Poplars are widely utilized in the intensive and biomass production, as well as in breeding and environment protection programmes. This experiment was performed to investigate the effect of drought stress on poplar clones (M-1, PE19/66 and B-229). Poplar clones were grown hydroponically under controlled conditions and exposed to drought stress by applying polyethylene glycol (PEG) 6000. The plant samples were collected and separated into roots and leaves. For estimation of antioxidant status, activities of different antioxidant enzymes were determined (superoxide dismutase (SOD), catalase (CAT), guaiacol peroxidase (POD), glutathione peroxidase (GPX), glutathione reductase (GR) and ascorbate peroxidase (APX)), as well as antiradical power (ARP) against hydroxyl ( ̇OH) radical using ESR spin-trapping. The water stress parameters like proline (PRO) content, activity of proline dehydrogenase (PDH) and glycine betaine (GB) content were determined. Drought stress had significant effects on PRO and GB contents, SOD, APX and CAT activities when compared to control. All investigated extracts were determined as good inhibitors for ̇OH radical reduction, especially clone M-1where there was an increase of ARP against ̇OH radical in drought condition what could help to prevent or meliorate oxidative damage. Results indicated that the M-1 clone had a greater accumulation of substances for osmotic adjustment and a more efficient enzymatic detoxification cycle for eliminating the negative effects caused by ROS under drought stress than clones B-229 and PE19/66. This study provides valuable information for understanding drought-responsive mechanisms in leaves and roots of poplar clones M-1, B-229 and PE19/66.

Keywords: antioxidant enzymes, climate change, drought, glycine betaine, proline