Although Ca oxalate is principally involved with the regulation of Ca in the plant16, it has been implicated in toxic metal compartmentalization17.
Gold toxicity is not confined to plants: recently, a biochemical mechanism for extracellular precipitation of Au by a bacterium was described20,21.
The findings from these field sites and laboratory experiments enable us to propose a tentative model for Au mobilization and precipitation for this biotic–abiotic system.
We assert that climatic and biological factors at Freddo, Barns and elsewhere are crucial for the transportation of Au to the surface from great depth.
The Eucalyptus trees are part of woodland at Freddo and at Barns stretching over several thousand square kilometres.
Despite these harsh climatic conditions, it is significant that the large trees at Freddo, in particular, are able to thrive.
The Eucalyptus root system is unusually deep and extensive22 with sinker roots in one species (Eucalyptus marginata) documented at 40 m depth23 (Fig. »