Science  25 Oct 2013:
Vol. 342, Issue 6157, pp. 408
  1. Money Does Grow on Trees

    Gold bush.

    Eucalyptus trees over a gold deposit had elevated calcium (shown) and gold, both drawn from the soil.


    Prospectors, take note: Trees growing over deeply buried deposits of gold ore sport leaves with higher-than-normal concentrations of the glittering element.

    Eucalyptus trees above a 35-meter-deep deposit in southern Australia had 20 times more gold in the gummy substances coating their leaves than did trees that grew 800 meters away, Mel Lintern, a geochemist at the CSIRO Earth Science and Resource Engineering division in Kensington, Australia, and colleagues report in this week's issue of Nature Communications.

    While previous studies have noted anomalously high gold concentrations, they couldn't rule out the possibility that tiny particles of the element had become stuck to leaves after being carried by wind. So Lintern's group also grew seedlings in laboratory greenhouses insulated from airborne dust, watering them with gold-tainted solutions to show that trees actually transport the element from soil into their leaves.

    The analysis provides "a conclusive set of evidence … from a very nicely constructed set of experiments," says Clifford Stanley, a geochemist at Acadia University in Wolfville, Canada. "The tree is a conveyor belt bringing gold to the surface."

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