[APWG] Re: [ma-eppc] RE: Killer plant- spotted knapweed poisons rivals- article NYTim es
Sue_Salmons at nps.gov
Sue_Salmons at nps.gov
Tue Sep 9 13:11:53 CDT 2003
I was making the same conjecture, seeing as we can easily kill the
microstegium before it sets seed, but it seems to come back rather than
leaving room for natives to come return.
Sue Salmons
Resource Management Specialist - Vegetation
Rock Creek Park
202-895-6077
"Michels,
Kathleen To: "'MALawler at aol.com'" <MALawler at aol.com>,
(NIH/FIC)" ma-eppc at yahoogroups.com, apwg at lists.plantconservation.org
<michelsk at ficod.f cc:
ic.nih.gov> Subject: [ma-eppc] RE: Killer plant- spotted knapweed
poisons rivals- article NYTim es
09/09/2003 01:36
PM AST
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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