Innovative and sustainable catechin-based nanocomposites for enhancing salinity tolerance and secondary metabolite production in Stevia rebaudiana (Bertoni) Bertoni

Integrating innovative and sustainable nano-enabled technologies in agriculture has opened new avenues for enhancing crop resilience against abiotic stressors. Salinity stress is a major abiotic challenge that adversely affects medicinal plants' growth, productivity, and secondary metabolite synthesis, like Stevia rebaudiana (Bertoni) Bertoni. This study introduces a novel catechin-based nanocomposite synthesized using a bio-derived approach to improve stevia’s resistance to salinity stress. Catechin, a potent antioxidant derived from natural sources, was chosen for its well-documented ability to neutralize oxidative stress and enhance plant defence mechanisms under abiotic stresses. Salinity stress significantly hampers stevia’s growth and secondary metabolite production, which is crucial for its industrial exploitation. Catechin-based nanocomposites were synthesized using carboxymethyl cellulose as a biocompatible carrier, ensuring stability and effectiveness. The nanocomposites were characterized and tested at several concentrations (0, 0.01, and 0.1 mg/mL) on stevia plants under varying levels of NaCl (0, 50, and 100 mM). Salinity stress reduced plant growth, photosynthetic pigments, and the K/Na ratio while increasing oxidative stress markers like hydrogen peroxide and malondialdehyde. However, catechin-based nanocomposites improved these physiological and biochemical parameters, enhancing photosynthetic efficiency, antioxidant enzyme activity, and ion balance. Catechin nanocomposites showed protective effects on nitrogen and polyamine metabolisms, involved in stress defensive responses, while increasing levels of the valuable secondary metabolites stevioside and rebaudioside A. The research demonstrates the potential of utilizing bio-based catechin nanocomposites as a green solution in reducing salinity stress, thus showing a potentially viable means of improving resilience and commercial yields in stevia and other plants growing under stress conditions.