Foliar co-application of zinc oxide and copper oxide nanoparticles promotes phytochemicals and essential oil production in dragonhead (Dracocephalum moldavica).

Individual nanoparticle application has been documented to promote plant production; however, whether co-application of two nanoparticles (NPs) is more sustainable and significantly promotes plant production is unclear. Herein, foliar co-applications of two NPs or their conventional fertilizer forms on the growth, micronutrient (copper and zinc) enrichment, primary productivity, and essential oil (EO) production in a medicinal annual, dragonhead (Dracocephalum moldavica L.), were investigated.

Foliar enrichment of copper oxide nanoparticles promotes biomass, photosynthetic pigments, and commercially valuable secondary metabolites and essential oils in dragonhead (Dracocephalum moldavica L.) under semi-arid conditions.

High alkaline and low organic carbon hinder micronutrients, such as copper (Cu), bioavailability in (semi-) arid soils, affecting plant nutrient quality and productivity. This study aimed at investigating the potential beneficial effects of foliar Cu oxide nanoparticles (CuONPs) and conventional chelated-Cu applications (0-400 mg Cu/L) on the biomass, physiological biomarkers of plant productivity and oxidative stress, Cu bioaugmentation, and essential oils and secondary metabolites in dragonhead (Dracocephalum moldavica [L.]) grown in Cu-limited alkaline soil in semi-arid condition.