Fig. 2

Concentration and molar ratios of elements in groups of orchids representing different tropic modes. average (horizontal bar), quartiles (box) and value range (whiskers) for carbon (C), nitrogen (N), phosphorus (P) concentration, and ratio of the elements, autotrophy (AT), mixotrophy (MX), mycoheterotrophy (MH), and reference autotrophic non-orchid species (REF). The letters above the bottom line indicate the significant differences at p < 0.05 based on the post-hoc Games-Howell test after Welch ANOVA showed significant differences between groups for both nutrient concentration and their proportions ( C - F = 4,17, df = 3, p = 0.01; .N - F = 42.9, df = 3, p < 0.001; P - F = 67.3, df = 3, p < 0.001; C:N - F = 35.8, df 3; p < 0.001; C:P - F = 58.3, df = 3, p < 0.001; N:P - F = 34.3, df = 3, p < 0.001). Values for C, N and P concentration are given in mg/g DM