Investigation of Spermine pretreatment on some growth and physiological parameters of medicinal pumpkin (Cucurbita pepo L.) under salinity stress

Spermine (Spm) is a group of polyamine compounds that has four groups of nitrogen (tetraamine) and therefore has a higher buffering capacity that is capable of enhancing plant defense systems against many environmental stresses. In this study, which was conducted in 2016 in the research greenhouse of the Graduate University of Advanced Technology, the protective effects of Spm pretreatment against the toxicity of salinity were investigated in pumpkin. For this purpose, Spm was added at 0.1 and 1 mM to the hydroponic medium for 5 days before stress. Salinity treatment (NaCl) was applied at three levels of 0, 40 and 80 mM for 7 days. The experiments were conducted in factorial form in a completely randomized design with three replications. The results showed that salinity stress significantly decreased growth parameters (fresh and dry weight of shoot and root), leaf water content (RWC), protein content and increased lipid peroxidation and ion leakage. In addition, the amount of proline, gamma-aminobutyric acid (GABA) and the activity of antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), guaiacol peroxidase (GPOX) and ascorbate peroxidase (APX) increased under salt stress. Pretreatment with Spm improved growth and increased plant resistance against salt stress. Spm by increasing antioxidant activity (SOD, CAT, GPOX, and APX), proline and GABA content reduces oxidative stress, lipid peroxidation, ion leakage and finally, increased growth parameters. Therefore, Spm pretreatment is suggested as an efficient strategy to improve plant growth and raise pumpkin tolerance against salt stress.