Nitrogen affects growth, steviol glycosides, leaf gas exchanges and chlorophyll fluorescence in Stevia rebaudiana Bert.

This study focused on the agronomic, physiological and biochemical response of Stevia rebaudiana Bertoni grown under different nitrogen (N) rates. Consequently, a pot trial experiment in open air conditions was set up with the aim to define the effects of four different N rates on leaf gas exchanges, chlorophyll fluorescence, Rubisco activity, photosynthetic pigments and photosynthetic N use efficiency (PNUE) as well as on productive characteristics and steviol glycoside content. The results demonstrate that using an appropriate N rate it is possible to improve rebaudioside A content, rebaudioside A/stevioside ratio, photosynthetic CO2 assimilation, stomatal conductance, PNUE, Rubisco activity and PSII efficiency. Our study highlights that through N it is possible to modulate the SG biosynthesis, with a significant increase in the rebaudioside A content and in the ratio between rebaudioside A and stevioside.