Abstract Excess salt in the soil induces oxidative injury in plant cells. Arbuscular mycorrhizal (AM) fungi can impart host plants salt tolerance and mitigate the oxidative injury in the plants exposed to salt stress. In order to clarify the effects of AM symbiosis on antioxidant activities in Robinia pseudoacacia under salt stress conditions and explore the molecular mechanisms involved, the biomass production and oxidative injury, concentrations of H2O2 and non-enzymatic antioxidants (ascorbate and glutathione), activities of antioxidant enzymes as well as expression of five antioxidant enzyme-encoding genes (RpCu/Zn-SOD, RpMn-SOD, RpAPX1, RpAPX2 and RpGR) in R. pseudoacacia inoculated with or without AM fungi under salt stress were analysed. The results showed that salinity reduced the biomass production in both NM and AM plants, but the reduction was lower in AM plants than in NM plants. In leaves, the levels of REL, MDA and H2O2 were reduced by AM symbiosis. Meanwhile, the activities of almost all enzymes tested (except for POX, which was unaffected by AM symbiosis), the expression of five antioxidant enzyme-encoding genes and the concentrations of total, reduced and oxidized ascorbate and glutathione were increased by AM symbiosis. However, in roots, the H2O2 accumulation was upregulated by mycorrhizal colonization. Moreover, the activities of APX and MDHAR and concentrations of total, reduced and oxidized ascorbate were downregulated by AM symbiosis. In addition, the root MDA level was similar in NM and AM plants. The results of present study suggest that the mitigation of oxidative injury in R. pseudoacacia by AM symbiosis was more evident in leaves than in roots. The greater ability of AM plants to counteract oxidative stress resulted in the improved growth performance and salt tolerance of these plants under salt stress.

中文翻译：

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丛枝菌根共生通过调节植物的抗氧化防御减轻盐胁迫下刺槐的氧化损伤

摘要 土壤中过量的盐分会引起植物细胞的氧化损伤。丛枝菌根 (AM) 真菌可以赋予宿主植物耐盐性并减轻暴露于盐胁迫的植物的氧化损伤。为了阐明AM共生对盐胁迫条件下刺槐抗氧化活性的影响，并探讨其分子机制、生物量产生和氧化损伤、H2O2和非酶抗氧化剂（抗坏血酸和谷胱甘肽）浓度、抗氧化活性酶以及五种抗氧化酶编码基因（RpCu/Zn-SOD、RpMn-SOD、RpAPX1、RpAPX2 和 RpGR）在盐胁迫下接种或不接种 AM 真菌的刺槐中的表达进行了分析。结果表明，盐度降低了 NM 和 AM 植物的生物量产量，但 AM 植物的减少量低于 NM 植物。在叶子中，AM 共生降低了 REL、MDA 和 H2O2 的水平。同时，几乎所有测试的酶的活性（除了不受 AM 共生影响的 POX），5 个抗氧化酶编码基因的表达以及总、还原和氧化抗坏血酸和谷胱甘肽的浓度都因 AM 共生而增加。然而，在根中，H2O2 积累被菌根定植上调。此外，APX 和 MDHAR 的活性以及总的、还原的和氧化的抗坏血酸的浓度被 AM 共生下调。此外，NM 和 AM 植物的根 MDA 水平相似。本研究的结果表明，AM 共生对刺槐氧化损伤的缓解在叶片中比在根中更明显。