Figure 4. HPLC chromatograms of adenosine standard, samples of the root under ambient [CO₂] and elevated [CO₂].

Peak #1 is adenosine commercial standard. A: Representative chromatogram for adenosine standard (The contents of adenosine were 0.0272 mg/ml. Five concentrations of adenosine standard have been measured for the standard curve: 0.0068, 0.0136, 0.0272, 0.0544 and 0.068 mg/ml). B: Root sample chromatogram under ambient [CO₂](one out of three replicates). C: Root sample chromatogram under elevated [CO₂] (one out of three replicates).