Impact of nutrient supply on growth and synthesis of metabolites of in vitro shoot cultures of S. rebaudiana

Stevia rebaudiana plants produce sweet tasting compounds, steviosides, which are 300 times sweeter as sugar and can be used as natural sweeteners. Moreover, stevia leaves contain high amount of antioxidants. The use of plant compounds as components of functional nutrition and nutraceuticals is extremely relevant today. The purpose of this study was to investigate the effect of increased nitrogen and saccharose supply on growth and accumulation of steviosides and anthocyanins as well as antioxidative activity in fast-growing shoot cultures of S. rebaudiana. The morphological changes of the leaves, the accumulation of steviosides and anthocyanins, and the antioxidant properties of the extracts were determined. It was shown that during three weeks of in vitro cultivation of shoots on MS medium with double concentration of nitrogen, the biomass increased by 71.0%, after application of double concentration of saccharose – by 133%, and after increasing nitrogen in combination with saccharose supply – by 162.0% compared to the control. Sucrose stimulated the accumulation of biomass. Anti-oxidative potential after nitrogen application was 2.4 times higher than the control, and with saccharose supply it increased 2.7 times. Shoots treated with increased nitrogen and saccharose concentration contained 50.7 and 57.8 mg/g-1 steviosides, respectively. However, the combination of nitrogen and saccharose led to accumulation of 73.4 1 mg/g-1 steviosides. Shoots grown on MS medium culture had 26.0 mg/g-1 of steviosides. The content of anthocyanins was 1.7 times greater under added nitrogen supply, and 2.3 times greater after the application of nitrogen and saccharose. Optimum cultivation media developed individually for each in vitro culture increase the production of valuable plant secondary metabolites up to 3 times