Effect of potassium chloride-induced salt stress on bacoside A biosynthesis in Bacopa monnieri (L.) grown under in vitro and in vivo conditions: a comparative study

Bacopa monnieri L. is a highly acclaimed plant species for its diverse pharmaceutical properties and is mostly found in the Indian subcontinent. In this study, the effects of salt (KCl) stress on plant height, biomass, chlorophyll content, and antioxidant enzyme activities of Bacopa monnieri in both in vitro and in vivo conditions were investigated. A significant increase of up to 1.8 folds and 1.3 folds in bacoside-A content at 100 mM KCl was recorded in both in vivo and in vitro grown plants, respectively. Higher salinity (> 100 mM KCl) stress exerted a negative effect on plant height and plant biomass, whereas at levels ≤ 100 KCl, substantial improvement in terms of plant height (PH) and biomass (PB) was recorded in both in vivo (up to 1.6-fold and 1.8-fold high) and in vitro (up to 1.9-fold and 1.7-fold high) conditions. Total chlorophyll content and antioxidant enzyme (CAT, POD) activities were also maximum at 100 mM KCl. However, at higher KCl levels (200 mM), no significant increase in any of the morphophysiological parameters was recorded. Therefore, 100 mM KCl was identified as the optimum salt concentration for enhancing bacoside A content, plant growth, and physiological properties in terms of antioxidant enzyme activity and chlorophyll content in B. monnieri.