College of Resources and Environment, Centre of Excellence for Soil Biology, Southwest University, 2 Tiansheng Road, Beibei, Chongqing 400715, China.
College of Resources and Environment, Centre of Excellence for Soil Biology, Southwest University, 2 Tiansheng Road, Beibei, Chongqing 400715, China.
Ecotoxicol Environ Saf. 2021 Apr 15;213:112042. doi: 10.1016/j.ecoenv.2021.112042. Epub 2021 Feb 16.
Aluminum (Al) toxicity severely decreases plant growth and productivity in acidic soil globally. Ectomycorrhizal (ECM) fungi can promote host plant's Al-tolerance by acting as a physical barrier or bio-filter. However, little information is available on the role of ECM fungus on Al immobilization with respect to Al-tolerance. This present study aimed to screen a promising indigenous ECM fungus with high Al-tolerance and to understand its role in Al immobilization related to Al-tolerance. Two ECM fungal strains (Lactarius deliciosus 2 and Pisolithus tinctorius 715) isolated from forest stands in Southwest China were cultured in vitro with 0.0, 1.0 or 2.0 mM Al addition for 21 days to compare their Al accumulation and Al-tolerance. Meanwhile, fungal mycelia were incubated in 0.037 mM Al solutions, and then Al concentrations in the solution were determined at time 2, 5, 10, 20, 40, 60, 120, 180, and 240 min, and the Al immobilization characteristics were evaluated using the pseudo-first order, pseudo-second order and intraparticle diffusion models. Results showed that 1.0 or 2.0 mM Al addition significantly increased fungal biomass production by 23% or 41% in L. deliciosus 2, not in P. tinctorius 715. Fungal Al concentrations in L. deliciosus 2 and P. tinctorius 715 were significantly increased by 293% and 103% under 2.0 mM than under 1.0 mM Al addition. The pH values in the culture solution were significantly decreased by 0.43 after 21 d fungus growth but no changes between these two fungi under the same Al addition. Fungal Al immobilization showed a three-stage trend with initially a rapid rate followed a relatively slower rate until reaching equilibrium. The pseudo-second order model was the best (R = 0.98 and 0.99 for L. deliciosus 2 and P. tinctorius 715) to fit the experimentally observed data among the three models. Compared to P. tinctorius 715, L. deliciosus 2 also had greater intercept value, cation exchange capacity (CEC), and extracellular Al proportion in fungal mycelia. Additionally, bio-concentration on Al, active site numbers for Al, boundary layer thickness, CEC, and immobilization on the cell wall in fungal mycelia were involved in ECM fungal Al-tolerance. These results show that both ECM fungi are Al-tolerant while L. deliciosus 2 is a promising indigenous ECM isolate with higher Al-tolerance in Southwest China, and they can be hence applied to the afforestation and ecological restoration in acidic soil.
铝（Al）毒性会严重降低全球酸性土壤中植物的生长和生产力。外生菌根（ECM）真菌可以通过充当物理屏障或生物过滤器来促进宿主植物的耐铝性。然而，关于 ECM 真菌在耐铝性方面对铝固定的作用，相关信息仍然很少。本研究旨在筛选一种具有高耐铝性的有前景的本土 ECM 真菌，并了解其在耐铝性相关的铝固定中的作用。从中国西南地区的森林中分离出两种 ECM 真菌菌株（美味乳菇 2 和石生花 715），在体外分别用 0.0、1.0 或 2.0 mM Al 处理 21 天，以比较它们的 Al 积累和耐铝性。同时，将真菌菌丝体在 0.037 mM Al 溶液中孵育，然后在 2、5、10、20、40、60、120、180 和 240 分钟时测定溶液中的 Al 浓度，并使用拟一级、拟二级和内扩散模型评估 Al 固定特征。结果表明，1.0 或 2.0 mM Al 添加量分别使美味乳菇 2 的真菌生物量增加了 23%或 41%，而在石生花 715 中则没有增加。在 2.0 mM Al 处理下，美味乳菇 2 和石生花 715 的真菌 Al 浓度分别比 1.0 mM Al 处理下增加了 293%和 103%。在 21 天的真菌生长后，培养液的 pH 值显著降低了 0.43，但在相同的 Al 添加量下，两种真菌之间没有变化。真菌 Al 固定表现出三阶段趋势，最初是快速，然后是相对较慢，直到达到平衡。在三种模型中，拟二级模型是拟合实验观察数据的最佳模型（美味乳菇 2 和石生花 715 的 R 值分别为 0.98 和 0.99）。与石生花 715 相比，美味乳菇 2 还具有更大的截距值、阳离子交换容量（CEC）和真菌菌丝中细胞外 Al 比例。此外，ECM 真菌的耐铝性涉及 Al 的生物浓缩、Al 的活性位点数量、边界层厚度、CEC 和细胞壁的固定。这些结果表明，这两种 ECM 真菌均具有耐铝性，而美味乳菇 2 是一种在中国西南地区具有更高耐铝性的有前景的本土 ECM 分离株，可应用于酸性土壤的造林和生态恢复。
