Transfer of 13C between paired Douglas-fir seedlings reveals plant kinship effects and uptake of exudates by ectomycorrhizas

• Published in: The New phytologist Vol. 214; no. 1; pp. 400 - 411
• Main Authors: Pickles, Brian J., Wilhelm, Roland, Asay, Amanda K., Hahn, Aria S., Simard, Suzanne W., Mohn, William W.
• Format: Journal Article
• Language: English
• Published: Lancaster New Phytologist Trust 01.04.2017; Wiley Subscription Services, Inc
• Subjects: carbon (C) allocation; ectomycorrhizas; host relatedness; interior Douglas‐fir; phospholipid fatty acid (PLFA); stable‐isotope probing
• ISSN: 0028-646X; 1469-8137
• DOI: 10.1111/nph.14325

Processes governing the fixation, partitioning, and mineralization of carbon in soils are under increasing scrutiny as we develop a more comprehensive understanding of global carbon cycling. Here we examined fixation by Douglas-fir seedlings and transfer to associated ectomycorrhizal fungi, soil microbes, and full-sibling or nonsibling neighbouring seedlings. Stable isotope probing with 99% 13C-CO2 was applied to trace 13C-labelled photosynthate throughout plants, fungi, and soil microbes in an experiment designed to assess the effect of relatedness on 13C transfer between plant pairs. The fixation and transfer of the 13C label to plant, fungal, and soil microbial tissue was examined in biomass and phospholipid fatty acids. After a 6 d chase period, c. 26.8% of the 13C remaining in the system was translocated below ground. Enrichment was proportionally greatest in ectomycorrhizal biomass. The presence of mesh barriers (0.5 or 35 lm) between seedlings did not restrict 13C transfer. Fungi were the primary recipients of 13C-labelled photosynthate throughout the system, representing 60–70% of total 13C-enriched phospholipids. Full-sibling pairs exhibited significantly greater 13C transfer to recipient roots in two of four Douglas-fir families, representing three- and fourfold increases (+ c. 4 lg excess 13C) compared with nonsibling pairs. The existence of a root/mycorrhizal exudation–hyphal uptake pathway was supported.