Phytate exudation by the roots of Pteris vittata can dissolve colloidal FePO4
2022
Khan, Sangar | Milham, Paul J. | Eltohamy, Kamel Mohamed | Jin, Yingbing | Wang, Ziwan | Liang, Xinqiang
Phosphorus (P) is limiting nutrient in many soils, and P availability may often depend on iron (Fe) speciation. Colloidal iron phosphate (FePO₄cₒₗₗ) is potentially present in soils, and we tested the hypothesis that phytate exudation by Pteris vittata might dissolve FePO₄cₒₗₗ by growing the plant in nutrient solution to which FePO₄cₒₗₗ was added. The omission of P and Fe increased phytate exudation by P. vittata from 434 to 2136 mg kg⁻¹ as the FePO₄cₒₗₗ concentration increased from 0 to 300 mM. The total P in P. vittata tissue increased from 2880 to 8280 mg kg⁻¹, and the corresponding increases in the trichloroacetic acid (TCA) extractable P fractions were inorganic P (860–5100 mg kg⁻¹), soluble organic P (250–870 mg kg⁻¹), and insoluble organic P (160–2030 mg kg⁻¹). That is, FePO₄-solubilizing activity was positive correlated with TP, TCA P fractions in P. vittata, TP in growth media, and root exudates. This study shows that phytate exudation dissolved FePO₄cₒₗₗ due to the chelation effect of phytic acid on Fe; however, the wider question of whether phytic acid excretion was prompted by deprivation of P, Fe, or both remains to be answered.
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