Efficacy of copper and silver nanoparticles on seedling growth, biochemical and antioxidant potential of Capsicum annuum L., in vitro and ex vitro

Metallic nanoparticles (MNPs) were synthesized using the chemical reduction method and evaluated in vitro and ex vitro on Capsicum annuum. The impact of MNPs, namely Ag, Cu, CuAg NPs, Silver nitrate (AgNO₃), and Copper sulfate pentahydrate (CuSO₄·5H₂O) as bulk salts, on the physiological, biochemical, and antioxidative profiles of seedlings in C. annuum were examined in this work. Both NPs Primed (NPsP) and NPs Supplemented (NPsS) seeds showed 80–90 % and 90–100 % germination, respectively, after 15 days of inoculation on Murashige and Skoog medium (MS) medium, compared to the control (75 %) and 93–97 % in vitro. The seedling length, weight, and vigour index improved significantly in response to in vitro and ex-vitro NP administration. After 45 days of nanoparticle (NPs) treatment, the levels of chlorophyll and carotenoids in NPsP seedlings increased by 65–244 % and 41–203 % in ex vitro, respectively, compared to NPsS seedlings, which showed an increase of 4–114 % and 26–107 %, respectively. Additionally, the total phenolic content (TPC) and total flavonoid content (TFC) were significantly enhanced in NPsP seedlings, showing an increase of 79–173 % and 62–168 % in ex vitro, compared with NPsS seedlings, which showed an increase of 3–73 % and 22–98 %, respectively. MNPs increased the total protein content in NPsP seedlings by 26–106 % in ex vitro (5–113 %), compared to NPsS seedlings. In the NPsP seedlings, superoxide dismutase (SOD), peroxidase (POD), and proline content rose by 15–47 %, 38–83 %, and 65–121 % at ex vitro (10–61 %), (6–68 %), and proline content decreased, respectively, as compared to NPsS treated seedlings. Malondialdehyde (MDA) level in NPsP seedlings decreased (4–33 %) in ex vitro compared to NPsS seedlings, indicating ROS scavenging and healthy seedling development. In the current study, increased seed germination aided rapid seedling development. Thus, nanoparticles promote seed germination in C. annuum by overcoming the unfavourable effects of reactive oxygen species (ROS) and improving the antioxidative defence system, resulting in increased seedling development.