Figure 7
Levels of amino acids in maize plants in response to inorganic N sources. Concentration of the main amino acids in roots (A), xylem sap (B) and leaves (C) in maize plants grown for 10 days without N sources and then exposed for the last 30 h to absence of N (c, white bars), to 10 mM NO3 − (n, crossed white bars), to 10 mM NH4 + (a, grey bars) or to 5 mM NO3 − + 5 mM NH4 + (na, crossed and grey bars). Graphs show the amino acid concentrations (mM) as average values ± SE (roots and leaves n = 8, xylem sap n = 6). The letters above are assigned according to Student’s t-test (p ≤ 0.01; d p ≤ 0.05). Detailed quantification of individual amino acids in root, xylem and leaf is reported in Additional file 1: Table A8, A9 and A10, respectively.