Figure 2

The contents of phenolic acids in the root secretions of P. heterophylla as analyzed with HPLC.
1: p-hydroxybenzoic acid, the retention time was 5.196 min; 2: vanillic acid, the retention time was 5.771 min; 3: syringic acid, the retention time was 6.386 min; 4: vanillin, the retention time was 7.677 min; 5: ferulic acid, the retention time was 8.433 min; 6: benzoic acid, the retention time was 12.318 min; 7: salicylic acid, retention time was 14.56 min; 8: cinnamic acid, the retention time was 19.624 min.