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| Titel |
Reciprocal trade of Carbon and Nitrogen at the root-fungus interface in
ectomycorrhizal beech plants |
| VerfasserIn |
Christina Kaiser, Werner Mayerhofer, Marlies Dietrich, Stefan Gorka, Arno Schintlmeister, Siegfried Reipert, Peter Schweiger, Marieluise Weidinger, Julia Wiesenbauer, Victoria Martin, Andreas Richter, Dagmar Woebken |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250150651
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| Publikation (Nr.) |
 EGU/EGU2017-15133.pdf |
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| Zusammenfassung |
| Plants deliver recently assimilated carbon (C) to mycorrhizal fungi, and receive nutrients,
such as N and P, in exchange. A reciprocal exchange of C and nutrients between plants and
mycorrhizal fungi (i.e., fungi which deliver more nutrients receive more plant C in return and
vice versa) has been suggested for arbuscular mycorrhizal symbioses by some studies, but
challenged by others. For ectomycorrhizal associations even less is known on how the
exchange of C for nutrients is regulated, and whether it is based on reciprocity, or other
controls.
The aim of this study was to test the concept of reciprocal rewards between beech (Fagus
sylvatica) and their associated ectomycorrhizal fungi on different scales, namely (a) across
associations between individual root tips of beech and different fungal partners, and (b) at
the subcellular scale at the plant-fungus interface. We exposed young beech trees
associated with natural mycorrhizal fungal communities to a 13CO2 atmosphere
and added 15N-labelled amino acids to a ‘litter compartment’, that mycorrhizal
hyphae, but not plant roots could access. Plants were harvested within 2 days after
application of 15N and less than one day after applying 13CO2. If the trading of C for N
was reciprocal, we expect that 13C would be correlated to 15N across individual
plant-fungal connections and at the subcellular scale within one mycorrhizal root tip,
respectively.
We collected individual mycorrhizal root-tips from 8 plants right after harvest, analyzed
their 13C and 15N content by isotope-ratio mass spectrometry (EA-IRMS) and performed ITS
sequencing to identify fungal communities associated with individual root tips. Selected
mycorrhizal root tips were also prepared for nano-scale secondary ion mass spectrometry
(NanoSIMS) to visualize the spatial distribution of 13C and 15N in cross-sections of
mycorrhizal root-tips at the subcellular scale.
Our results showed a significant, albeit weak correlation between 13C and 15N across
collected mycorrhizal root-tips, the variability of which was seemingly influenced
by fungal colonization pattern. Within a cross-section of an individual root-tip,
however, NanoSIMS imaging revealed not only a high spatial heterogeneity of 13C and
15N across plant and fungal cells, but also a strong spatial correlation between 13C
and 15N in both, plant cells and fungal cells of the Hartig Net, the fungal mantle
and external hyphae. Intriguingly, individual ‘hotspots’ of external fungal hyphae
that were highly enriched in 15N (delivering high amounts of the added 15N to the
plant), were also always extraordinarily enriched in 13C (receiving more 13C in
return).
Our results provide first evidence for a reciprocal exchange of C for N between plants and
ectomycorrhizal fungi at the subcellular scale. This indicates that a mechanism at the cellular
level exists, that (i) either allows plants to direct their C flow into N-delivering parts of the
mycorrhizal hyphal network or (ii) allow the fungus to ‘draw’ more C from the plant (develop
a higher sink strength) when it has access to N. While such a mechanism still remains to be
elucidated, our study shows, for the first time, direct evidence for its existence. |
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