Role of root‐induced changes in the rhizosphere for iron acquisition in higher plants
Role of root‐induced changes in the rhizosphere for iron acquisition in higher plants
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根诱导的根际变化对高等植物铁获取的作用
DOI：
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发表时间：
1989
期刊：
影响因子：
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通讯作者：
V. Römheld
中科院分区：
文献类型：
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作者：
H. Marschner;M. Treeby;V. Römheld
植物可以通过非特异性和特异性（适应性）机制动员根际铁（Fe）。非特异性机制是，例如，根际酸化与高阳离子-阴离子吸收比，或柠檬酸排泄。其具体机制是根系对缺铁的反应，并可分为两种不同的策略。策略I是典型的双子叶植物和单子叶植物，除了草（禾本科物种），其特征在于增加质膜结合还原酶活性，增强质子的净排泄和增强释放的还原化合物，主要是酚类。还原酶活性的刺激低pH值，并与FeIII螯合物的供应，铁还原在质膜发生之前的吸收。相反，在禾本科物种（策略II），这些根的反应是不存在的，但增强释放的Fe III螯合化合物-植物铁载体-发生。这些植物铁载体在从人工制备的微溶无机化合物（例如Fe III氢氧化物）和石灰性土壤中动员Fe III方面非常有效。高铁植物铁载体被草吸收的速率比作为合成螯合物或微生物铁载体（例如铁草胺B）提供的Fe高102至103倍，表明草根中高铁植物铁载体的特定膜运输系统。在石灰性土壤中，植物铁载体不仅能活化Fe，还能螯合Zn、Mn和Cu。然而，只有Fe III植物铁载体优先采取了缺铁草。讨论了从石灰性土壤中获取铁的策略I和策略II的生态优势和劣势。
Plants can mobilize iron (Fe) in the rhizosphere by non-specific and specific (adaptive) mechanisms. Non-specific mechanisms are, for example, rhizosphere acidification related to high cation-anion uptake ratios, or citric acid excretion. The specific mechanisms are root responses to Fe deficiency and can be classified into two different strategies. The Strategy I is typical for dicots and monocots except for grasses (graminaceous species) and is characterized by increased plasma membrane-bound reductase activity, enhanced net excretion of protons and enhanced release of reducing compounds, mainly phenolics. The reductase activity is stimulated by low pH, and with supply of FeIII chelates, ferric reduction at the plasma membrane takes place prior to uptake. In contrast, in graminaceous species (Strategy II) these root responses are absent, but enhancement of release of FeIII chelating compounds - phytosiderophores - takes place. These phytosiderophores are very efficient in mobilizing FeIII from artificially prepared sparingly soluble inorganic compounds (e.g. FeIII hydroxide) and from calcareous soils. The ferrated phytosiderophores are taken up by grasses at rates 102 to 103 times higher than Fe supplied either as synthetic chelate or microbial siderophores (e.g. ferrioxamine B), indicating a specific membrane transport system for ferrated phytosiderophores in roots of grasses. In calcareous soils phytosiderophores not only mobilize Fe, but also Zn, Mn, and Cu by chelation. However, only the FeIII phytosiderophores are taken up preferentially by Fe deficient grasses. The ecological advantages and disadvantages of Strategy I and Strategy II for Fe acquisition from calcareous soils are discussed.