接种外生菌根真菌对铝胁迫下马尾松幼苗细根抗氧化生理的影响

Ectomycorrhizal fungal inoculation alleviates aluminum stress in Pinus massoniana seedlings by modulating fine root antioxidant physiology

摘要:

目的 探索外生菌根真菌(ectomycorrhizal fungus, ECMF)侵染能否以及如何通过调控细根抗氧化生理来抵御铝毒，为将ECMF应用于酸铝地区的生态修复提供理论依据。 方法 选用松乳菇( Lactarius deliciosus) 2和彩色豆马勃( Pisolithus tinctorius) 715接种马尾松( Pinus massoniana)幼苗，以非菌根苗为对照，经0.0 mmol/L和1.0 mmol/L Al ³⁺连续处理6个月后取马尾松幼苗进行检测分析，内容包括其生物量、细根形态参数、质膜透性、活性氧水平、抗氧化酶活性与渗透调节物质含量。 结果 铝胁迫下接种 L. deliciosus 2和 P. tinctorius 715可显著促进马尾松幼苗生长和细根发育，幼苗生物量增加1.26-1.33倍，细根总根长、根表面积、根体积和根尖数增加2.25-3.99倍，细根丙二醛(malondialdehyde, MDA)、过氧化氢(hydrogen peroxide, H ₂O ₂)、脯氨酸和可溶性蛋白含量则显著降低。此外，接种 L. deliciosus 2还可显著增强细根过氧化物酶(peroxidase, POD)与过氧化氢酶(catalase, CAT)活性，且比接种 P. tinctorius 715具有更高的细根表面积、根体积和更低的脯氨酸含量。 结论 接种ECMF有助于提高马尾松幼苗抗铝毒能力，其核心驱动力在于促进细根形态发育，而减少H ₂O ₂积累、防止细胞膜功能受损、降低渗透调节物质合成是其中的关键。 L. deliciosus 2促进细根生长发育的能力强于 P. tinctorius 715，其POD与CAT活性增强以及脯氨酸合成量降低更有利于防止细根免受铝的原初毒害。

Abstract:

Objective Aluminum (Al) toxicity in acidic soils severely inhibits plant growth by inducing oxidative stress. Ectomycorrhizal fungus (ECMF) can enhance host plant Al tolerance, but the underlying physiological mechanisms, particularly in fine roots, are not fully understood. This study investigates how ECMF colonization mitigates Al toxicity by modulating the antioxidant physiology of plants, with an aim in applying ECMF for the ecological restoration of Al-contaminated acidic soils. Methods Pinus massoniana seedlings were inoculated with Lactarius deliciosus 2 or Pisolithus tinctorius 715, with non-ectomycorrhizal seedlings as the control. After a 6-month exposure to 0.0 mmol/L or 1.0 mmol/L Al ³⁺, we assessed seedling biomass, fine root morphology, plasma membrane permeability, reactive oxygen species (ROS) levels, antioxidant enzyme activities, and osmoregulatory substance content. Results Under Al stress, inoculation with either L. deliciosus 2 or P. tinctorius 715 significantly promoted seedling growth and fine root development. The inoculated seedlings exhibited 1.26-1.33 folds greater biomass and 2.25-3.99 folds increases in the total root length, root surface area, root volume, and root tip number compared to the non-inoculated control. The ECMF inoculation also significantly reduced the accumulation of malondialdehyde (MDA), hydrogen peroxide (H ₂O ₂), proline, and soluble proteins in fine roots. Furthermore, inoculation with L. deliciosus 2 resulted in significantly higher root surface area and root volume, along with greater peroxidase (POD) and catalase (CAT) activities and a more pronounced reduction in proline content in fine roots, compared to inoculation with P. tinctorius 715. Conclusion Our findings demonstrate that ECMF inoculation alleviates Al stress in P. massoniana seedlings by promoting fine root development, bolstering the antioxidant system (notably through increased POD and CAT activities), reducing H ₂O ₂ accumulation, preserving plasma membrane integrity, and decreasing the synthesis of osmoregulatory substances. The superior performance of L. deliciosus 2 highlights its potential for its application in the ecological restoration of Al-contaminated acidic soils.