Protective Antioxidant Enzyme Activities are Affected by Drought in Quinoa (Chenopodium Quinoa Willd)

Changes in water availability are responsible for a variety of biochemical stress responses in plant organisms. Stress induced by this factor may be associated with enhanced reactive oxygen species (ROS) generations, which cause oxidative damage. In the present study we investigated the activities of antioxidant enzymes superoxide dismutase (SOD), polyphenoloxydase (PPO), peroxidase (POD) and catalase (CAT), measured at flowering in quinoa, subjected to varying levels of drought stress. Drought levels were 100, 50 and 33% of evapotranspiration (ETc), and rainfed. Compared to full water supply (100%ETc), the activities of SOD under dry conditions (33%ETc) increased significantly by 39 and 90%, in 2011 and 2012, respectively. Under rainfed conditions, the activities of SOD increased by 178.71 and 322.42 %. The CAT activity in rainfed treatment increased significantly by 103.15% (2011) and 87.4% (2012) compared to the full water supply treatment. Compared to the control, POD activity in both essays increased significantly by 50.2% in 33%ETc of 2012 assay and increased by 72.8 and 115.6% in the rainfed treatment of 2011 and 2012 assays respectively. In comparison to the full watered treatment, the PPO activity increased in all treatments. These results suggest that antioxidant enzymes play important roles in reducing oxidative stress in quinoa plant exposed to drought stress. Keywords: Quinoa, water stress, deficit irrigation, biochemical responses, polyphenoloxydase (PPO), peroxidase (POD) and catalase (CAT)