Comparative study the effect of the external treatments of silicon and ascorbic acid on antioxidant capacity of Basil (Ocimum basilicum L.) under salt stress

Basil (Ocimum basilicum L.) belongs to Lamiaceae and is relatively sensitive to salinity. Salinity is one of the most important factors limiting crop production. This study was conducted in a three-replicate completely randomized factorial design to comparative investigate the effects of different concentration of silicon (SiO4-2) application [control (without Si), 1 and 2 mM] and ascorbic acid [control (0), 25 and 50 mM] on membrane stability index (MSI), lipid peroxidation and hydrogen peroxide production (H2O2) and the antoxidant capacity (peroxidase, polyphenol oxidase, catalase and ascorbate peroxidase activities, proline and soluble sugars content) of Basil under three levels of salinity (0, 100 and 200 mM). Although proline and soluble carbohydrates content of Basil were increased by external silicon treatment under salinity, application of ascorbic acid could play an important role in reducing the lipid peroxidation and H2O2 content in the situation of salinity stress. The results showed that the activities of all examined enzymes increased at high level of salinity, but the use of silicon and ascorbic acid lead to a further and significant increases of enzyme activities in leaves. Based on the results of this survey, ascorbic acid and silicon consumption as external treatments could boost the immune system of Basil and would be good candidates to reduce the detrimental effects of salinity on the survival and growth of the plant.