Effect of Silver Nanoparticles and (BA) on Physiological Stress Indicators of Ocimum Basilicum L. Exposed to Lead Ions in Vitro

This study evaluated the influence of 6-benzyladenine (BA) on the initiation and multiplication of Ocimum basilicum L. under in vitro conditions and the effect of silver nanoparticles (AgNPs) on the physiological response of plantlets exposed to lead (Pb) stress. A completely randomized design (CRD) was used with appropriate replication; data were analyzed in Genstat, and means were separated using the Least Significant Difference (LSD) test at p ≤ 0.05. During initiation, BA at 1.5 mg L⁻¹ produced the highest explant response (96.67%), whereas the BA-free control showed the lowest. In multiplication, BA at 1.0 mg L⁻¹ maximized leaf number (14.0), while 1.5 mg L⁻¹ increased shoot number (3.45); plantlet height did not differ significantly. Under Pb (0, 200, 300, 400 µmol L⁻¹) and AgNPs (0, 40, 80 ppm), oxidative-stress markers and defense traits exhibited distinct main and interaction effects. Malondialdehyde (MDA; µmol g⁻¹ FW) peaked at the Pb₃×Ag₂ combination (12.22), whereas hydrogen peroxide (H₂O₂; µmol g⁻¹ FW) was highest at Pb₂×Ag₂ (4.74). Proline (µmol g⁻¹ FW) accumulated most at Pb₃×Ag₂ (80.30). For antioxidant enzymes (µmol g⁻¹ FW min⁻¹), catalase (CAT) showed its highest mean under Pb₂×Ag₁ (14.47), while superoxide dismutase (SOD) reached a maximum at Pb₃×Ag₂ (17.40). These outcomes indicate a dose-dependent, stage-specific response in basil, in which moderate AgNP levels enhance antioxidant capacity under Pb exposure, whereas higher concentrations coincide with increased oxidative load. The results support using in vitro screening to define optimal BA and AgNPs regimes that improve physiological indicators under heavy-metal stress. This clarifies the importance of AgNPs in the propagation stages and their role in tolerating stress under the influence of heavy elements, which highlights their potential practical applications in plant tissue culture and stress physiology research.