Antioxidant enzymes and non-enzymatic antioxidants as defense mechanism of salinity stress in cowpea (Vigna unguiculata L. Walp)—Ife brown and Ife bpc

Abstract

Abstract Background Several mechanisms had been exhibited by plants to mitigate deleterious effects of salinity stress. A screen house experiment was conducted to investigate the effects of salinity stress on the activities of osmolytes (antioxidative and non-antioxidative enzymes) in the leaves of two cowpea (Vigna unguiculata L. Walp)—Ife brown and Ife bpc, with the aim of better understanding the biochemical mechanisms of salt tolerance. Salts of sodium chloride (NaCl) and sodium sulfate (Na2SO4) at 5, 10 and 15 dS/m concentrations were used for this study. The saline solution was prepared following standard methods. Proline, lipid peroxidase (LP), superoxide dismutase (SOD) and glutathione (GSH) were determined following standard protocols. Results Results showed that minimum proline content (12.07 mg/g) and maximum proline determination (16.05 mg/g) were observed in Ife bpc at 5 and at 15 dS/m under NaCl and Na2SO4 treatments. The LP content significantly increased in Ife brown at 15 dS/m under NaCl treatment and at 10 dS/m (9.49 mg/g) under Na2SO4 salinity. Minimum GSH content (120 µm/g) and maximum glutathione accumulation (138.97 µm/g) were observed in Ife bpc in the stressed cowpea seedlings (5 and 10 dS/m) under NaCl treatment with respect to the control. Also, SOD activities in the leaves of Ife brown increase with increase in salinity stress in both NaCl and Na2SO4 treatments. Conclusions This study concludes that the accumulation of enzymatic and non-enzymatic antioxidants is capable of detoxifying and scavenging reactive oxygen species, thereby mitigating salinity-induced oxidative damage.