Phytate (Inositol Hexakisphosphate) in Soil and Phosphate Acquisition from Inositol Phosphates by Higher Plants. A Review.
Phytate (Inositol Hexakisphosphate) in Soil and Phosphate Acquisition from Inositol Phosphates by Higher Plants. A Review.
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DOI：
10.3390/plants4020253
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发表时间：
2015-05-22
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影响因子：
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通讯作者：
Gerke J
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文献类型：
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作者：
Gerke J
土壤固磷被认为是磷有效性的重要因素，通常归因于正磷酸根阴离子的强结合。然而，肌醇六磷酸和五磷酸异构体（植酸盐）在土壤中的固定和随后的固定化往往比原磷酸盐阴离子物种强得多。结果表明，植酸盐是土壤中主要的有机磷形态，也是可识别有机磷的主要形态。在过去的20年中，在文献中可以发现两种假说，一种是土壤中植酸酶（磷酸酶）的低活性，这使得植物根部不能利用植酸盐P，另一种是植酸盐与土壤固相的强结合，从而使其在土壤中稳定和积累。低植酸酶活性是导致植酸积累的假设导致了在根表面具有更高植酸酶活性表达的转基因植物基因型的发展，并研究了更高的植酸酶活性对P获得的影响。显然，这一假说有一个基本假设，即植酸在土壤中的移动性不是高等植物从土壤植酸中获得磷的限制步骤。然而，考虑到过去20年中报道的植酸盐在土壤固相中的吸附、固定和固定的结果，这种假设是不合理的。植酸是强烈绑定，和磷的吸附最大值和可能的植酸磷的吸附强度的土壤固相要高得多，相比，正磷酸盐P.植酸的动员似乎是一个很有前途的步骤，使其提供给植物根系。有机酸阴离子的排泄，柠檬酸盐和较小程度的草酸盐，似乎是一个重要的途径，使植酸磷提供给植物。在根表面的植酸酶活性似乎不是从植酸磷收购的限制步骤。植酸盐不仅与土壤中的无机表面结合，而且与正磷酸盐类似，也可以通过Fe或Al桥与腐殖表面结合。腐殖酸-金属-植酸盐复合物可以在土壤溶液中运输到根部，在那里可以发生水解和吸收释放的P。强烈需要对这一主题进行研究。
Phosphate (P) fixation to the soil solid phase is considered to be important for P availability and is often attributed to the strong binding of orthophosphate anion species. However, the fixation and subsequent immobilization of inositolhexa and pentaphosphate isomers (phytate) in soil is often much stronger than that of the orthosphate anion species. The result is that phytate is a main organic P form in soil and the dominating form of identifiable organic P. The reasons for the accumulation are not fully clear. Two hypothesis can be found in the literature in the last 20 years, the low activity of phytase (phosphatases) in soil, which makes phytate P unavailable to the plant roots, and, on the other hand, the strong binding of phytate to the soil solid phase with its consequent stabilization and accumulation in soil. The hypothesis that low phytase activity is responsible for phytate accumulation led to the development of genetically modified plant genotypes with a higher expression of phytase activity at the root surface and research on the effect of a higher phytate activity on P acquisition. Obviously, this hypothesis has a basic assumption, that the phytate mobility in soil is not the limiting step for P acquisition of higher plants from soil phytate. This assumption is, however, not justified considering the results on the sorption, immobilization and fixation of phytate to the soil solid phase reported in the last two decades. Phytate is strongly bound, and the P sorption maximum and probably the sorption strength of phytate P to the soil solid phase is much higher, compared to that of orthophosphate P. Mobilization of phytate seems to be a promising step to make it available to the plant roots. The excretion of organic acid anions, citrate and to a lesser extend oxalate, seems to be an important way to make phytate P available to the plants. Phytase activity at the root surface seems not be the limiting step in P acquisition from phytate. Phytate is not only bound to inorganic surfaces in soil but can also be bound, similar to orthophosphate, to humic surfaces via Fe or Al bridges. Humic-metal-phytate complexes may be transported in the soil solution to the roots where hydrolysis and uptake of the liberated P may occur. Research on this topic is strongly required.