Interaction of soil filamentous fungi affects needle composition and nutrition of Norway spruce seedlings

The effects of the interactions of soil filamentous fungi (including saprotrophic, mycorrhizal and endophytic fungi) on several morphological and physiological parameters of Norway spruce seedlings [Picea abies (L.) Karst.] were studied in a pot experiment. Both mycorrhizal variants (Hebeloma bryogenes and Cadophora finlandica) were slightly inhibited with respect to the accumulation of aboveground biomass. However, these variants exhibited significantly improved foliar content of N, P, and Ca (H. bryogenes variant also K), compared to controls. The presence of the saprotrophic fungus Setulipes androsaceus attenuated the positive effect of mycorrhizal fungi on Ca, P, and K content, but did not reduce the positive effect of mycorrhizal fungi on the N content of the seedlings' needles. Raman spectroscopy revealed that both mycorrhizal fungi increased the foliar content of carotenoids compared to the controls, but the effect diminished in the presence of S. androsaceus. In contrast, in the presence of the dark septate endophyte Phialocephala fortinii, needles exhibited significantly higher wax content and lower carotenoid content compared to the mycorrhizal variants. The presence of the saprotrophic isolate Serpula himantoides resulted in a decrease in needle waxes in comparison to controls. The needles' carotenoid concentration was positively correlated with the levels of needle nutrients (N, P, K, Ca, Mg), while correlation of needle nutrients (N, P) with the needle wax concentration was negative. We conclude that not only individual fungi but also their interactions profoundly affect the nutrition and needle composition of Norway spruce seedlings.