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Root anatomical adaptations of contrasting ectomycorrhizal exploration types in Pinus sylvestris and Quercus petraea across soil horizons
Abstract Aims The anatomical characteristics of ectomycorrhizal exploration types in response to soil variability remain insufficiently understood. We examined the root anatomy of contact and long-distance exploration types in Pinus sylvestris and Quercus petraea, species with distinct ecological needs, across different soil horizons. Methods The diameter of ectomycorrhizal roots, the root absorptive traits i.e. proportion of cortex and mantle area, the percentage stele in the diameter, and the weighted average diameter of vessels (Ra) in the ectomycorrhizas were measured within ectomycorrhizas collected from organic and mineral soils across the soil profile. Results The absorptive traits varied along soil horizons, in which water and nutrient availability changed inversely. The proportion of cortex was associated with exploration type, but was not specific to tree species. However, the ectomycorrhizal diameter and the percentage of mantle within the root forming contact exploration type of P. sylvestris showed no variation among soil horizons. In contrast, the soil horizon significantly influenced all root anatomical traits in the contact exploration type of Q. petraea by enhancing the contribution of the absorption area of the root area, mainly in the illuvial horizon, but reaching the smallest value in the organic horizon. The Ra and the cell wall thickness of the vessels were strongly dependent on tree species. With increasing soil depth, Ra in Q. petraea increased, and stele proportion in root diameter decreased. Conclusion The results suggest that water acquisition traits differ among tree species, but traits associated with nutrient absorption (proportion of cortex and mantle area) within specific soil horizons are closely related to the ectomycorrhizal exploration type.
Low Temperature Enhances N-Metabolism in Paxillus involutus Mycelia In Vitro: Evidence From an Untargeted Metabolomic Study
ABSTRACTThis metabolomic study investigates, using GC MS/MS analysis, the molecular response of Paxillus involutus mycelia to prolonged low temperature (4°C) exposure. Alongside reduced growth, decreased overall nutrient levels, and increased oxidative stress indicators, analyses revealed a significant increase in nitrogen (N) concentration and enhanced N metabolism, particularly via the GS–GOGAT pathway, which was associated with elevated concentrations of numerous amino acids. In contrast, carbon (C) metabolism was not intensified but largely reprogrammed, with varying changes in carbohydrate abundance but higher levels of several stress‐related metabolites, such as trehalose and inositol family members, indicating activation of tolerance mechanisms, all with unchanged C (%). These changes suggest enhanced NH4+ uptake and a redirection of glycolysis‐derived C skeletons towards N‐compound biosynthesis. The lack of massive upregulation of typical anti‐stress compounds under low temperature exposure indicates either acclimatisation or mild stress. Mycelial restructuring, including increased dry mass (%) and accumulation of chitin precursors, implies cell wall remodelling and cold acclimatisation, supported by changes in membrane components. All these findings suggest that low temperatures may enhance N metabolism in ECM fungi even without additional carbon supply, potentially affecting symbiotic balance under climate change. Further studies are needed to validate these mechanisms and ecological implications.