Oxidative Stress in Pea (Pisum sativum L.)-Rhizobia Symbiosis is Induced under Conditions of Salt Stress

After exposing Pea (Pisum sativum L.)-rhizobia symbiosis to two levels of NaCl (namely, 100 and 150 mM) in perlite culture, the salt-stressed plants were analyzed for nodulation, plant dry weight, total phenols, Hydrogen peroxide (H2O2), Peroxidase (PO), PolyPhenol Oxidase (PPO), and Electrolyte Leakage (EL). In results, it was observed that the shoot dry weight of all examined P. sativum-rhizobia symbiosis had a statistically significant increase. It was also ascertained that the presence of salt increased the root length as well as the root dry weight. This increase ranged between 76 and 80%, respectively, under 100 and 150 mM NaCl. The same trend was detected for the nodule number and dry weight, which increased in response to salt stress in P. sativum-rhizobia symbiosis. Under salt stress (150 mM), shoot N content was three times more than in root. A relationship was revealed between nodulation and growth that was associated with N level in shoot and root. Generally, EL values were affected by salt in leaves with variations ranging between 22 and 37% under 150 and 100 mM NaCl supply, respectively. Concerning H2O2 content in leaves, significant differences were noted in comparison to the control treatment that was stabilized after 30 days of inoculation. After 50 days of inoculation, H2O2 content in leaves was almost six times higher than after 10 days. In general, salt stress did not affect PO activity. However, PPO activity increased over time, exceeding 10 µmol g-1 FW.