Pollution Fighting Plants

Additional Information

Bibliography

- Mosses are being modified to serve as bio-indicators for pollution levels in the air.

- Poplars are also being modified to produce more ethanol as an alternative fuel source. The ethanol is derived from cellulose in the plant cells, which helps to give the plant structure.

- Japanese researchers published findings in 2005 about using a human gene to make rice plants degrade a variety of herbicides, something they said could help reduce the load of herbicides in paddy fields and streams.

Works Cited

"Fighting Pollution the Poplar Way: Trees to Clean up Indiana Site." Fighting Pollution the Poplar Way: Trees to Clean up Indiana Site. N.p., n.d. Web. 01 May 2014.

"Fighting Pollution the Poplar Way: Trees to Clean up Indiana Site." Fighting Pollution the Poplar Way: Trees to Clean up Indiana Site. N.p., n.d. Web. 01 May 2014.

"Genetically Engineered Poplar Plants Disarm Toxic Pollutants 100 Times Better Than Controls." ScienceDaily. ScienceDaily, n.d. Web. 01 May 2014.

"Innovative Technologies Join the Superfund Cleanupof Ground Water at Fort Lewis, Washington." USGS: Superfund Cleanup of Ground Water, Ft. Lewis, Washington. N.p., n.d. Web. 01 May 2014.

"Pollution-fighting Poplar Trees." Biology Fortified Inc. N.p., n.d. Web. 01 May 2014.

"Trichloroethylene." Wikipedia. Wikimedia Foundation, 05 July 2014. Web. 01 May 2014.

Presentation created by

Lucy Xu

Biotechnology Honors

2014

Current Uses

Safety Issues

Currently, the pollution-fighting poplars are not in use anywhere within the United States or the world, other than in an experimental setting. A 2008 article stated that Purdue University researchers are collaborating with Chrysler LLC in a project to use poplar trees to eliminate pollutants from a contaminated site in north-central Indiana.

Pollution Fighting Plants

The main safety issue is that the transgenes will spread to other poplar plants in the area, if planted. Additionally, there are concerns that the transgenes could negatively impact animals in the environment such as bugs who chew on plant tissues.

Legal/Political Issues

Commercial use of these trees requires federal regulatory approval and monitoring, and regulations are becoming increasingly strict for transgenic plants intended for biopharmaceutical or industrial purposes, including phytoremediation.

Pros

This method of pollution removal is less expensive than most other methods, and in addition, it is potentially the least harmful method because it uses naturally occurring organisms and preserves the environment in a more natural state.

One benefit of using poplar trees over other plants is that they grow in a wide variety of climates. Another benefit is that they take five years to reach sexual maturity. As long as the trees are harvested before they start producing pollen, the transgenes can not spread to native poplars.

Additionally, this allows researchers to easily monitor the poplars and control where they are planted and what effects they will have on the environment.

Cons

Some fear that the transgenes may have the potential to spread to other plants in the area and disrupt the ecosystem.

Bioaccumulation of toxic materials could impact other members of the food chain.

Additionally, plants take years to grow, and have a relatively low biomass while they are still reaching maturity, so this project would require a long-term commitment.

The survival of the plants is also influenced by the toxicity of the environment and the general quality of the soil, so in some sites the trees may not be able to be planted.

How are the poplars genetically modified?

Background Information

Both unaltered poplars and the transgenic poplar plants produce the enzymes to break down trichloroethylene, C2HCl3, into chloride ions -- harmless salt that the plant sheds -- and recombines the carbon and hydrogen with oxygen to produce water and carbon dioxide.

The transgenic poplar plants just do it a lot faster. The enzymes used to metabolize the contaminants are from a group called cytochrome P450 found in both plants and animals. Poplars have a lot of P450s and researcher Sharon Doty from the University of Washington said scientists hope to eventually sort them to find ways to manipulate the plant's own genes to promote pollution degradation. In the meantime they are conducting experiments inserting a gene that produces the protein cytochrome P450 in mammalian livers, in this case the livers of rabbit, into the poplar genomes. Poplar genes producing cytochrome P450 is expressed in all their cells, but not at the rates achieved by the transgenics.The trees were engineered to over-express the cytochrome P450, and afterwards, the transgenic trees were able to remove 91% of trichloroethylene from a liquid solution, compared to just 3% removed by untransformed poplars.

The Pollution Problem

Trichloroethylene, a carbon-based chlorinated volatile organic compound (VOC), is the most common groundwater contaminant at U.S. Superfund sites. A Superfund site is an uncontrolled or abandoned place where hazardous waste is located, possibly affecting local ecosystems or people, as designated by the United States Environmental Protection Agency (USEPA). Additionally, though plants produce VOCs when they decay, but a major source comes from automobile exhaust, coal burning, and other human activities. Some atmospheric VOCs combine with oxygen to form tiny airborne particles called oxygenated VOCs (oVOCs), which insulate the atmosphere and lead to warming.

What is phytoremediation?

Phytoremediation describes the treatment of environmental problems (bioremediation) through the use of plants that mitigate the environmental problem without the need to excavate the contaminant material and dispose of it elsewhere.

Phytoremediation consists of mitigating pollutant concentrations in contaminated soils, water, or air, with plants able to contain, degrade, or eliminate metals, pesticides, solvents, explosives, crude oil and its derivatives, and various other contaminants from the media that contain them.

One process of phytoremediation, phytoextraction (or phytoaccumulation) uses plants or algae to remove contaminants from soils, sediments or water into harvestable plant biomass (organisms that take larger-than-normal amounts of contaminants from the soil are called hyperaccumulators). The plants absorb contaminants through the root system and store them in the root biomass and/or transport them up into the stems and/or leaves. A living plant may continue to absorb contaminants until it is harvested. After harvest, a lower level of the contaminant will remain in the soil, so the growth/harvest cycle must usually be repeated through several crops to achieve a significant cleanup. After the process, the cleaned soil can support other vegetation.