Benefits of Silicon Nutrition on Growth, Physiological and Phytochemical Attributes of Basil upon Salinity Stress

In the present study, improvement of salt tolerance in basil (as a salt-sensitive plant) was investigated through silicon (Si) nutrition. Basil plants were subjected to silicon (0, 3 mM) and salinity (0, 50, 100, 150 and 200 mM NaCl) for a duration of one month. Salt stress significantly decreased the biomass of basil. Si supplement (3 mM) resulted in a considerable increase (averagely +135%) in the biomass of salinized plants. Salt stress significantly decreased photosynthetic pigments concentrations, but Si supplement improved total chlorophyll concentration (averagely up to +217% compared to salinized plants). This improvement in pigment concentrations also occurred for carotenoids content (+123%). Salinity increased lipid peroxidation and H2O2 level in the aerial parts of the basil plants, but Si decreased lipid peroxidation (-49.1%) and H2O2 content (-29%) under salinity condition. Results showed salinity (alone) or together with Si, increased the level of polyphenols and also the level of radical scavenging activities in the aerial parts of basil but this effect was much more in plants co-treated with Si and salinity. Si nutrition increased the activity of SOD, APX and GPX in response to salt stress, but it did not affect CAT activity. Overall, Si supplement could induce salt tolerance in basil plants by improving photosynthesis, membrane integrity, and detoxification of toxic radicals. Furthermore, silicon increased the medicinal properties of basil via elevating its antioxidant capacity under salt stress.