Antioxidative and proline potentials as a protective mechanism in soybean plants under salinity stress

Stress can define as all negative factors affecting plant growth. One of the most important problems among stress factors is salt stress. Antioxidant responses are tested in Soybean (Glycine max. L.) cv., "A3935" grown under 0, 50, 100 and 150 mM NaCl in order to investigate the plants protective mechanisms against salt induced oxidative stress. The NaCl treatments are repeated in four different stages of that is 10, 20 and 30 days after sowing (DAS). The plants were uprooted randomly on 30 DAS and the enzymatic antioxidant potentials were analyzed. The fresh and dry weights and the chlorophyll content are reduced with increasing NaCl concentration. Proline concentration increased at high salinity compared to untreated plants. Moreover, salinity induces a significant decline in superoxide dismutase (SOD, EC 1.15.1.1), glutathione reductase (GR, EC 1.6.4.2), ascorbate peroxidase (APX, EC 1.11.1.11) and catalase (CAT, EC 1.11.1.6) activities may be of great importance in H2O2 intoxicating mechanism under oxidative stress. As expected Na+ and Cl- concentrations in leaf and roots are higher at high salinity treatments compared to untreated plants. The concentrations of K+ are reduced with increasing NaCl concentrations.