The University Record, March 19, 1996

U-M-Dearborn researchers try breeding
'metal-consuming plants'

By Terry Gallagher

In urban areas like Detroit, vacant plots of land that are currently useless because the soil is polluted "could be turned into lush gardens of metal-consuming plants, trees and shrubs," if two scientists at the U-M-Dearborn have thei r way.

Kent Murray and John C. Thomas, assistant professors of natural sciences, are working to develop plants th at take up large amounts of toxic metals from the soil into their leaves, which could then be burned or composted to recycle the metals.

"By breeding and planting metal-accumulating plants at hazardous waste sites, we should be able to cleanse urban areas of toxic levels of zinc, nickel, copper and lead," according to Murray and Thomas.

Murray is a geologist specializing in environmental geology and geochemistry, and Thomas is a plant molecular and cellular biologist. They are collaborating on several projects connected to "phytoremediation," or the use of plants to re move pollutants from the environment.

"We believe that phytoremediation could provide a cost-effective alternative to digging up and hauling contaminated soil to a hazardous-waste landfill," they wrote in a summary of their work.

All plants take up some metals from the soil as they grow. Generally, one-third of the metals that are absorbed are transported from the roots to the shoots and leaves. Using molecular gene transfer methods, Murray and Thomas are working to deve lop plants that are better able to accumulate large amounts of specific metals in their leaves, compared to existing species.

Polluted soil resulting from decades of industrial activity is one of the major obstacles to redeveloping many urban areas in America. According to some reports, treating soils contaminated with metals will cost more than $7 billion in the United States in the next five years. Another $35 billion will be spent on treating soils contaminated with metals mixed with organic contaminants.

Phytoremediation is in the experimental stage and to this point plants capable of taking up large amounts of metal have only been grown under laboratory conditions. "While the results of these experiments are promising, growing plants in soi l at a toxic site is quite different from growing plants in a controlled laboratory experiment," Murray and Thomas note.

Murray's research focuses on how metals in soil are tied up in insoluble forms that make the metals less available to the plants. Thomas and other researchers recently have established that metal-induced responses in plants are linked to some str ess- and wound-response pathways.

"Identifying and understanding how specific genes are regulated in metal-accumulating plants may provide clues for designing and engineering plants with enhanced metal tolerance and promoting phytoremediation using traditional plant breeding and transgenic approaches," the researchers note.

Murray and Thomas have been conducting some experiments and cultivating plants in a two-acre greenhouse in Belleville, built over the landfill operated by Environmental Quality, Inc. The greenhouse is heated by methane gas generated by the decomp osition process in the landfill.