Mixotrophic species obtain their carbon by mixing autotrophy and heterotrophy. Some forest mixotrophs gain their energy and carbon from both photosynthesis and mycorrhizal fungi colonizing their roots; the plasticity of orchids increasing their use of fungal carbon in young shoots (before leaf expansion) and in shaded conditions has been well studied.
Lallemand et al. investigate developmental and environmental plasticity of mixotrophy in pyroloids (Pyroleae, Ericaceae) by measuring leaf isotopic abundance and nitrogen content in temperate Boreal forests. The absence of noticeable responses to age or light availability in pyroloids, in contrast to co-occurring orchids, suggests unexpected diversity of mixotrophic nutrition strategies.
Lallemand, F., Puttsepp, Ü., Lang, M., Luud, A., Courty, P.-E., Palancade, C., & Selosse, M.-A. (2017). Mixotrophy in Pyroleae (Ericaceae) from Estonian boreal forests does not vary with light or tissue age. Annals of Botany, 120(3), 361–371. https://doi.org/10.1093/aob/mcx054