Arabidopsis amiR:ADC-L2 is a non-lethal line with several developmental defects, it is characterized by a drastic reduction in free polyamine content. Herein, we found that catalase application had growth promoting effects in amiR:ADC-L2 and parental Ws seedlings. Differences in ROS content between amiR:ADC-L2 and Ws seedlings were detected. Increased H2O2 levels were found in the amiR:ADC-L2, as well as low AtCAT2 gene expression and reduced catalase activity. Estimation of polyamine oxidase activity in amiR:ADC-L2 line indicated that the over-accumulation of H2O2 is independent of polyamine catabolism. However, increments in NADPH oxidase activity and Or content could be associated to the higher H2O2 levels in the amiR:ADC-L2 line. Our data suggest that low polyamine levels in Arabidopsis seedlings are responsible for the accumulation of ROS, by altering the activities of enzymes involved in ROS production and detoxification. (C) 2018 Elsevier Inc. All rights reserved.