Medicines for the Earth: The Eco-Physiology of Plants
Phytoremediation: Using plants to heal the environment
Phytoremediation is the removal and degradation of contamination in soils and groundwater by plants. It utilizes a variety of plant physiological functions, including direct uptake of toxins, metabolism of those toxins into less toxic or nontoxic compounds, and degradative processes of bacteria and fungi within plant root systems. These processes, which are capable of removing low to moderate levels of environmental pollution, can be correlated with similar functions in the human body, which also degrade and eliminate xenobiotics and metabolic waste.
There are many advantages of using phytoremediation over conventional remediation methods: it is less expensive, it can be applied to a wide range of toxic metals and radionuclides, it is minimally disruptive to the environment, it is solar powered and energy efficient, it requires little maintenance, and it is aesthetically pleasing. There are thousands of phytoremediation projects in different stages of research and development around the world.
A wide range of environmental toxins can be remediated using plants. Phytoremediation is being used to clean up metals, pesticides, solvents, explosives, crude oil, polyaromatic hydrocarbons, and landfills. Hybrid poplar and Eastern cottonwood remove chlorinated solvents in ground water. Petroleum and its hydrocarbons can be removed from soil and ground water using alfalfa, poplar and juniper, fescue grass, crabgrass, and clover. Polyaromatic hydrocarbons are remediated with ryegrass and mulberry trees. Heavy metals can be removed from soil using poplar and pine trees, chaparral, various grasses, and castor plants. Radionuclides can be removed from ground water with sunflowers and water hyacinth, and from the soil with mustards and cabbage. Explosives such as TNT can be removed from groundwater with duckweed and parrot feather grass. Nitrates can be remediated with cottonwood and poplar trees. Various water plants, including hyacinths, are being used in municipal sewage treatment.
In the last five years it has become clear that while phytoremediation has significant benefits in certain applications, its widespread commercial use is limited by the natural processes of plant physiology: plants degrade toxins slowly, large areas are needed for planting, many plants cannot be grown in the soils and climates where they are needed, and much remains unknown about the field in general. The scientific community involved in this research is now exploring genetic modification of plant physiology as a way of enhancing their remediating powers.
Some improvements in plant remediation capacity using genetic modification have been reported, such as using bacterial genes to help plants degrade mercury more efficiently. By inserting mammalian genes to express cytochrome P450 liver enzymes, plants have been modified to enhance their degradation of trichloroethylene, a ubiquitous toxic solvent used in dry cleaning.
It is ironic that scientific advances intended for human betterment are the original source of the chemical, biological, and nuclear waste that now needs remediating. It seems likely that the well-intentioned efforts to improve plant functions with genetic modification, like much of modern allopathic medicine, may yield symptomatic benefits while worsening the overall health of the biosphere. Holistic medicine, on the other hand, addresses the causative factors of illness and works to eliminate them. The obvious solutions to widespread contamination of the earth is to first stop manufacturing and using toxic substances (detoxifying the patient from addictions), converting to nontoxic plant-based alternatives (creating a healthy lifestyle), and enhancing phytoremediation capacities by restoring ecosystems to their original biodiversity (restoring systemic immunity and homeostasis).