Harvesting pollutants
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| Toxic metals can kill or stunt the growth
of the wild type of normal Arabidopsis plant. |
Phytoremediation is a far less destructive method
of environmental remediation than many traditional technologies.
“Up until now, the two basic methods of remediation were to
either to dig up the contaminated soil and haul it away to a hazardous
waste landfill or to leach that contamination out by applying chemicals
to the soil,” says David Salt, associate professor of horticulture
and director of the center. “Both methods are very expensive.
With the first option, you’re left with no soil, while the
other method leaves you with something that barely resembles soil.”
Instead, by harnessing the natural ability that some plants have
to take up metals, contamination can be removed while keeping the
soil in place—without the use of harsh chemicals that render
the soil unsuitable for future use.
Salt is internationally renowned for his work
with plants collectively known as “metal hyperaccumulators,”
which are capable of taking up and storing amounts of metals in
their shoots and leaves that would kill most other plants. Only
a handful of plants found in nature have this unique ability. Salt
not only studies how these plants hyperaccumulate metals but also
how to engineer other plants so that they may one day remove metal
contaminants from the soil as well.
Plants that naturally hyperaccumulate metals
are too small and grow too slowly to be useful in phytoremediation.
As Salt explains, “For phytoremediation to be successful,
you’ve got to think of it as farming—we’re farming
the metal out of the soil.” Like the ideal crop plant, the
ideal phytoremediation plant is one that grows quickly and develops
a sizeable amount of biomass, or living tissue, where the metal
is stored as the plant takes it up from the soil. Because scientists
haven’t found a hyperaccumulating plant in nature with those
characteristics, they are turning to biotechnology to help develop
one.
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| Arabidopsis that contains a gene from
a plant that naturally hyperaccumulates metals thrive. |
“We want to understand as much as we can at the molecular
level about how these natural accumulators work and then use that
information to genetically engineer plants that would be ideal for
phytoremediation,” he says. Ultimately, those plants could
be planted on polluted sites, grown for a season, then harvested
like any other crop plant—the difference being that these
plants would be full of metals that could later be extracted from
the leaves and stems and possibly even put to commercial use.
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