铝和锰对外生菌根真菌生长、养分吸收及分泌作用的影响

在强酸性土壤和铝锰矿墟上,铝和锰是影响森林生长和植被恢复的主要限制因子,研究它们对外生菌根真菌的影响,筛选优良的抗性菌株,可为开展污染土壤生物修复提供技术支撑及理论依据.试验采用纯培养技术研究了Al3+、Mn2+单独或共存对褐环乳牛肝菌13(Suillus luteus 13,Sl 13)、土生空团菌04(Cenococcum geophilum 04,Cg 04)、彩色豆马勃715(Pisolithustinctorius 715,Pt 715)这3株外生菌根真菌生长、养分吸收、有机酸分泌的影响.结果表明,Mn2+使Sl 13、Cg 04、Pt 715的生物量分别降低了70.35%、52.44%和18.55%;Al3+使Sl 13的生物量下降50.74%,但增加Cg 04的生物量;Al3+和Mn2+共存对3种菌株生长均有协同抑制作用,但对Pt 715的抑制最小,表明Cg 04抗铝,Pt 715对铝、锰的单独污染和复合污染均有较强的抗性.Al3+和Mn2+抑制外生菌根真菌吸收养分,对Sl 13的抑制作用显著大于Pt 715和Cg 04;但提高3个菌株的草酸和H+分泌速率,增加其分泌量,两者共存对Cg 04草酸分泌速率具有协同促进效应,Pt 715不仅能分泌草酸而且还分泌丁二酸.因此,抗性强的外生菌根真菌可通过分泌较多的有机酸络合Al3+和Mn2+而缓解其毒害.

Influence of Aluminum and Manganese on the Growth, Nutrient Uptake and the Efflux by Ectomycorrhizal Fungi

Al³⁺ and Mn²⁺ limit forest growth and vegetation restoration in strongly acidic soils and mining areas of aluminum and manganese. The knowledge on the influence of these two elements on ectomycorrhizal fungi can provide theoretical and technical supports for the selection of powerful ectomycorrhizal fungal strains and the bioremediation of contaminated soil. Three ectomycorrhizal fungal strains, namely Suillus luteus 13 (Sl 13), Cenococcum geophilum 04 (Cg 04) and Pisolithus tinctorius 715 (Pt 715), were grown in liquid culture mediums with Al³⁺ and Mn²⁺ added alone and together to investigate fungal growth, nutrient uptake and organic acid efflux. The results showed that the biomass of Sl 13, Cg 04 and Pt 715 was decreased by 70.35%, 52.44% and 18.55%, respectively, under Mn²⁺ stress. Al³⁺ also decreased the biomass of Sl 13 by 50.74% but increased that of Cg 04.The growth of ectomycorrhizal fungi was further inhibited when grown in culture solutions with addition of both Mn²⁺ and Al³⁺ and the least growth inhibition was found with Pt 715.Cg 04 might thus have a strong resistance to Al³⁺ stress and Pt 715 to both Al³⁺ and Mn²⁺ compared to the others. Al³⁺ and Mn²⁺ decreased the nutrient uptake by the fungi, particularly by Sl 13 which showed more obvious reduction than Pt 715 and Cg 04.However, Al³⁺ and Mn²⁺ increased the efflux of oxalic acid and protons by ectomycorrhizal fungi. An additional oxalic acid exudation by Cg 04 was observed in the coexistence of Al³⁺ and Mn²⁺ and Pt 715 exuded not only oxalic acid but also succinic acid. Therefore, ectomycorrhizal fungi resistant to Mn²⁺ and Al³⁺ could effuse more organic acids than the sensitive ones in order to alleviate the harmfulness through complexation under the stress.