	MALawler at aol.com [SMTP:MALawler at aol.com]
> Sent:	Tuesday, September 09, 2003 1:22 PM
> To:	ma-eppc at yahoogroups.com; apwg at lists.plantconservation.org
> Subject:	Killer plant- spotted knapweed poisons rivals-  article
> NYTimes
> 
> 
> September 9, 2003
> 
> 
> Forensic Botanists Find the Lethal Weapon of a Killer Weed
> 
> By CAROL KAESUK YOON
> 
> 
> 	
> 
>  <http://graphics7.nytimes.com/images/dropcap/f.gif>or over a century,
> spotted knapweed has been a growing scourge on the North American
> landscape, spreading across millions of acres of prairies, hillsides,
> roadsides and rangeland - pretty much anywhere it can get a root in the
> dirt. Everywhere it spreads, it replaces native grasses and other plant
> species to the consternation of conservationists as well as ranchers,
> whose cows refuse to eat it. 
> 
> The weed, which sprouts pink and purple flowers and can grow a spindly
> three feet tall, is a European import, thought to have been introduced in
> North America as a contaminant in crop seeds or in dirt used as ship's
> ballast and then dumped. But scientists have long been baffled by the
> plant's appalling effectiveness at driving out other plants.
> 
> Now in the current issue of the journal Science, researchers say they have
> found spotted knapweed's deadly secret: a potent and previously unknown
> poison that it releases through its roots into the soil to kill off
> neighboring plants. By eliminating its neighbors, the weed can appropriate
> all the water and nutrients that the other plants would have taken, and it
> has plenty of new space to spread out in. 
> 
> Dr. Jorge M. Vivanco, a plant biologist at Colorado State University and
> an author of the study, says the toxin acts so quickly that within 10
> seconds of contact the neighboring plants' roots begin producing chemicals
> that set off a cascade of events that will ultimately kill their own
> cells.
> 
> "In one hour the roots die," he said. "The whole plant dies in a matter of
> days." The substance is such an effective herbicide that, Dr. Vivanco
> said, his university had already taken out a patent on it.
> 
> Scientists often assume that invasive exotic species are able to thrive in
> new environments because they have escaped from their predators and other
> enemies at home. But scientists say the new study suggests that such
> troublesome imports may also succeed by using potent but unrecognized
> methods, like chemical warfare.
> 
> "This is a really nice demonstration that other factors come into play,"
> said Dr. Sarah Reichard, an invasion biologist at the University of
> Washington. "This paper shows that the interactions can be very subtle,
> things happening below ground that we really haven't had any knowledge
> about." 
> 
> The notion that plants use poisons to suppress or kill their neighbors - a
> phenomenon known as allelopathy - has been around for decades. But until
> now, few scientists have had much use for it.
> 
> "People have been rather dismissive of the whole subject," said Dr.
> Alastair Fitter, an ecologist at the University of York who was not
> involved in the study.
> 
> Part of the problem was that much of the earliest work was poorly done, he
> said in a telephone interview. But as Dr. Fitter wrote in an accompanying
> commentary in Science, he believes the new study is so convincing that it
> will "now place allelopathy firmly back on center stage." 
> 
> The researchers found that the roots of the spotted knapweed released two
> forms of a chemical known as catechin (pronounced KAT-uh-kin) identical in
> all respects except that their molecular structures were mirror images of
> each other. 
> 
> One form, known as +catechin, is also found in green tea and was already
> known as an antioxidant, able to neutralize the harmful molecules called
> reactive oxygen species that are thought to speed the aging process.
> 
> The toxin turned out to be the second form, -catechin, which had
> essentially the opposite effect of its mirror image. It induced the
> production of harmful reactive oxygen species in neighboring plant roots,
> setting off the process that led to cell death.
> 
> The finding helps explain the failure of many efforts to fight the
> onslaught of spotted knapweed by burning it and then seeding the area with
> desired plants.
> 
> "What they've seen is that 99 percent of the seeds died, and now we know
> why," said Dr. Vivanco. With -catechin soaked into the soil, he said,
> susceptible seeds have no chance of making it.
> 
> But even though the poison is very powerful, it remained unknown to
> researchers because everything was happening below ground.
> 
> "One plant arrives in a field where there are a lot of native plants," Dr.
> Vivanco said. "The next year you see not one, but actually a patch of
> spotted knapweed where the natives were. And if there are still native
> plants near it, they don't look so healthy." 
> 
> Around Missoula, Mont., home of the University of Montana, for example, a
> diversity of native species once bloomed.
> 
> Now after several decades of this subtle underground warfare, the hills
> have become a vast monoculture of spotted knapweed, Dr. Vivanco said, as
> have millions of acres in that particularly hard-hit state.
> 
> The scientists found that the grasses that grow alongside spotted knapweed
> in Europe are much better able to resist its toxins than native North
> American grasses. Scientists say this suggests that the European grasses
> have evolved a resistance to this potent toxin, one that North American
> grasses lack.
> 
> Since spotted knapweed landed in North America, a century or so ago, it
> has spread to nearly every state and has caused a variety of problems. 
> 
> Eric Lane, the state weed coordinator for Colorado, said the loss of
> native plant species curtailed the food supply not only for cattle but for
> wild species like elk, many birds and insects. In some states, he said,
> the spread of spotted knapweed is so severe that elk herds have altered
> migration pathways to avoid vast inedible swaths of it.
> 
> The weed has also led to erosion because it does not hold soil as well as
> native grasses.
> 
> In the search for solutions to this green plague, researchers were excited
> to discover that the plant Arabidopsis thaliana, whose entire genome has
> already been sequenced, is susceptible to -catechin. As a result, they can
> see in detail how a plant's genome reacts when its roots are hit with the
> toxin.
> 
> The scientists found 10 genes that appear to shift into high gear
> immediately. Scientists say they hope that by identifying what those genes
> are doing, presumably mounting the beginnings of a defense, they can
> genetically engineer plants that can more effectively resist the spotted
> knapweed's attacks.
> 
> Researchers are also testing to see what native plants are resistant to
> the -catechin. They hope to develop a list of species that can be used to
> revegetate an area after spotted knapweed has been burned.
> 
> So far, the researchers have found no native plants that can withstand the
> poison.
> 
> 
> Copyright 2003
> <http://www.nytimes.com/ref/membercenter/help/copyright.html>  The New
> York Times Company <http://www.nytco.com/>
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