Fig. 5.

Amino acids in nodules and in the xylem sap 3 weeks after beginning the application of an N₂/O₂ mixture (80/20; v/v) with either zero (–CO₂) or 2500 μl l⁻¹ CO₂ (+CO₂) to the root/nodule compartment. Data are the means of four replicates. Bars represent standard deviation. An asterisk indicates a statistically significant difference from the +CO₂ treatment (t test, P ≤0.05). (A) Concentrations of the five most abundant amino acids in the nodules. (B) Total amount in nodules per plant of the five most abundant nodule amino acids. In addition to the amino acids shown, Ala, Gaba, Tyr, Arg, Try, Lys, Val, Thr, Leu, His, Ile, Gly, and Prol. were detected in concentrations below 0.5 μmol g⁻¹ nodule fresh weight. (C) Concentrations of amino acids found in the xylem sap in concentrations above 0.1 μM.