The role of antioxidant responses on the tolerance range of extreme halophyte Salsola crassa grown under toxic salt concentrations

• Salinity increased reactive oxygen species (ROS) in S. crassa.
• Salt stress decreased RGR, RWC and ΨΠ.
• S. crassa exhibited inductions in TBARS in response to extreme salt concentrations.
• Salinity caused an increase in CAT, POX, GR and GPX at 15 d.
• S. crassa is tolerant to salt-induced damage at short salt treatments.

Salsola crassa (Amaranthaceae) is an annual halophytic species and naturally grows in arid soils that are toxic to most plants. In order to study the effects of salinity on their antioxidant system and to determine the tolerance range against salt stress, S. crassa seeds were grown with different concentrations of NaCl (0, 250, 500, 750, 1000, 1250 and 1500 mM) for short (15 d) and long-term (30 d). Results showed that growth (RGR), water content (RWC) and osmotic potential (ΨΠ) decreased and, proline content (Pro) increased at prolonged salt treatment. Unlike K+ and Ca2+ contents, S. crassa highly accumulated Na+ and Cl− contents. Chlorophyll fluorescence (Fv/Fm) only decreased in response to 1500 mM NaCl at 30 d. No salt stimulation of superoxide anion radical (O2
• −) content was observed in plants treated with the range of 0–500 mM NaCl during the experimental period. NaCl increased superoxide dismutase (SOD) activity depending on intensities of Mn-SOD and Fe-SOD isozymes except in 1500 mM NaCl-treated plants at 30 d. In contrast to catalase (CAT), peroxidase (POX) activity increased throughout the experiment. Also, salinity caused an increase in glutathione reductase (GR) and glutathione peroxidase (GPX) and decreased in ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR) and dehydroascorbate reductase (DHAR) at 15 d. Both total ascorbate (tAsA) and glutathione (tGlut) contents significantly increased in treated plants with 1000–1500 mM NaCl at 15 d. After 0–1000 mM NaCl stress, H2O2 and TBARS contents were similar to control groups at 15 d, which were consistent with the increased antioxidant activity (POX, GR and GPX). However, H2O2 content was more pronounced at 30 d. Therefore, S. crassa exhibited inductions in lipid peroxidation (TBARS content) in response to extreme salt concentrations. These results suggest that S. crassa is tolerant to salt-induced damage at short-term treatments as well as extreme salt concentrations.