Fig. 5. Transfer rates of ¹⁵N-labelled nitrogen applied to the labelling compartment in the form of chitin to the roots (grey bars) or to the mycorrhizal hyphae in the root-free zone of the large Petri dish (black bars) in Experiment 2.

Results are shown separately for non-mycorrhizal plates without protists (A), non-mycorrhizal plates with protists (B), mycorrhizal plates without protists (C), and mycorrhizal plates with protists (D). Shown are mean values (and standard deviations) of 4–7 replicates per bacterial treatment. Different lower-case letters in each graph indicate significant differences between treatment means within the individual graphs. The numbers presented are percentages of ¹⁵N-labelled nitrogen applied as chitin into the labelling compartment, and recovered outside the labelling compartment either in the roots or in the mycorrhizal hyphae. Means were separated by Duncan’s post-hoc test (p < 0.05), following significant ANOVAs (respective F values and p value ranges are shown for each individual graph). Data were log(x + 0.1) transformed prior to ANOVA. Statistical comparisons were carried out separately for each of the four scenarios (i.e. presence or absence of the mycorrhizal fungus and presence or absence of the protist). *** p < 0.001, ** 0.01 > p ≥ 0.001.