Roles of Arbuscular Mycorrhizas in Plant Phosphorus Nutrition: Interactions between Pathways of Phosphorus Uptake in Arbuscular Mycorrhizal Roots Have Important Implications for Understanding and Manipulating Plant Phosphorus Acquisition

作者：Sally E. Smith, Iver Jakobsen, Mette Grønlund, F. A. SMITH · 发表于：PLANT PHYSIOLOGY · 年份：2011 · DOI：10.1104/pp.111.174581 · 被引用次数：1251 · 研究领域：Plant nutrient uptake and metabolism、Mycorrhizal Fungi and Plant Interactions、Legume Nitrogen Fixing Symbiosis

In this Update, we review new findings about the roles of the arbuscular mycorrhizas (mycorrhiza = fungus plus root) in plant growth and phosphorus (P) nutrition. We focus particularly on the function of arbuscular mycorrhizal (AM) symbioses with different outcomes for plant growth (from positive to negative) and especially on the interplay between direct P uptake via root epidermis (including root hairs when present) and uptake via the AM fungal pathway. The results are highly relevant to many aspects of AM symbiosis, ranging from signaling involved in the development of colonization and the regulation of P acquisition to the roles of AM fungi in determining the composition of natural plant assemblages in ecological settings and their changes with time. P is critical for plant growth and makes up about 0.2% of dry weight, but it is one of the most difficult nutrients for plants to acquire. In soil, it may be present in relatively large amounts, but much of it is poorly available because of the very low solubility of phosphates of iron, aluminum, and calcium, leading to soil solution concentrations of 10 μm or less and very low mobility (Schachtman et al., 1998). In consequence, uptake of orthophosphate (Pi) by root epidermal cells including root hairs (the direct pathway) leads to lowering of Pi concentrations in the rhizosphere (so-called depletion zones), because replacement does not keep pace with uptake (Fig. 1). Plants and fungi take up P as negatively charged Pi ions (...