Effect of NaCl Stress on Antioxidant Enzyme Activities and Isoenzyme Pattern of Broussonetia papyrifera Plantlets

The activities and isoforms of superoxide dismutase peroxidase (POD) and catalase (CAT), as well as the contents of proline, soluble protein (SOD) and malondialdehyde (MDA) in plantlets of Broussonetia papyrifera subjected to salt stress treatments of 50, 75, 100, 125 and 150 mmol•L^(-1) NaCl were studied. Our results demonstrated that soluble protein content increased with NaCl concentration at low level of NaCl concentration, and it decreased when NaCl concentration exceeds 100 mmol•L^(-1). SOD activity showed a slight decrease in low concentration of NaCl and then an increase with further increase in NaCl concentration. Moreover, the isoforms of SOD were affected by salt stress. POD exhibited a similar trend in enzyme activity as compared to SOD, However, the POD isoforms were minimally affected by NaCl treatment. CAT activity was increased by salt treatment. Moreover, proline contents markedly increased while the contents of MDA was increased at first and decreased subsequently in response to salt stress.