The effect of foliar application of zinc oxide and zinc nanoparticles on growth, photosynthetic pigments and essential oil compounds of green basil

Zinc as an essential micronutrient element has an important impact on the growth and metabolism in plants. This experiment was carried out to evaluate the effect of foliar application of zinc on growth, photosynthesis pigments, and essential oil quantity and quality of basil under greenhouse conditions. The treatments were four levels zinc oxide (0, 25, 50, 100 mg/L) and four levels zinc oxide nanoparticles (0, 25, 50, 100 mg/L). The results showed that foliar application of zinc had significant influence on the evaluated parameters. Treatments of Zinc oxide and zinc nanoparticle significantly increased plant length, plant wet and dry weights, leaf number per plant, photosynthesis pigments contents and essential oil percent, and in this regard, zinc nanoparticle impact was more effective than zinc oxide. The highest growth parameters and pigments content were observed at 100 mg/l zinc nanoparticle. Based on the results, 34 components were identified in the basil essential oil that maximum amounts were oxygenated monoterpenes, and three main components were methyl chavicol, linalool and alpha-cadinol. Also, maximum amount of methyl chavicol and alpha-cadinol was observed under 50 mg/l nanoparticles. Zinc has probably increased growth and production of essential oils in basil by increasing the growth hormones, improving the uptake of some nutrients, and increasing the synthesis of precursors of secondary metabolites. The findings of this study showed that the effect of zinc nanoparticle was more effective than zinc oxide in increasing growth and active substances of basil.