• ISSN 1008-505X
  • CN 11-3996/S

有机酸提高土壤植酸生物有效性的机制、影响因素及应用

Mechanism, influencing factors and practical application of organic acids in improving soil phytate bioavailability

  • 摘要: 土壤中的植酸主要来源于植物残体和单胃动物排泄物,可被专一性酶—植酸酶(myo-inositol hexakisphate phosphohydrolase)矿化水解,经脱磷酸化过程释放无机磷供植物吸收。植酸是土壤有机磷的重要组成部分,占有机磷总量的50%~80%。植酸分子中含有6个磷酸基团和12个可解离质子,极易被土壤吸附或与金属离子形成难溶性络合物,阻止其与植酸酶接触,极大降低了植酸的分解矿化效率,难以为植物提供磷素营养。因此,提高植酸的溶解性和生物有效性是保障土壤供磷效率的重要前提。土壤中的有机酸主要来源于植物根系、微生物释放及有机质分解。有机酸含有的多种官能团可与金属离子络合形成更稳定的金属配合物,通过竞争吸附、络合作用、断裂有机质−金属架桥等,将吸附态植酸或植酸金属络合物活化释放,实现植酸磷的解吸和活化。土壤中有机酸的种类和含量因植物和微生物种类而异,土壤pH、有机质含量、土壤矿物/金属氧化物种类与含量等均影响有机酸对植酸的活化效率。因此,后续研究可关注:1)不同有机酸对不同类型土壤中植酸的活化效率,定量分析有机酸种类和浓度对土壤植酸的解吸量和活化效率;2)被植酸强吸附的矿物表面在较大pH范围内具有较高的负电荷,阻碍有机酸的吸附和置换反应,因此需要深入探究提高有机酸活化强吸附态植酸的技术和方法;3)需监测和评估有机酸活化土壤植酸的长期效应。

     

    Abstract: Phytate in soils mainly origins from plant residues and monogastric animal excrement. The phytate can only be mineralized to release P through hydrolysis and dephosphorylation, which are catalysed by specific enzymes-phytase (myo-inositol hexakisphate phosphohydrolase). Phytic acids or phytate, are important components of soil organic phosphorus, accounting for 50%–80% of total organic P. Phytic acids contain 6 phosphate groups and 12 dissociable protons, thus readily being adsorbed by soils or form insoluble complexes with metal ions. Consequently, phytic acids are prevented from interactions with phytase, their decomposition and mineralization efficiency are thus decreased greatly, hard to release P for plant uptake. Improving the solubility and bioavailability of phytate is one of the prerequisites to ensure the efficient P supply of soil to crops. Soil organic acids are derived from plant root excretes, microorganisms, and organic matter decomposition. Organic acids have plenty of functional groups, which can form more stable ligand complexes with metal ions, therefore, mobilize the adsorbed phytate or phytate-metal complexes through competitive adsorption, complexation, and fracturing organic matter-metal bridges. The kinds and contents of soil organic acids varied, depending on plant and microbe species. Besides, soil pH, organic matter content, the types and contents of soil minerals/metal oxides all influence the mobilization efficiency of organic acids-mediated phytate. As such, further studies should work on the following points: 1) Phytate mobilization efficiency of different organic acids in different types of soils. Quantitatively analyze phytate desorption and mobilization efficiency by different kinds and concentrations of organic acids. 2) Phytate-adsorped mineral surface is highly negative charged in wide pH ranges, which hinders the adsorption and displacement reactions of organic acids. Therefore, it is necessary to explore strategies to improve the mobilization of adsorbed-phytate. 3) Monitoring and evaluate the long-term performance of organic acids-mediated phytate mobilization.

     

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