Drought stress is a crucial factor that affects plant growth and development. Reposition of reactive oxygen species (ROS) is one of the biochemical changes happening when plants are exposed to stress. Plants use enzymatic antioxidant defense mechanisms to remove ROS. In the current study, variations of antioxidant enzymes were measured in leaves and stolons of licorice plants (Glycyrrhiza glabra) growing under normal and drought conditions. Samples were harvested at 2, 16, 26 and 28 days after drought imposition treatment. These samples assigned to three drought treatments, without stress (S2), moderate stress (S16) and severe stress (S26 and S28). In comparison with control samples, superoxide dismutase (SOD), ascorbate peroxidase (APX) and peroxidase (POD) activities were up regulated by moderate and severe drought stress in leaves and stolons. The maximum activities of these enzymes were detected in severe stress. Catalase (CAT) and glutathione reductase (GR) activities were decreased in all stressed samples. The increased activities of SOD, APX and POD in severe stress indicated the important role of these enzymes in protecting licorice plants against oxidative stress.
