A methodological approach to improve estimates of nutrient gains by partially myco-heterotrophic plants†

†Revised version of a paper presented at the 30th Annual Meeting of the German Association for Stable Isotope Research (GASIR), 8–10 October 2007, Bayreuth, Germany.

Abstract

The stable isotopes ¹⁵N and ¹³C can be used to investigate the nutritional mode of terrestrial orchids and pyroloids (Monotropoideae, Ericaceae). Some of these plants are putatively autotrophic but meet their nitrogen and carbon demands by gaining organic compounds (e.g. amino acids) from mycorrhizal fungi. This so-called partially myco-heterotrophic nutrition is reflected by their isotope signature. The application of a two-source linear mixing model on δ values of such plants allows calculating the percentage of N and C derived from their associated mycorrhizal fungi. Here we present an approach to improve estimates of the plants’ degree of myco-heterotrophy. Due to the presented conversion of δ values into enrichment factors (ϵ), results obtain a better resolution and data from various studies become normalised which facilitates combined representations and meta-analyses.

†Revised version of a paper presented at the 30th Annual Meeting of the German Association for Stable Isotope Research (GASIR), 8–10 October 2007, Bayreuth, Germany.

Keywords:

• carbon-13
• enrichment factor
• Ericaceae
• linear mixing model
• method
• myco-heterotrophy
• natural isotope abundance
• nitrogen-15
• Orchidaceae

Acknowledgements

This methodological study contributes to the DFG project GE 565/7-1. We are grateful for valuable discussions with Nicole A. Hynson (University of California, Berkeley) on the overall mean enrichment factor.

Notes

†Revised version of a paper presented at the 30th Annual Meeting of the German Association for Stable Isotope Research (GASIR), 8–10 October 2007, Bayreuth, Germany.