Contrasting effects of indigenous arbuscular mycorrhizal fungi on nitrogen absorption of C3 and C4 grasses: Evidence from microcosm and 15N labeling experiments

Background and aims
Nitrogen (N) captured by arbuscular mycorrhizal (AM) symbiosis is a major pathway in the N uptake of host plants.  However, the relative contribution of arbuscular mycorrhizal fungi (AMF) to N uptake in different plant functional types has not been well assessed.
Methods
Two dominant plant species in semiarid steppe ecosystems on the Mongolian plateau, i.e. Leymus chinensis (C3 grass) and Cleistogenes squarrosa (C4 grass), were selected in this study.  We conducted a greenhouse manipulation experiment using novel microcosms combined with 15N labeling techniques and investigated the effect of indigenous AMF on plant growth and quantified their relative contribution to N uptake under high and low levels of available soil N. 
Results
Indigenous AMF contribute more to N uptake in C3 grass than that in C4 grass, and mycorrhizal partners act as parasites for C4 plant growth.  For L. chinensis, indigenous AM symbiosis suppressed plant growth under low soil N but improved pl...

研究背景与研究目的
丛枝菌根共生体（arbuscular mycorrhizal symbiosis，AM）所捕获的氮素，是宿主植物氮吸收的关键途径之一。然而，丛枝菌根真菌（arbuscular mycorrhizal fungi，AMF）对不同植物功能型宿主氮吸收的相对贡献尚未得到充分评估。
研究方法
本研究选取蒙古高原半干旱草原生态系统中的两种优势植物物种，即羊草（C3草本植物）与糙隐子草（C4草本植物）。本研究采用新型微宇宙培养体系结合15N标记技术开展温室控制实验，探究土著丛枝菌根真菌（AMF）对植物生长的影响，并定量分析高低土壤有效氮水平下，其对植物氮吸收的相对贡献。
研究结果
土著丛枝菌根真菌（AMF）对C3草本植物氮吸收的贡献高于C4草本；菌根共生体对C4植物的生长反而起到寄生作用。对于羊草而言，土著丛枝菌根共生体在低土壤有效氮条件下会抑制植物生长，但可促进……