Partial mycoheterotrophy in Pyroleae: nitrogen and carbon stable isotope signatures during development from seedling to adult

• Published in: Oecologia 2015-01, Vol.177 (1), p.203-211
• Main Authors: Johansson, Veronika A, Mikusinska, Anna, Ekblad, Alf, Eriksson, Ove
• Format: Article
• Language: English
• Subjects: Adults; Autotrophic Processes; autotrophs; Biomedical and Life Sciences; Carbon - metabolism; Carbon Isotopes - metabolism; Chimaphila umbellata; Dust seeds; Ecology; Ericaceae; Ericaceae - growth & development; Ericaceae - metabolism; forests; Fungi - metabolism; Heterotrophic Processes; Hydrology/Water Resources; Hypopitys monotropa; interspecific variation; Isotopic enrichment; Life Sciences; Monotropa; Mycoheterotrophy; Mycorrhizae; Nitrogen; Nitrogen - metabolism; Nitrogen Isotopes - metabolism; nutrients; ontogeny; Orchidaceae; Orthilia secunda; Photosynthesis; PHYSIOLOGICAL ECOLOGY; Physiological ecology - Original research; Plant Development; Plant Ecology; Plant Sciences; Pyrola chlorantha; Pyrola minor; Seedlings; Seeds - chemistry; Stable isotopes; Subterranean seedlings; Sweden; symbiosis; växtekologi
• ISSN: 0029-8549; 1432-1939; 1432-1939
• DOI: 10.1007/s00442-014-3137-x

Mycoheterotrophic plants (MHP) are divided into non-photosynthesizing full MHP and green-leaved partial or initial MHP. We investigated¹³C and¹⁵N isotope enrichment in five putatively partial MHP species in the tribe Pyroleae (Ericaceae): Chimaphila umbellata, Moneses uniflora, Orthilia secunda, Pyrola chlorantha and Pyrola minor, sampled from forest sites on Öland, Sweden. For M. uniflora and P. chlorantha, we investigated isotope signatures of subterranean seedlings (which are mycoheterotrophic), to examine how the use of seedlings instead of full MHP species (Hypopitys monotropa) as reference species affects the assessment of partial mycoheterotrophy. Our main findings were as follows: (1) All investigated Pyroleae species were enriched in¹⁵N compared to autotrophic reference plants. (2) significant fungal-derived C among the Pyroleae species was found for O. secunda and P. chlorantha. For the remaining species of C. umbellata, M. uniflora and P. minor, isotope signatures suggested adult autotrophy. (3) C and N gains, calculated using seedlings as a full MHP reference, yielded qualitatively similar results as when using H. monotropa as a reference. However, the estimated differences in C and N gains became larger when using seedlings as an MHP reference. (4) A previously unknown interspecific variation in isotope signature occurs during early ontogeny, from seed production to developing seedlings. Our findings suggest that there is a variation among Pyroleae species concerning partial mycoheterotrophy in adults. Adult autotrophy may be most common in Pyroleae species, and these species may not be as dependent on fungal-derived nutrients as some green orchids.