Effect of salt stress on the morphology, physiology and biochemical parameters of Withania somnifera (L.) Dunal: A medicinally important plant

Salt stress negatively impacts the growth of medicinal plants like Withania somnifera (L.) Dunal, resulting in loss of biomass and usability of its therapeutic secondary metabolic compounds, such as withanolides. This study investigates the effects of varying salinity levels (0 mM [control], 25 mM, 50 mM, 75 mM, 100 mM, 125 mM, 150 mM, 175 mM and 200 mM) on the morphological, growth and physiological parameters of W. somnifera. Morphological traits such as shoot length, root length and fresh and dry weight of the plants showed a negative correlation with salt stress. The results of biochemical analysis indicate a noticeable decline in chlorophyll a, b and total chlorophyll content, carbohydrate and protein levels with increasing salt concentration, while important phytochemicals like proline, phenols and flavonoid content exhibited an increase, consequently increasing the antioxidant activity executed by such metabolites as well. Most notably, Withaferin A and Withanolide A, important secondary metabolites responsible for the therapeutic properties of the plant, showed conflicting trends, with Withanolide A decreasing but Withaferin A increasing with an increase in stress, suggesting differences in the activities of their metabolic pathways under stress. The findings highlight the significant impact of salinity on both the growth and medicinal quality of W. somnifera, with the increase in Withaferin A with stress indicating an opportunity to explore this trend for achieving higher yield for commercial use in the pharmaceutical industry.