Spatial distribution of nitrogen recently taken up by the fungal symbiont in an ectomycorrhizal root tip of Fagus sylvatica visualized by NanoSIMS.


Recently photoassimilated carbon and fungus-delivered nitrogen are spatially correlated in the ectomycorrhizal tissue of Fagus sylvatica.
Ectomycorrhizal plants trade plant-assimilated carbon for soil nutrients with their fungal partners. The underlying mechanisms, however, are not fully understood. In this paper the authors investigate the exchange of carbon for nitrogen in the ectomycorrhizal symbiosis of Fagus sylvatica across different spatial scales from the root system to the cellular level. They provide 15N-labelled nitrogen to mycorrhizal hyphae associated with one half of the root system of young beech trees, while exposing plants to a 13CO2 atmosphere and analysed the short-term distribution of 13C and 15N in the root system with isotope-ratio mass spectrometry, and NanoSIMS. The results show that, on a coarse scale, plants do not allocate a larger proportion of photoassimilated C to root parts associated with N-delivering ectomycorrhizal fungi. Within the ectomycorrhizal tissue, however, recently plant-assimilated C and fungus-delivered N were spatially strongly coupled.

Mayerhofer et al., 2021, New Phytologist 232: 2457–2474