Poplar and diclofenac pollution: A focus on physiology, oxidative stress and uptake in plant organs

Poplar plants may have an important role in the removal of pharmaceuticals from contaminated waters. In this context, plant uptake of the non-steroidal anti-inflammatory drug diclofenac, as well as physiological response in terms of growth traits and stress enzymes activity was assessed in Populus alba Villafranca clone, in order to establish the effectiveness of this species against pharmaceutical active compounds pollution. This evaluation was conducted in mesocosms with 1 mg L⁻¹ of this pharmaceutical for a maximum period of 28 days. Root appears to be the organ with clear uptake of diclofenac (14.76 ± 2.42 ng g⁻¹ fresh weight after 1 day of treatment), and presence of products derived from its metabolism. Indeed, 4-OH-diclofenac metabolite was detected in root tissues, indicating diclofenac uptake and metabolism inside the plants, already after 1 day of treatment. Regarding enzyme activities, glutathione-S-transferases increased in roots after long-term exposure to diclofenac, while an increase in activity of ascorbate peroxidase and glutathione reductase was detected in short and medium-term exposure, as a result of abiotic stress caused by diclofenac. Results suggest the ability of poplar to actively participate in the removal of diclofenac from water when used for phytoremediation purpose.