A rock-iron-solubilizing compound from root exudates of Tephrosia purpurea

Root exudates from Tephrosia plants contained a rock-iron [Fe(OH)(3)]-solub ilizing compound. This was purified to apparent homogeneity and appears to possess an iron-binding phenolic moiety linked to a proteinaceous component that may act as a receptor. The lyophilized purified fraction showed maxim um Fe(OH)(3)-solubilizing activity at 50 degrees C under acidic pH. Its act ivity was influenced by trace ions (Co, Cu, Zn, B, Mo, Mn) and toxic metal ions (Ni, Al, Pb, Cr, Hg), but ions such as Na, K, Mg, and Ca had no signif icant effects on its Fe(OH)(3)-solubilizing activity.