As shown for exudated POD, the presence of sludge has also increased plants’ wall-bound POD activity (p = 0.06). Though the wall-bound POD activity of P. australis did not vary according to the season, the specific activity doubled in spring compared to summer. Spring is a season of high metabolism activity for growth and since POD also plays a role in lignin polymerization ( Almagro et al., 2009), its increase in spring is possibly linked to this phenomenon.