Biostimulant Effect of Sargassum Vulgare Extract on morpho-physiological and Biochemical Traits of Salt-stressed Tomato Plants (Solanum Lycopersicum L)

Purpose This study aimed to assess the effect of Sargassum vulgare extracts (SVE) on tomato plants (Solanum lycopersicum L.) exposed to salinity stress. Methods We evaluated the impact of SVE concentrations (2%, 5%, and 10%) prepared by the water extraction method using fresh material on the morphophysiological and biochemical parameters of tomato seedlings subjected to salinity (50 mM NaCl). Results Our results showed that salinity reduced tomato plant growth compared to the control. However, supplementing stressed plants with lower SVE concentrations, particularly 2%, increased plant height, biomass, and chlorophyll content by 32.24%, 38%, and 55%, respectively, compared to stressed plants without SVE application (positive control). Moreover, 2% of SVE decreased hydrogen peroxide and malondialdehyde levels by 17.24% and 31.54%, respectively. There was also an increase of 23.89%, 133.34%, and 16.36% in the activity of the antioxidant enzymes: glutathione S-transferase (GST), glutathione peroxidase (GPx), and superoxide dismutase (SOD) with treatments of 2%, 5%, and 10% of SVE, respectively, compared to the positive control. Additionally, SVE treatment enhanced indole acetic acid, polyphenols, flavonoids, soluble sugars, and amino acid content. Furthermore, 2% of SVE increased the activities of enzymes involved in carbon and nitrogen metabolism: phosphoenolpyruvate carboxylase (PEPC), malate dehydrogenase (NAD-MDH), and aspartate aminotransferase (AAT) by 42.47%, 186.23%, and 4.6%, respectively; and glutamine synthase (GS) and glutamate dehydrogenase (GDH) by 185.71% and 0.75%, respectively, in the case of treatment with 10% SVE. Conclusion Our research suggests that SVE holds the potential to serve as biostimulant, improving tomato plants' salt stress tolerance.