Regarding the cell wall compartment, the ionically bound POD activity of the plants was lower than the exudated POD. However, they may play a role in detoxication as they have been shown to be involved in oxidation of phenolic compounds (Sukalovic et al., 2005). Similarly to exudated POD, the wall-bound POD activity of P. australis (alone or in mixture with T.latifolia) was higher than that of the other species during the three seasons ( Fig. 2), especially in winter, it was 0.6 U/g root DW, while the recorded activity was about 0.2 U/g root DW from I. pseudacorus and T. latifolia (p = 0.0003). In addition, the specific POD activity ( Table 1) of P. australis was between 50 and 600 U/g protein while for the others it was always below 200 U/g protein or even undetectable.