Organic anions facilitate the mobilization of soil organic phosphorus and its subsequent lability to phosphatases

• Published in: Plant and soil Vol. 476; no. 1-2; pp. 161 - 180
• Main Authors: Richardson, Alan E., George, Timothy S., Hens, Maarten, Delhaize, Emmanuel, Ryan, Peter R., Simpson, Richard J., Hocking, Peter J.
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01.07.2022; Springer; Springer Nature B.V
• Subjects: Agriculture; Anions; Bioavailability; Biomedical and Life Sciences; citrates; Ecology; Ecosystem management; Environmental aspects; Enzymes; Hydrolysis; Inositol; Inositols; Ions; Lability; Life Sciences; Magnetic resonance spectroscopy; malates; Material requirements planning; Microorganisms; Molybdate; NMR; NMR spectroscopy; Nuclear magnetic resonance; Nucleic acids; Organic phosphorus; oxalates; Oxalic acid; Phosphatase; Phosphatases; Phosphodiesterase; Phospholipids; Phosphorus; Phosphorus in the body; Phytase; phytases; Plant Physiology; Plant roots; Plant Sciences; Research Article; Soil dynamics; soil organic phosphorus; Soil Science & Conservation; Soil types; Soils; spectroscopy; Australia; NMR; Malate; Plant nutrition; Oxalate; Phytate; Citrate; Phytase
• ISSN: 0032-079X; 1573-5036
• DOI: 10.1007/s11104-022-05405-5

Purpose Organic anions commonly released from plant roots and microorganisms are widely reported to mobilize soil phosphorus (P). We characterized soil organic P that was mobilized by organic anions and assessed its amenability to hydrolysis by phosphatase enzymes. Methods Six soils differing in organic P concentration were extracted with citrate, malate or oxalate solutions and incubated with preparations of phosphomonoesterase, phosphodiesterase, or phytase. Organic P compounds present in these extracts were putatively identified and quantified with solution 31 P-NMR spectroscopy and the enzyme-labile P fractions were assessed by changes in molybdate-reactive P (MRP) concentration. Results Organic P mobilization varied markedly among the organic anions. Extraction with 10 mM citrate was most effective and extracted 7.8-fold more total P than the water controls across all soils. Approximately 95% of the extracted P was non-MRP. The organic anions increased both the amount of P extracted and the proportion of the total extracted P that was phosphatase-labile. Phytase was generally the most effective enzyme with up to 60% of the total non-MRP being amenable to hydrolysis by phytase across all extracts. The presence of inositol hexakisphosphates in the extracts, as well as other forms of organic P including nucleic acids and phospholipids, was verified by 31 P-NMR with concentrations dependent on both organic anions and soil type. Conclusion The combination of organic anions and phosphatases represents a key mechanism by which plants and microorganisms can enhance the bioavailability of soil P. This has important implications for understanding P dynamics in natural and managed ecosystems and for ongoing efforts to improve the P-acquisition efficiency of agricultural plants.