College of Life Sciences, Nanjing Agricultural University, Nanjing 210095, China.
Metallomics. 2017 Jul 19;9(7):936-948. doi: 10.1039/c7mt00072c.
Arbuscular mycorrhizal fungi (AMF) are widespread soil fungi that can form endosymbiotic structures with the root systems of most plants and can improve the tolerance of host plants to heavy metals. In the present study, we investigated the effects of AMF (Glomus coronatum) inoculation on the tolerance of Tagetes patula L. to Cu. Almost all of the non-mycorrhizal plants exposed to 100 μM Cu died after 3 d, whereas phytotoxicity was only observed in mycorrhizal plants that were exposed to Cu concentrations greater than 100 μM. Analysing the dynamic accumulation of Cu indicated that, after 7 d of Cu exposure, less Cu was absorbed or accumulated by mycorrhizal plants than by control plants, and significantly less Cu was translocated to the shoots. Meanwhile, analysing the root morphology, the integrity of the root plasma membranes, the photosynthesis rate, and the content of essential elements of plants growing in cultures with 50 μM Cu revealed that AMF inoculation markedly alleviated the toxic effects of Cu stress on root system activity, photosynthesis rate, and mineral nutrient accumulation. In addition, to understand the Cu allocation, an energy spectrum analysis of Cu content at the transverse section of root tips was conducted and subsequently provided direct evidence that intraradical hyphae at the root endodermis could selectively immobilise large amounts of Cu. Indeed, the sorption and barrier mechanisms of AMF hyphae reduce Cu toxicity in the roots of T. patula and eventually enhance the plants' Cu tolerance.
丛枝菌根真菌（AMF）是广泛存在于土壤中的真菌，能与大多数植物的根系形成共生结构，并能提高宿主植物对重金属的耐受性。本研究探讨了丛枝菌根真菌（Glomus coronatum）接种对万寿菊（Tagetes patula L.）对 Cu 耐受性的影响。在 100 μM Cu 暴露下，几乎所有非菌根植物在 3 天后死亡，而只有在 Cu 浓度大于 100 μM 时才观察到菌根植物的毒性。对 Cu 动态积累的分析表明，在 Cu 暴露 7 天后，菌根植物吸收或积累的 Cu 少于对照植物，且向地上部的转运明显减少。同时，分析根形态、根质膜完整性、光合作用速率和在 50 μM Cu 培养条件下植物必需元素含量表明，AMF 接种显著缓解了 Cu 胁迫对根系活力、光合作用速率和矿物质养分积累的毒害作用。此外，为了了解 Cu 的分配，对根尖横切面的 Cu 含量进行了能谱分析，随后提供了直接证据表明，根内皮层的根内菌丝可以选择性地固定大量的 Cu。事实上，AMF 菌丝的吸附和屏障机制降低了 T. patula 根部的 Cu 毒性，最终增强了植物的 Cu 耐受性。
