Colorado State University Identifies Natural, Plant-Produced
Scientist: Jorge M. Vivanco, Horticulture & Landscape
Arch Dept, 970-491-7170, Jorge.Vivanco@ColoState.EDU;
Source: Dell Rae Moellenberg, 970-491-6009, Colorado State AgNews
Scientists have speculated for decades that spotted knapweed
is able to spread over large areas because of a secret weapon
- an ability to release a chemical that kills surrounding plants.
Until now, they have never been able to put their thumb on the
phenomenon, but recently a Colorado State University horticulture
professor identified and isolated the chemical for the first time.
What’s more, they are using the chemical as a completely
natural and environmentally friendly herbicide to kill other weeds.
The discovery and isolation of the chemical, called catechin,
within spotted knapweed may revolutionize the war against weeds
for homeowners and farmers. For years, scientists have talked
about spotted knapweed releasing this chemical, but they couldn’t
find it in the soil because it was almost impossible to separate
from all the other compounds that naturally occur in soil, said
Jorge Vivanco, assistant professor of horticultural biotechnology
at Colorado State. We looked for it in the plant. Spotted knapweed
releases catechin into the soil through its roots.
Now that catechin has been identified and isolated, and scientists
can capture the chemical in the Department of Horticulture’s
laboratory, Vivanco and a team of researchers at Colorado State
are investigating a wealth of applications for the chemical. They
have discovered that the weed produces two types of catechin that
are the same chemical compound but the mirror image of each other
in their structure. One has anti-bacterial properties and the
other acts as a natural herbicide.
The chemical acts as a natural herbicide to most other plants,
although grasses and grassy-like plants, such as wheat, display
some resistance to it. This discovery alone holds much potential.
For example, it may mean that specific amounts of catechin could
be used on lawns to kill weeds without killing grass or on wheat
without damaging the crop. The chemical also is environmentally
friendly and has existed in the soil for decades.
Catechin kills other species of knapweed, such as diffuse knapweed,
which also is a noxious weed. It is fatal to spotted knapweed
only when manually inserted into its cells in a laboratory. In
nature, spotted knapweed cells do not permit catechin to reenter
the plant once the chemical is produced and released into the
soil. It is a clever root to produce, secrete and protect itself
from this chemical, Vivanco said. There are only small amounts
of catechin inside a root at any given time; it secretes it as
it produces it.
The Colorado State team has found that spraying catechin on
plants or adding it to soil is as effective as 2,4-D against pigweed,
lambs quarters and other common weeds. Catechin usually kills
cells within the plants in an hour and kills the plants in about
a week, but the team still is investigating the length of time
that it remains active in the soil to prohibit plant growth. The
researchers are working with commercial companies to make spotted
knapweed catechin spray available to consumers within a year or
two. Colorado State researchers also are working to transfer the
genes that produce the natural chemical into other plants to give
them a built-in defense mechanism against weeds.
Perhaps one of the most promising applications of the discovery
is the fact that spotted knapweed has such a complex defense mechanism.
Spotted knapweed immediately begins to produce and release chemicals
at the slightest hint of a threat or stress. Just tapping its
leaves automatically activates the plant’s chemical response.
The funding for these projects comes from Colorado State University’s
Invasive Weeds Initiative.
Plants' Odors Can Help Farmers Keep Them Healthy
Scientist: Dr. Glen Rains, Ext. Engineer, Biological &
Agricultural Engineering, University of Georgia, 229-386-3377.
Source: Brad Haire, Editor, College of Agricultural and Environmental
Plants respond to stresses like drought, disease and insect
attacks in many ways. But one unusual way could lead to new tools
that can help farmers precisely monitor and react to what's happening
in their fields before a problem gets out of hand. Plants can
tell you what is happening to them, says Glen Rains, an engineer
with the University of Georgia College of Agricultural and Environmental
Sciences. You just have to figure out how to understand what they
are trying to say.
"Plants do a lot just sitting there," Rains said.
Sometimes it's easy to read what a plant says. But sometimes it's
hard. It's hard to know, for instance, if a plant has a disease
attacking it underground. You may not know until the damage is
done. Some underground peanut and cotton diseases and the damages
they cause can go unnoticed right up until harvest time. Then
it's usually too late to do anything about it. But if you know
how to do it and have a sensitive enough instrument, Rains says,
you could smell a plant and find out a lot more about it.
Scientists at the Coastal Plains Experiment Station here and
at U.S. Dept. of Agriculture in Florida have already proven that
when attacked by caterpillars, plants release a chemical odor
that attracts parasitic wasps to the attacked plant. The wasp
then implants an egg into the attacking caterpillar. The egg hatches,
and the larva eats the worm. In fact, different wasps prefer certain
kinds of caterpillars. The plant releases a different chemical
odor depending on the caterpillar attacking it.
"The question of whether plants evolved to release odors
that attracted insects, or whether the insects evolved to respond
to chemicals produced by the plants is not answered," Rains
said. "It's probably a combination of both." Rains is
taking this research further. If plants release chemical odors
during a worm attack, could they also release chemical odors during
a disease attack? Well, they do. In defense, plants under a disease
attack produce chemicals. "We're not detecting signals as
much as we are detecting by-products of direct plant defense against
the pathogen attack," Rains said.
Aspergillus is a fungus that attacks peanuts underground. The
fungus causes aflatoxin, which in certain levels can be harmful
to humans. But it's very hard to know where the aflatoxin is in
a field. Peanuts are tested for this fungus after harvest. Small
samples are tested. If the fungus is found, a whole shipment of
peanuts could be segregated. This costs the farmer money at market.
Knowing where the aflatoxin is in a field would help peanut farmers
more efficiently treat the problem, said John Beasley, UGA CAES
agronomist. It would also help come harvest time. "It would
be tremendously important to a farmer," he said, "to
be able to isolate a field or an area of the field where aflatoxin
is developing and avoid harvesting with the rest of the peanuts."
Rains hopes to create a catalog of the different odors plants
produce when attacked by insects or diseases, or when the plant
needs nutrients or water. Rains envisions a device a farmer or
farm worker would carry and place over plants in a field. The
device could "smell" the odors released from the plants,
and then reads more accurately what the plant is trying to say
about its condition.