Institute for Evolutionary Biology and Environmental Studies, University of Zürich, Zürich, Switzerland.
Departement Umweltwissenschaften, University of Basel, Basel, Switzerland.
PLoS One. 2024 Jan 31;19(1):e0292811. doi: 10.1371/journal.pone.0292811. eCollection 2024.
Arbuscular mycorrhizal fungi (AMF) are plant root symbionts that provide phosphorus (P) to plants in exchange for photosynthetically fixed carbon (C). Previous research has shown that plants-given a choice among AMF species-may preferentially allocate C to AMF species that provide more P. However, these investigations rested on a limited set of plant and AMF species, and it therefore remains unclear how general this phenomenon is. Here, we combined 4 plant and 6 AMF species in 24 distinct plant-AMF species compositions in split-root microcosms, manipulating the species identity of AMF in either side of the root system. Using 14C and 32P/33P radioisotope tracers, we tracked the transfer of C and P between plants and AMF, respectively. We found that when plants had a choice of AMF species, AMF species which transferred more P acquired more C. Evidence for preferential C allocation to more beneficial AMF species within individual plant roots was equivocal. However, AMF species which transferred more P to plants did so at lower C-to-P ratios, highlighting the importance both of absolute and relative costs of P acquisition from AMF. When plants had a choice of AMF species, their shoots contained a larger total amount of P at higher concentrations. Our results thus highlight the benefits of plant C choice among AMF for plant P acquisition.
丛枝菌根真菌（AMF）是与植物根系共生的真菌，它们为植物提供磷（P），以换取植物光合作用固定的碳（C）。先前的研究表明，在 AMF 物种之间存在选择的情况下，植物可能会优先将 C 分配给提供更多 P 的 AMF 物种。然而，这些研究基于有限的植物和 AMF 物种，因此尚不清楚这种现象的普遍性如何。在这里，我们在分根微宇宙中组合了 4 种植物和 6 种 AMF 物种，在根系的两侧分别操纵 AMF 的物种身份。使用 14C 和 32P/33P 放射性同位素示踪剂，我们分别追踪了 C 和 P 在植物和 AMF 之间的转移。我们发现，当植物有 AMF 物种可供选择时，转移更多 P 的 AMF 物种获得了更多的 C。在单个植物根系内，对更有益的 AMF 物种进行优先 C 分配的证据是模棱两可的。然而，向植物转移更多 P 的 AMF 物种以较低的 C-to-P 比进行，这突出了绝对和相对 AMF 磷获取成本的重要性。当植物有 AMF 物种可供选择时，它们的地上部分含有更多的总磷，浓度也更高。因此，我们的研究结果强调了植物在 AMF 之间进行 C 选择以获取植物 P 的好处。
