Effect of short- and long-term salinity on the activities of antioxidative enzymes and lipid peroxidation in tomato roots

Changes in the antioxidative enzyme activities (SOD, CuZnSOD, GSH-Px, GST), as well as TBARS content in 5-week-old tomato (Lycopersicon esculentum Mill. cv "Perkoz") roots were examined 1, 3 h (short-term stress) and 1-14 days (long-term stress) after a single application of 50 mM (mild stress) and 150 mM NaCl (severe stress). The severe stress caused an increase in GST, GSH-Px and SODs activities from the beginning of the experiment while mild stress induced enhancement of GST activity from the second day of experiment. The maximum increase in SODs after both NaCl solutions were applied and in GST activity after the higher NaCl dose on the second day of the experiment was observed. Moreover, after 1 h of NaCl treatment with both tested NaCl solutions, the highest induction of GSH-Px activity appeared. TBARS content was elevated from the first hour of salt stress and decreased only 14 days after 50 mM NaCl application which was accompanied by high induction of GSH-Px activity. In conclusion, enhanced activities of tested enzymes indicate their involvement in early and late defence systems under salinity stress. Moreover, the dynamics of the changes in the antioxidant enzymes suggests that the second day following NaCl application is a crucial moment of the experiment with regard to salt-mediated oxidative stress.