Background and aims

Salinity causes significant environmental stress that restricts plant growth and development, and arbuscular mycorrhizal fungi (AMF) can use different mechanisms to protect plants against salt stress. The aim of this study was to explore the local and systemic effects of AMF in alfalfa plants under uniform and non-uniform salinity and the abilities of the AMF that underlie these effects.

Methods

Alfalfa (Medicago sativa L.) plants were subjected to uniform (200/200 mM NaCl) and non-uniform (0/200 mM NaCl) salt stress using a split-root system, with one or both root compartments inoculated or not inoculated with the AMF Rhizophagus irregularis.

Results

We observed that the inoculation with AMF ameliorated the negative effects of salt stress by enhancing the dry weight, plant growth rate, photosynthesis, and the activities of antioxidant enzymes, including catalase, peroxidase, and superoxide dismutase. These effects contributed to maintaining an ionic and nutritive balance and resulted in lower levels of lipid peroxidation and contents of H₂O₂ under both uniform and non-uniform salinity treatments, particularly when the whole root system was inoculated with AMF. Under non-uniform salinity, when the high-saline root side was inoculated with AMF, the oxidative defense was restricted to that compartment, and the AMF played a key role in alleviating the damage caused by salt stress. Conversely, when AMF was inoculated on the non-saline root side, both root compartments exhibited systemic oxidative defense mechanisms, which highlighted the significance of functional equilibrium within the root system at enhancing salt tolerance.

Conclusion

The findings indicate that AMF ameliorates the effects of salt stress through distinct antioxidant defenses and ion regulatory mechanisms under non-uniform salinity. Phosphorus uptake and ion regulation were more effective in the AMF-inoculated root side under both the uniform and non-uniform salinity conditions.

中文翻译：

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丛枝菌根真菌在均匀和非均匀盐胁迫下控制紫花苜蓿生长、抗氧化防御和养分吸收的局部和内吸能力

 背景和目标

盐度会引起严重的环境压力，限制植物的生长和发育，而丛枝菌根真菌 （AMF） 可以使用不同的机制来保护植物免受盐胁迫。本研究的目的是探讨 AMF 在均匀和非均匀盐度下对紫花苜蓿植物的局部和全身影响，以及构成这些影响基础的 AMF 的能力。

 方法

紫花苜蓿 （Medicago sativa L.） 植物使用分根系统经受均匀 （200/200 mM NaCl） 和非均匀 （0/200 mM NaCl） 盐胁迫，一个或两个根室接种或不接种 AMF Rhizophagus irregularis。

 结果

我们观察到，接种 AMF 通过提高干重、植物生长速率、光合作用和抗氧化酶（包括过氧化氢酶、过氧化物酶和超氧化物歧化酶）的活性来改善盐胁迫的负面影响。这些影响有助于维持离子和营养平衡，并导致在均匀和非均匀盐度处理下脂质过氧化水平和 H₂O₂ 含量降低，特别是当整个根系接种 AMF 时。在不均匀盐度下，当高盐度根侧接种 AMF 时，氧化防御仅限于该隔室，AMF 在缓解盐胁迫造成的损伤方面发挥了关键作用。相反，当 AMF 接种在非盐碱根侧时，两个根区室都表现出全身性氧化防御机制，这突出了根系内功能平衡在增强耐盐性方面的重要性。

 结论

研究结果表明，在不均匀的盐度下，AMF 通过不同的抗氧化防御和离子调节机制改善盐胁迫的影响。在均匀和非均匀盐度条件下，接种 AMF 的根侧磷吸收和离子调节都更有效。