Promoting effect of foliar silicon on steviol glycoside contents of Stevia rebaudiana Bertoni under salt stress

Abstract

This study investigated the effect of foliar silicon application on fresh weight and dry matter contents as well as steviol glycoside contents of stevia (Stevia rebaudiana Bertoni) grown under salt stress. In this respect, an experimental research with factorial arrangement on a Completely Randomized Design with four replications was conducted in plastic pots under greenhouse conditions. Four different salinity levels (0, 25, 50, and 75 mM NaCl) were used for three weeks old seedling and two different foliar silicone concentrations (12.5 and 25 mM) were applied in the form of sodium silicate which was launched after 4 weeks of planting. Both NaCl concentrations and foliar silicone application had statistically significant effect (p≤0.05) on fresh weight and dry matter characteristics and also on rebaudioside-A and stevioside contents of stevia leaves which were harvested before flowering period. Results showed that salt stress decreased both rebaudioside-A and stevioside contents, but foliar silicone application improve negative influences of NaCl treatments with even increasing the steviol glycoside contents. Rebaudioside-A content did not change, but stevioside content decreased with foliar silicone application in control conditions. However, highest rebaudioside-A and stevioside accumulation were recorded in 25 mM foliar silicone application under 50 mM NaCl stress. In these conditions, rebaudioside-A and stevioside contents were 112 and 26% higher than control, respectively. It could be concluded that the application of silicon significantly enhanced the plants ability to withstand salt stress conditions through increased silicon content, increased steviol glycoside production. Silicon application could therefore improve crop production under salt stress.

Keywords

• nacl stress
• rebaudioside-a
• silicon
• stevia