The use of multi-element stable isotope natural abundance (d13C, d15N, d2H) to elucidate orchid mycorrhizal nutrition

Titelangaben

Gebauer, Gerhard ; Schweiger, Julienne:
The use of multi-element stable isotope natural abundance (d13C, d15N, d2H) to elucidate orchid mycorrhizal nutrition.
2021
Veranstaltung: 2021 Virtual World Orchid Conference , 23.-26. April 2021 , Taichung, Taiwan.
(Veranstaltungsbeitrag: Kongress/Konferenz/Symposium/Tagung , Paper )

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Abstract

Orchid mycorrhiza is the most intimate interaction between plants and fungi. The usually mutualistic mycorrhiza is not only subverted by all orchids in the early seedling development stage, but also by many orchid species that remain achlorophyllous and thus, fully mycoheterotrophic throughout their entire life cycle. Initially and fully mycoheterotrophic orchids are completely supported by their mycorrhizal fungi and thus, get enriched in heavy isotopes of the elements carbon and nitrogen. Stable isotope natural abundance has been instrumental to identify also mycoheterotrophic carbon gains by adult chlorophyllous orchids in addition to simultaneous carbon gain from their own photosynthesis. This nutritional mode is now known as partial mycoheterotrophy. Until recently, partially mycoheterotrophic orchids in analogy to the majority of fully mycoheterotrophic orchids have been assumed to be exclusively mycorrhizal with fungi simultaneously forming ectomycorrhizas with forest trees and to be growing under light-limited conditions of forest grounds. By adding hydrogen stable isotope abundance to the more frequently used carbon and nitrogen stable isotope abundance, we demonstrate here that also many orchid species exclusively mycorrhizal with saprotrophic rhizoctonia fungi – and this is the vast majority of all orchids – gain organic carbon from their fungal partner and are therefore also partially mycoheterotrophic. Partial mycoheterotrophy among rhizoctonia-mycorrhizal orchids is not only limited to forest-ground orchids, but also frequently distributed among orchids growing on full sunlight meadows. Thus, partial mycoheterotrophy is much more distributed among orchids than previously assumed.