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

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 the 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 primary EO constituents were 1,8-cineole (9.42-13.41%), alpha-thujone (27.40-38.73%), beta-thujone (10.11-12.94%), and camphor (11.31-16.45%). This study suggests that NPs, particularly Si and Zn, boosted plant growth by modulating Pb and Cd toxicity, which could be advantageous for cultivating this plant in areas with heavy metal-polluted soils.