Fig. 2.

Net fluxes of NH₄ ⁺ (A), NO₃ ^– (B), and H⁺ (C) in 10min at 15mm from the root apex of fine roots of P. popularis (Pp) and P. alba × P. glandulosa (Pg). Data indicate mean ± SE (n = 6). The measuring solution (pH 5.5) contained 0.1mM KCl and 0.1mM CaCl₂ as well as 10, 100, or 1000 μM NH₄NO₃. Bars labelled with different letters indicate significant difference between the treatments. P-values of the ANOVAs of species, N treatment, and their interaction are indicated. *P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001; ns, not significant (this figure is available in colour at JXB online).