Foliar application of silicon, selenium, and zinc nanoparticles modulate lead and cadmium toxicity in sage (Salvia officinalis L.) plants by optimizing growth and biochemical status and minimizing metal accumulations

Different techniques have been used to alleviate metal toxicity in medicinal plants, accordingly, nanoparticles (NPs) have a noticeable interest in modulating oxidative stresses. Therefore, this work aimed to compare the impacts of silicon (Si), selenium (Se), and zinc (Zn) NPs on growth, physiological status, and essential oil (EO) of sage ( Salvia officinalis L.) treated with foliar application of Si, Se, and Zn NPs upon lead (Pb) and cadmium (Cd) stresses. The results showed that Se, Si, and Zn NPs decreased Pb accumulation by 35, 43, and 40%, and Cd concentration by 29, 39, and 36% in sage leaves. Shoot plant weight showed a noticeable reduction upon Cd (41%) and Pb (35%) stress; however, NPs, particularly Si and Zn improved plant weight under metal toxicity. Metal toxicity diminished relative water content (RWC) and chlorophyll, whereas NPs significantly enhanced these variables. The noticeable raises in malondialdehyde (MDA) and electrolyte leakage (EL) were observed in plants exposed to metal toxicity, however, they were alleviated with foliar application of NPs. The EO content and EO yield of sage plants decreased by the heavy metals but increased by the NPs. Accordingly, Se, Si, and Zn NPS elevated EO yield by 36, 37, and 43%, respectively, compared with non-NPs. The GC/MS analysis showed that the primary EO constituents were 1,8 Cinoele, α-thujone, β-thujone, and camphor with different amounts of heavy metals and NPs. According to principal component analysis (PCA), α-thujone and camphor were justified by F1, while 1,8 cineole and β-thujone were explained by F2. This study showed that NPs especially Si and Zn increased plant growth by modulating Pb and Cd toxicity.