外生菌根真菌对土壤钾的活化作用

Mobilization of potassium from soil by ectomycorrhizal fungi

摘要:

摘要:【目的】外生菌根真菌是森林生态系统中的重要组成成分，与木本植物的根系形成菌根，参与树木养分吸收。【方法】试验在液培条件下，以土壤为钾源，利用我国西南地区分离的牛肝菌(Boletnus sp.，Bo 07)、松乳菇(Lactarius delicious，Ld 03)、彩色豆马勃(Pisolithus tinctorius，Pt 715)和内蒙古大青山分离的土生空团菌(Cenococcum geophilum，Cg 04)为材料，研究了它们的生长、钾吸收、氢离子和有机酸分泌，以及土壤钾的变化。【结果】结果表明，Bo 07、Ld 03和Pt 715的生物量、含钾量和吸收量显著高于Cg 04，说明在长期缺钾的环境中，外生菌根真菌经过“物竞天择”可能进化出适应低钾和较强的吸钾能力。以土壤为钾源培养菌根真菌，培养液中的钾浓度显著提高，故外生菌根真菌可促进土壤钾的溶解。在外生菌根真菌的培养液中，分别检测到苹果酸、丁二酸和柠檬酸，均检测到草酸和乙酸。Bo 07、Ld 03和Pt 715显著提高土壤交换性钾含量，Bo 07和Ld 03还显著降低矿物结构钾含量，说明外生菌根真菌不同程度地活化了土壤无效钾，分离自南方的菌株Bo 07、Ld 03和Pt 715总体上大于分离自北方的菌株Cg 04。此外，土壤矿物结构钾分别与总有机酸和草酸分泌量呈极显著负相关(r有机酸=－0.989＊＊，r草酸=－0.950* ，n=5)，与培养液pH 值呈显著正相关 (r =0.916*，n=5)，故外生菌根真菌分泌的氢离子和有机酸尤其是草酸可能活化土壤无效钾。【结论】供试外生菌根真菌能不同程度的活化土壤无效钾，其活化能力可能与分泌氢离子和有机酸尤其是草酸密切相关。

Abstract:

Abstract:［Objective］Ectomycorrhizal fungi (ECMF)，important components in forest ecosystems，could form symbionts with wooden plant roots and participate in nutrient absorption.［Methods］Boletnus sp.(Bo 07)，Lactarius delicious (Ld 03) and Pisolithus tinctorius (Pt 715) isolated from Southwest China and Cenococcum geophilum (Cg 04) from Daqing Mountain，Inn Mongolia，China，were cultured in liquid Pachlewsk medium at 25 1℃ for 28 days with soil as sole K source．Fungal biomass，K uptake，efflux of protons and organic acids，and changes of soil K pools were measured to study K mobilization from soil by ECMFs.［Results］The fungal biomass，K concentration and uptake of Bo 07，Ld 03 and Pt 715 were much higher than Cg 04，indicating their strong abilities to absorb K and to adapt low K environment by bio-evolution and selection．K concentrations in culture solution were increased by ECMFs compared to blank control (without ECMF)．ECMFs could promote K release from the soil into culture solution． Bo 07，Ld 03 and Pt 715 increased significantly exchangeable K in soils，while structural K in soil was decreased by Bo 07 and Ld 03．They could thus mobilize unavailable K from ［Conclusion］ECMF isolates could mobilize unavailable K in soils．