Salt Stress Elevates Endogenous Phytohormones and Activates Antioxidative Defense System in Leaves of Spinacia oleracea (Spinach)

Abstract

Aims: Salinity stress is one of the major environmental stresses and continues to limit the growth and productivity of most food crops. Therefore, the aim of this research was to evaluate the effects of salinity stress on endogenous phytohormones and antioxidative defense system of Spinacia oleracea. Study Design: Salinity stress was induced using three concentrations (50 mM, 100 mM and 150mM) of sodium chloride (NaCl). The treatments were laid out in complete randomized blocks with three replicates each. Place and Duration of Study: The experiment was conducted in the screen house of the Department of Biochemistry, University of Ibadan, Nigeria for eight weeks. Methodology: After eight weeks of planting on saline soil, fresh leaves were harvested and biochemical analysis was carried out on the leaves to determine the effect of salinity stress on photosynthetic pigments, minerals, antioxidative enzymes, indole-acetic acid (IAA) and gibberellic acid (GA) using standard methods. Data were statistically analyzed by one way ANOVA and Duncan's multiple range tests were performed to test the differences among treatments at P<0.05. Results: Results showed that treatment with 150 mM NaCl increased the level of IAA, GA,  catalase (CAT), superoxide dismutase (SOD)  and sodium significantly (P<0.05) in Spinacia oleracea leaves, while photosynthetic pigments, glutathione peroxidase, magnesium, manganese, potassium and iron were significantly decreased (P<0.05). Conclusion: These results suggest that Spinacia oleracea responds to salinity stress via an elevation of CAT, SOD, IAA and GA.