BayCEER Workshop 2018

A widespread phenomenon to cheat on fungal partners? - New insights for partial mycoheterotrophy in arbuscular mycorrhizae -

P 6 in Open Poster Session

Introduction

Fungal root endophytes are either beneficial – represented by a bi-directional nutrient transfer between the plant and the fungus (mycorrhizas) – or antagonistic (mycoheterotrophy). Mycoheterotrophs exploit the fungi for carbon-nutrients. Stable isotope approaches are an elegant tool to unmask those cheaters.

For the globally distributed arbuscular mycorrhizae (AM, ~200.000 species) two types can be distinguished: Arum-type (after Arum maculatum) forming hyphae along cortical intercellular airspaces, Paris-type (after Paris quadrifolia) forming intracellular hyphal coils. So far, every achlorophyllous mycoheterotrophic AM plant species reveals the Paris-type, however green Paris-type species were rarely analyzed for mycoheterotrophy.

We aim to compare green plant species of the Arum- and Paris-type with the expectation that Paris-type species are enriched in ¹³C and ²H in analogy to hyphal coil forming mycoheterotrophs. 

Material and Methods

Arum maculatum, Paris quadrifolia and co-occurring plants as references were sampled in Germany (n = 50). Suitable stable isotope data sets (n = 490) of a literature review were in included to the analyses. Isotope-ratio mass spectrometry was applied to determine ¹³C, ²H and ¹⁸O of plant material.

Results

Paris quadrifolia and further Paris-type plants were significantly enriched in ¹³C and ²H compared to A. maculatum and further Arum-type plants. In most cases no differences were discovered for ¹⁸O.

Conclusions

For the first time, we showed that green arbuscular mycorrhizal Paris-type plant species are significantly enriched in ¹³C and ²H. It indicates that not only green orchids (~30.000 species) and few species from the ericoid plant family (~40 pyroloid species) digest their fungal partners for nutrient-gain but assumes the potential of half of all green AM plants for partial mycoheterotrophy (~100.000). Therefore, we may have to change our current view that ‘most mycorrhizas are beneficial for both partners’.

 

Keywords: Arum-type, Paris-type, mycoheterotrophy, stable isotope, carbon, nitrogen, hydrogen, oxygen