—Supplying the nutritional demands of plants using coated nanoparticles (CNPs) is a novel methodology to increase nutrient’s efficiency and simultaneously reduce the adverse effects of salinity. This study evaluated the effect of iron nanoparticles foliar application on the growth and physio-biochemical parameters of spearmint (Mentha spicata L.) under salinity stress. Uncoated iron nanoparticles (15 and 30 μm L–1) and coated ones with chitosan and citral (15 and 30 μm L–1) were foliar sprayed under salinity stress (0, 30, and 60 mM NaCl) on the plants. FE-SEM and EDX analyses confirmed the morphological and chemical structure of the iron nanoparticles coated with high molecular weight citral and chitosan. The results showed a significant increase in carotenoid content at 60 mM salinity. In all iron nano-oxide forms; there was a significant increase in proline and sugar content, fresh and dry weight of roots and shoots, chlorophyll and anthocyanin content, relative water content, and essential oil content of the plants. The moderate concentrations of iron nanoparticles with citral coating under salinity conditions enhanced the leaf number, plant height, root, shoot, and plant fresh and dry weight, chlorophyll a content, root and shoot proline content, and, root sugar content of spearmint plants. Overall, salinity adversely impacted the growth parameters, but foliar treatments with citral-coated nano-Fe ameliorated the salinity depression in plants. The results of more detailed studies would be advisable for the extension section
