Journal of Plant Ecology Advance Access originally published online on August 18, 2009
Journal of Plant Ecology 2009 2(3):107-118; doi:10.1093/jpe/rtp015
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Use of 15N stable isotope to quantify nitrogen transfer between mycorrhizal plants
1 School of Life Sciences, Yunnan Normal University, Kunming, Yunnan 650092, China
2 School of Plant Biology (M084), University of Western Australia, Crawley, Western Australia 6009, Australia
3 Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing 100081, China
4 Key Laboratory for Environmental and Urban Sciences, Shenzhen Graduate School, Peking University, Shenzhen 518055, China
5 State Key Laboratory of Earth Surface Processes and Resource Ecology, Beijing Normal University, Beijing 100875, China
6 College of Resource and Environmental Sciences, Northwest A&F University, Yangling, Shaanxi 712100, China
* Correspondence address. School of Plant Biology, University of Western Australia, Crawley, WA 6009 Australia. Tel: +61-864882231; Fax: 61-864881108; E-mail: xinhua5658{at}hotmail.com
Aims: Mycorrhizas (fungal roots) play vital roles in plant nutrient acquisition, performance and productivity in terrestrial ecosystems. Arbuscular mycorrhizas (AM) and ectomycorrhizas (EM) are mostly important since soil nutrients, including NH
, NO
and phosphorus, are translocated from mycorrhizal fungi to plants. Individual species, genera and even families of plants could be interconnected by mycorrhizal mycelia to form common mycorrhizal networks (CMNs). The function of CMNs is to provide pathways for movement or transfer of nutrients from one plant to another. In the past four decades, both 15N external labeling or enrichment (usually expressed as atom%) and 15N naturally occurring abundance (
15N, 
) techniques have been employed to trace the direction and magnitude of N transfer between plants, with their own advantages and limitations.
Important Findings: The heavier stable isotope 15N is discriminated against 14N during biochemical, biogeochemical and physiological processes, due to a greater atomic mass. In general, non-N2-fixing plants had greater 15N values than N2-fixing (
0) ones. Foliar 15N often varied by 5 to 10 in the order: non-mycorrhizas/AMs > EMs 
ericoid mycorrhizas. Differences in 15N () or 15N (atom%) values could thus provide N transfer information between plants. A range of between 0 to 80% of one-way N transfer had been observed from N2-fixing mycorrhizal to non-N2-fixing mycorrhizal plants, but generally less than or around 10% in the reverse direction. Plant-to-plant N transfer may provide practical implications for plant performance in N-limited habitats. Considering that N translocation or cycling is crucial, and the potential benefits of N transfer are great in both agricultural and natural ecosystems, more research is warranted on either one-way or two-way N transfers mediated by CMNs with different species and under field conditions.
Keywords: 15N enrichment • 15N natural abundance (15N) • 15N stable isotope • common mycorrhizal networks (CMNs) • nitrogen transfer