Plants, Photosynthesis and Soil, School of Biosciences, University of Sheffield, Sheffield, South Yorkshire S10 2TN, UK.
Plants, Photosynthesis and Soil, School of Biosciences, University of Sheffield, Sheffield, South Yorkshire S10 2TN, UK; School of Biology and Environmental Science, University College Dublin, Dublin, County Dublin D4, Ireland.
Curr Biol. 2023 Jun 19;33(12):2566-2573.e4. doi: 10.1016/j.cub.2023.05.033. Epub 2023 Jun 7.
Arbuscular mycorrhizal fungi colonize the roots of most plants, forming a near-ubiquitous symbiosis that is typically characterized by the bi-directional exchange of fungal-acquired nutrients for plant-fixed carbon. Mycorrhizal fungi can form below-ground networks with potential to facilitate the movement of carbon, nutrients, and defense signals across plant communities. The importance of neighbors in mediating carbon-for-nutrient exchange between mycorrhizal fungi and their plant hosts remains equivocal, particularly when other competing pressures for plant resources are present. We manipulated carbon source and sink strengths of neighboring pairs of host plants through exposure to aphids and tracked the movement of carbon and nutrients through mycorrhizal fungal networks with isotope tracers. When carbon sink strengths of both neighboring plants were increased by aphid herbivory, plant carbon supply to extraradical mycorrhizal fungal hyphae was reduced, but mycorrhizal phosphorus supply to both plants was maintained, albeit variably, across treatments. However, when the sink strength of only one plant in a pair was increased, carbon supply to mycorrhizal fungi was restored. Our results show that loss of carbon inputs into mycorrhizal fungal hyphae from one plant may be ameliorated through inputs of a neighbor, demonstrating the responsiveness and resilience of mycorrhizal plant communities to biological stressors. Furthermore, our results indicate that mycorrhizal nutrient exchange dynamics are better understood as community-wide interactions between multiple players rather than as strict exchanges between individual plants and their symbionts, suggesting that mycorrhizal C-for-nutrient exchange is likely based more on unequal terms of trade than the "fair trade" model for symbiosis.
丛枝菌根真菌定殖于大多数植物的根部，形成一种近乎普遍存在的共生关系，其典型特征是真菌获得的养分与植物固定的碳的双向交换。菌根真菌可以在地下形成网络，有可能促进碳、养分和防御信号在植物群落中的传递。在存在其他植物资源竞争压力的情况下，邻居在调节菌根真菌与其植物宿主之间的碳换养分方面的重要性仍然存在争议。我们通过蚜虫暴露来操纵相邻宿主植物的碳源和碳汇强度，并通过同位素示踪剂跟踪碳和养分通过菌根真菌网络的移动。当蚜虫取食增加了相邻植物的碳汇强度时，植物向菌根真菌外生菌丝的碳供应减少，但菌根真菌向两种植物的磷供应得到维持，尽管在处理中有所不同。然而，当一对植物中只有一株的碳汇强度增加时，菌根真菌的碳供应得到恢复。我们的研究结果表明，一株植物向菌根真菌菌丝输入的碳损失可能通过邻居的输入得到缓解，这表明菌根植物群落对生物胁迫具有响应性和弹性。此外，我们的研究结果表明，菌根养分交换动态更好地理解为多个参与者之间的社区范围的相互作用，而不是作为个体植物与其共生体之间的严格交换，这表明菌根 C 换养分交换更可能基于不平等的贸易条件，而不是共生关系的“公平贸易”模式。
