Soils Group, School of Agriculture, Food and Wine, University of Adelaide, Waite Campus, Adelaide, South Australia 5005, Australia.
Annu Rev Plant Biol. 2011;62:227-50. doi: 10.1146/annurev-arplant-042110-103846.
Root systems of most land plants form arbuscular mycorrhizal (AM) symbioses in the field, and these contribute to nutrient uptake. AM roots have two pathways for nutrient absorption, directly through the root epidermis and root hairs and via AM fungal hyphae into root cortical cells, where arbuscules or hyphal coils provide symbiotic interfaces. New physiological and molecular evidence shows that for phosphorus the mycorrhizal pathway (MP) is operational regardless of plant growth responses (positive or negative). Amounts delivered cannot be determined from plant nutrient contents because when responses are negative the contribution of the direct pathway (DP) is reduced. Nitrogen (N) is also delivered to roots via an MP, but the contribution to total N requirement and the costs to the plant are not clear. The functional interplay between activities of the DP and MP has important implications for consideration of AM symbioses in ecological, agronomic, and evolutionary contexts.
大多数陆生植物的根系在野外形成丛枝菌根（AM）共生体，这有助于养分吸收。AM 根有两种养分吸收途径，一种是通过根表皮和根毛直接吸收，另一种是通过 AM 真菌菌丝进入根皮层细胞，在那里丛枝或菌丝环提供共生界面。新的生理和分子证据表明，对于磷来说，无论植物生长反应（正向或负向）如何，菌根途径（MP）都是起作用的。由于当反应为负时，直接途径（DP）的贡献减少，因此无法从植物养分含量中确定输送的量。氮（N）也通过 MP 输送到根部，但对总 N 需求的贡献和对植物的成本尚不清楚。DP 和 MP 活性之间的功能相互作用对在生态、农业和进化背景下考虑 AM 共生体具有重要意义。
