Temperature-respiration relationships differ in mycorrhizal and non-mycorrhizal root systems of Picea abies (L.) Karst.

Root respiration has been shown to increase with temperature, but less is known about how this relationship is affected by the fungal partner in mycorrhizal root systems. In order to test respiratory temperature dependence, in particular Q(10) of mycorrhizal and non-mycorrhizal root systems, seedlings of Picea abies (L.) Karst. (Norway spruce) were inoculated with the ectomycorrhizal fungus Piloderma croceum (Eriksson and Hjortstam, SR430; synonym: Piloderma fallax: [Libert] Stalpers) and planted in soil respiration cuvettes (mycocosms). Temperature dependence of hyphal respiration in sterile cultures was determined and compared with respiration of mycorrhizal roots. Respiration rates of mycorrhizal and non-mycorrhizal root systems as well as sterile cultures were sensitive to temperature. Q(10) of mycorrhizal root systems of 3.0 +/- 0.1 was significantly higher than that of non-mycorrhizal systems (2.5 +/- 0.2). Q(10) of P. croceum in sterile cultures (older than 2 months) was similar to that of mycorrhizal root systems, suggesting that mycorrhizae may have a large influence on the temperature sensitivity of roots in spite of their small biomass. Our results stress the importance of considering mycorrhization when modeling the temperature sensitivity of spruce roots.