Silver nanoparticles mitigated cadmium toxicity in tobacco by modulating biochemical, cellular and genetic responses

Abstract

Cadmium (Cd) contamination in soil has a hazardous impact on tobacco growth. The present study investigated the role of soil-applied silver nanoparticles (Ag-NPs) in reducing Cd stress in tobacco by exploring morphological traits, photosynthetic efficiency, ROS (H₂O₂ and O₂·⁻) levels, antioxidants as defense markers, cell death/viability, cellular and subcellular structural changes, and real-time qRT-PCR-based gene expression analysis. The treatments comprised a control (CK), 20 mg kg⁻¹ cadmium (Cd) stress, 50 μM amino silver nanoparticle (Ag-NP) suspension, and combined cadmium and silver nanoparticle (Cd + Ag-NP) application. Results indicate that tobacco leaves recorded the maximum Cd content (144.53 μg g⁻¹), followed by stems (70.96 μg g⁻¹) and roots (50.15 μg g⁻¹). SEM and TEM analyses indicated Cd-induced stomatal injury and massive damage at the subcellular level. Confocal microscopic visualization clarified ROS accumulation and cell death caused by Cd-mediated redox imbalance. However, the application of Ag-NPs effectively reduced Cd bioaccumulation (BCF) and the root-to-shoot Cd translocation (TF) rate. Moreover, the Ag-NP application (Cd + Ag-NPs) mitigated Cd-induced oxidative damage by improving the activities/levels of the antioxidants APX, AsA, and SOD by 248.45%, 132.67% and 29.43%, respectively, compared with Cd alone. Ag-NPs also upregulated the expression of genes related to growth, chlorophyll, carotenoid biosynthesis, and antioxidative defense. Therefore, Ag-NPs can be employed as a sustainable approach to reduce the environmental toxicity impact of Cd and ensure food safety.