Michigan State University, 310 Plant Research Laboratory, MI, East Lansing, USA.
University of Louisville, 139 Life Sciences Building, 40292, Louisville, KY, 40208, USA.
Mycorrhiza. 2021 Mar;31(2):251-258. doi: 10.1007/s00572-020-00992-6. Epub 2020 Oct 26.
The abiotic environment can dictate the relative costs and benefits of plant-arbuscular mycorrhizal fungi (AMF) symbioses. While the effects of varying light or soil nutrient conditions are well studied, outcomes of plant-AMF interactions along soil moisture gradients are not fully understood. It is predicted that mycorrhizal associations may become parasitic in extreme soil moisture conditions. Under low soil moisture stress, costs of maintaining a mycorrhizal symbiont may outweigh benefits for the host plant, whereas under high soil moisture stress, the host plant may not need the symbiont. In a factorial growth chamber study, we investigated the effects of a plant-arbuscular mycorrhizal fungus symbiosis along a soil moisture gradient on growth, cell wall chemistry, and root architecture of a biofuel crop, Panicum virgatum (switchgrass). Regardless of soil moisture conditions, we found an increase in the number of tillers, number of leaves, root biomass, and amount of cellulose and hemicellulose in response to root colonization by the arbuscular mycorrhizal fungus. The fungus also increased aboveground biomass and changed several root architectural traits, but only under low soil moisture conditions, indicating a reduction in benefits of the mycorrhizal association under high soil moisture. Results from this study indicate that an arbuscular mycorrhizal fungus can increase some key measures of plant growth and cell wall chemistry regardless of soil moisture conditions but is most beneficial in low soil moisture conditions.
非生物环境可以决定植物-丛枝菌根真菌（AMF）共生的相对成本和收益。虽然光照或土壤养分条件变化的影响已经得到了很好的研究，但植物-AMF 相互作用沿着土壤水分梯度的结果还不完全清楚。据预测，在极端土壤水分条件下，菌根共生可能会变得寄生。在低土壤水分胁迫下，维持菌根共生体的成本可能超过宿主植物的收益，而在高土壤水分胁迫下，宿主植物可能不需要共生体。在一个析因生长室研究中，我们调查了植物-丛枝菌根真菌共生体沿着土壤水分梯度对生物燃料作物柳枝稷（Panicum virgatum）生长、细胞壁化学和根系结构的影响。无论土壤水分条件如何，我们发现根被丛枝菌根真菌定殖后，分蘖数、叶片数、根生物量、纤维素和半纤维素的含量都会增加。真菌还增加了地上生物量，并改变了几个根系结构特征，但仅在低土壤水分条件下，这表明在高土壤水分条件下，菌根共生的收益减少。本研究的结果表明，丛枝菌根真菌可以增加一些关键的植物生长和细胞壁化学指标，而与土壤水分条件无关，但在低土壤水分条件下最有益。
