Physiological and morphological features denote that salt stress in Stevia rebaudiana is based on nonstomatic instead of stomatic limitation

Abstract

Stevia rebaudiana is a very widespread plant throughout the world, due to the production of diterpenic steviol glycosides, with high sweetening power, being up to 300 times sweeter than sugar at a concentration of 0.4% (w/v). In the Colombian Caribbean, research has focused on evaluating the adaptation and management of commercial genotypes and experimental lines, however, their behavior against soil salinization is unknown. The objective of this research was to evaluate the response of some physiological and morphological characteristics of two promising genotypes against salt stress. The relationship between gas exchange, chlorophyll a fluorescence, and growth parameters was modulated as a function of the NaCl concentration. Although stomatal conductance and perspiration did not show a response to salt levels, the reduction in net photosynthesis as salinity increased was not associated with stomatal effects, but rather with a drop in the rate of electron transport, which articulates the absorption of light energy and its conversion into photoassimilates. Therefore, it could be inferred that salinity-stressed S. rebaudiana plants are more sensitive to non-stomatal limitation than to stomatal limitation.