Nitrogen isotope fractionation during N uptake via arbuscular mycorrhizal and ectomycorrhizal fungi into grey alder

作者：Schweiger Peter F^*

来源：Journal of Plant Physiology, 2016, 205: 84-92.

DOI：10.1016/j.jplph.2016.08.004

• delta N-15
• Alnus incana (grey alder)
• Arbuscular mycorrhiza
• Ectomycorrhiza
• Isotope fractionation
• Nitrogen uptake

Arbuscular mycorrhizal (AM) and ectomycorrhizal (ECM) fungi affect plant nitrogen (N) dynamics. Plant N isotope patterns have been used to characterise the contribution of ECM fungi to plant N uptake. By quantifying and comparing the effects of an AM and an ECM fungus on growth, N uptake and isotopic composition of one host plant grown at different relative N supply levels, the aim of this study was to improve the mechanistic understanding of natural N-15 abundance patterns in mycorrhizal plants and their underlying causes.
Grey alders were inoculated with one ECM fungus or one AM fungus or left non-mycorrhizal. Plants were grown under semi-hydroponic conditions and were supplied with three rates of relative N supply ranging from deficient to luxurious.
Neither mycorrhizal fungus increased plant growth or N uptake. AM root colonisation had no effect on whole plant delta N-15 and decreased foliar delta N-15 only under N deficiency. The roots of these plants were N-15-enriched. ECM root colonisation consistently decreased foliar and whole plant delta N-15.
It is concluded, that both mycorrhizal fungi contributed to plant N uptake into the shoot. Nitrogen isotope fractionation during N assimilation and transformations in fungal mycelia is suggested to have resulted in plants receiving N-15-depleted N via the mycorrhizal uptake pathways. Negative mycorrhizal growth effects are explained by symbiotic resource trade on carbon and N and decreased direct plant N uptake.

• 出版日期2016-10-20