摘要
植酸(myo-inositol hexakisphosphate,肌醇六磷酸)是一种有机磷类化合物,是土壤磷库的重要组成部分,占土壤有机磷的50％～80％,总磷的20％～50％.然而,植酸分子含有6个磷酸基团,具有强络合能力,极易被土壤矿物(针铁矿、赤铁矿、勃姆石等)吸附形成难溶性或不溶性络合物,导致生物可利用性极低.植酸-矿物络合物的形成及稳定性决定了植酸被活化和利用的难易程度,该过程受植酸浓度、pH值、环境温度、络合方式、参与配位的磷酸基团数、吸附亲和力及土壤矿物种类等因素的影响.植物根系和微生物分泌的有机酸(柠檬酸、草酸等),可通过竞争吸附、络合、溶解等方式活化络合物中的植酸,并释放与植酸络合的矿质元素,提高土壤中磷和矿质元素的生物可利用性,对减少外源磷肥施用和降低磷流失污染风险具有重要的现实意义.因此,本文通过综述土壤中植酸-矿物络合物的形成过程与影响因素(植酸浓度、环境介质pH值、环境温度)、稳定性及其影响因素(络合方式、矿物类型),重点阐述有机酸活化植酸-矿物络合物的机制(配体交换、竞争吸附、氢键作用、溶解作用等)、效率及影响因素(络合物种类、稳定性及植酸吸附密度,有机酸种类与浓度,环境pH值),以期为提高土壤内源植酸磷的生物有效性和利用率提供理论依据和技术参考.
Abstract
Phytic acid or phytate(myo-inositol hexakisphosphate),a kind of organic phosphorus(Po),is an important P pool in soils,accounting for 50％-80％of Po and 20％-50％of total P.However,phytate contains 6 phosphate groups,which has strong complexing ability and is readily being adsorbed by soil solid matrix(goethite,hematite,and boehmite)to form poorly-soluble or insoluble complexes,resulting in low bioavailability.The formation and stability of phytate-mineral complexes determines the mobilization and utilization efficiency of phytate,which is influenced by various factors including phytate concentration,pH,temperature,complexation ways,number of phosphate groups participated in coordi-nation,adsorption affinity,and soil mineral types.Plant roots and microorganisms secrete organic acids like citrate and ox-alate,which can release phytate and mineral elements from the complexes via competitive adsorption,complexation and dissolution.The improved bioavailability of phytate-P and mineral elements helps to reduce exogenous P fertilizer applica-tion and P pollution risk,which is of great environmental and practical importance.Therefore,this paper reviews phytate-mineral complexes formation process and the associated influencing factors(phytate concentration,pH and temperature)and complexes stability and the associated influencing factors(adsorption mode and mineral species).In addition,the ef-ficiency and mechanism of organic acids-mediated mobilization of phytate-mineral complexes(ligand exchange,competitive adsorption,hydrogen bonding and dissolution)and the associated influencing factors(complexes type and sta-bility,phytate adsorption density,organic acid species and concentration,and pH)were illustrated.The information helps to provide theoretical and technical supports to improve the bioavailability and utilization of soil endogenous phytate-P.
基金项目
云南省农业联合专项(202101BD070001-043)
国家自然科学基金(41867066)
国家自然科学基金(41907129)
维普
万方数据