Both humans and plants need iron in their diets, or else they get sick and don't grow. Humans can eat iron-rich foods or a supplement, but for plants, the process is more complicated, as iron in the soil has to be dissolved before the plant can absorb it.
With a one-year grant from Washington University's International Center for Advanced Renewable Energy & Sustainability (I-CARES), researchers at Washington University in St. Louis plan to use some high-tech methods to better understand the processes, mechanics and interfaces that plants use to move iron from the soil, through water and into the plant.
"Iron is hard to move from the soil into the plant because it has to dissolve in something, but it is notorious for its low solubility," says Daniel E. Giammar, PhD, the Harold D. Jolley Associate Professor of environmental & chemical engineering. "We are trying to determine how the iron gets from the soil mineral into the water by interacting with a range of compounds that we know plants release."
Giammar and Jeffrey G. Catalano, PhD, associate professor of earth & planetary sciences, both have expertise in aquatic systems — Giammar in aquatic chemistry, and Catalano in environmental geochemistry and mineralogy. The two Washington University investigators are combining forces with Stephan M. Kraemer, PhD, chair of geochemistry and head of the Department of Environmental Geosciences at the University of Vienna, and with Ivan Baxter, PhD, USDA research scientist at the Donald Danforth Plant Science Center. Kraemer will be at Washington University on sabbatical in early 2014.
The team will use a technique called scanning transmission X-ray microscopy (STXM) to measure the molecular changes in iron oxides by their reactions with natural compounds. STXM uses a high-powered X-ray beam focused to about 30 nanometers, providing the researchers with nanoscale maps of the elements and their oxidation states.
"STXM is a tool that uses the very bright focused X-rays and is only available at a few places in the United States," Giammar says. "With STXM, we can scan across the material and understand whether the iron is in an oxidized or reduced form, or whether it is more soluble. There may be some catalytic effects that make the whole iron pool more available."
Overall, the researchers seek to determine the mechanisms of how iron mobilizes when particular molecules and elements are in place, with the theory that they are working together to speed up key processes in which the plant dissolves and absorbs the iron.
As part of the grant funding, the team plans to hold a one-day Soil-Water-Plant Summit next spring to foster additional interactions between the university's research strengths in environmental chemistry and in plant science.
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