The beneficial effect of silicon (Si) in increasing salt stress tolerance has been observed in many plants, including the cereal crops rice, wheat, and barley. In this experiment, we examined the effect of Si on the survival and growth of torenia (Torenia fournieri L inden ex F oum) ‘ Duchess Blue and White’ cultured in vitro in the presence and absence of salt stress. Previous reports had suggested that torenia exhibited low salt tolerance. Shoot buds isolated from 16-day-old seedlings were cultured on Murashige and Skoog (MS) medium containing 0, 50, or 100 mM NaCl alone or in combination with 1.8 or 3.6 mM Si supplied as K2SiO3. Plant survival rate was significantly reduced by NaCl supplementation compared with the control. The survival rate significantly increased to 100% when 1.8 or 3.6 mM Si was added to the MS medium containing 50 mM NaCl. However, only 31% of plantlets survived when 1.8 mM Si was added to the culture medium containing 100 mM NaCl. Shoot and root lengths significantly decreased with increasing NaCl concentration in the culture medium, whereas addition of NaCl to the MS medium also significantly reduced fresh and dry weights. However, Si supplementation significantly increased fresh and dry weights under 50 mM NaCl, compared with the control. The greatest fresh and dry weights were recorded when shoot buds were cultured on MS medium containing 50 mM NaCl and 3.6 mM Si. The activities of the antioxidant-scavenging enzymes superoxide dismutase (SOD), ascorbate peroxidase (APX), and catalase (CAT), but not peroxidase (POD), were markedly higher in the presence of 50 mM NaCl than the activity of the control. When Si was added to the medium containing 50 mM NaCl, activities of SOD, POD, APX, and CAT decreased as compared with the 50 mM NaCl treatment. Thus, Si-mediated tolerance to NaCl stress was not due to increased activity of antioxidant enzymes. Although Si was not effective in increasing tolerance to high salt concentrations, such as 100 mM NaCl, the results suggested that Si supplementation could effectively enhance tolerance to 50 mM NaCl stress.

Abstract
 Introduction
 Materials and Methods
  Plant materials
  Effect of NaCl concentrations on torenia
  Effect of Si on survival and growth of shoot buds cultured under salt stress
  Effect of Si on antioxidant activity of plants cultured under salt stress enzyme extraction
  Superoxidase dismutase (SOD; E.C.1.15.1.1)
  Peroxidase (POD; E.C.1.11.1.7)
  Ascorbate peroxidase activity (APX; E.C.1.11.1.7)
  Catalase (CAT; E.C.1.11.1.6)
  Statistical data analysis
 Results and discussion
  Effect of NaCl concentrations on survival and growth of torenia
  Effect of Si on survival and growth of torenia cultured under salt stress
  Effect of Si on antioxidant activity of torenia cultured under salt stress
 References

• Eun Hye Jo(Department of Horticulture, Division of Applied Life Science (BK21 Plus Program), Graduate School of Gyeongsang National University)
• Prabhakaran Soundararajan(Genomics Division, Department of Agricultural Bioresources, National Academy of Agricultural Science, Rural Development Administration (RDA))
• Yoo Gyeong Park(Institute of Agriculture and Life Science, Gyeongsang National University)
• Byoung Ryong Jeong(Department of Horticulture, Division of Applied Life Science (BK21 Plus Program), Graduate School of Gyeongsang National University, Institute of Agriculture and Life Science, Gyeongsang National University, Research Institute of Life Science, Gyeongsang National University) Corresponding author