Figure Legends
Fig.1: Stoichiometric responses in fungal C:N:P ratios to varying N and P supply in defined glucose media. a, b and c depict shifts in fungal C:N, C:P and N:P ratios in response to varying media supply ratios (axes are log10 transformed). Lines represent the linear response of fungal stoichiometry, symbols data points of individual isolates (see legend). Line colors depict 1/H values calculated for each fungal isolate, with maximum and minimum values shown in the respective color legend.
Fig. 2: Fungal stoichiometric responses to nitrogen (N), phosphorus (P), cellulose (Cel) and glucose (Glu) manipulations in soil extract agar. Fungal C:N (a ), C:P (b ) and N:P (c ) values are illustrated as violin plots, a mirrored density plot showing overall data distribution, with average values illustrated by dots (8 (a ) or 4 (b,c ) isolates, 3 repetitions each). Letters indicate deviations among treatments (linear mixed-effects model), red dots deviations from control values (P < 0.05). Large variations are mainly driven by distinct differences among isolates (see Fig. S6).
Fig. 3: Correlations of total fungal (a ) carbon (C), (b ) nitrogen (N) and (c ) phosphorus (P) mass [mg] with fungal biomass [mg] in different nutrient manipulation experiments (both standardized [0,1] for comparisons among elements and fungal isolates). Lines show predicted model outputs from linear mixed effects models, with grey areas illustrating 95% confidence intervals. Line types indicate respective nutrient manipulation experiments (solid: N manipulation in glucose medium; dashed: P manipulation in glucose medium; dotdashed: N manipulation in cellulose medium; longdashed: fertilization experiment in soil extract agar). For correlations conducted in each medium respective formulas of regression lines as well as R² values are given. Pie charts illustrate the relative variation in element masses determined by fungal biomass (dark grey) versus the respective nutrient manipulation treatments applied (light blue). 3D correlation graphs (d-e ) further illustrate the relative contribution of fungal biomass versus nutrient manipulation to total element mass, exemplarily shown for N manipulations in defined glucose media.
Fig. 4: Positive correlations of relative fungal nitrogen (N) and phosphorus (P) concentrations [% deviation from maximum values] in defined glucose media (a, d ), soil-extract agar (b,e ) and defined cellulose medium (c ). The relative deviation of fungal concentrations of the manipulated element is depicted on the x-axis, while the relative concentrations of the respective other element (unchanged in media) is plotted on the y-axis. The chosen relative values allow to assess effect sizes in element reductions, and reduce isolate-specific variability by data standardization. Colors and symbols depict respective treatments applied (see legends), black lines predicted model outputs from linear mixed effects models, with grey areas illustrating 95% confidence intervals (*** P < 0.001).
Fig. 5: Spatial and temporal shifts in fungal C:N ratios are depicted, with colors illustrating fungal nitrogen concentrations (red: high, grey: low). Stoichiometry was compared in (a ) inner versus outer parts of the mycelium (4 fungal isolates, 3 repetitions each), and in fungi grown for 12 or 26 days (b ) on soil-extract agar (12 fungal isolates, 3 repetitions each), as well as in (c ) inner versus outer parts of mycelium grown in glucose media with low (C:N = 200) and high (C:N = 20) N supply (4 fungal isolates, 3 repetitions each). (a, b ) Dots represent data points underlain by box-and-whisker plots. P -values are based on paired t-tests. Illustrations depict potential element distributions in fungal mycelia (see Fig. 6). (c ) Bars illustrate mean values of fungal C:N ratios measured in inner (hatched bars) and outer (filled bars) parts of the fungal mycelium. Tested fungal isolates differ in 1/HCN values, previously determined along a larger gradient of C:N (see Fig. 1). Given P -values are based on three-way type III analyses of variances.
Fig. 6: Illustration of potential mechanisms in fungal mycelia allowing flexible carbon:nutrient (C:X) adjustments to nutrient limited conditions. Colors indicate element contents throughout different mycelial parts (red: low C:X, i.e. high nutrient contents; grey: wide C:X, i.e. low nutrient contents). Little grey dots illustrate the distribution of C throughout mycelia, red dots nutrients, e.g. nitrogen and phosphorus. Mycelial growth form depicts typical adaptations to reduced nutrient supply (decreased biomass, density and activity (Fig. S2; Camenzind et al. 2020)).