Variation in developmental and phytochemical characteristics of Calendula officinalis L. using foliar application of iron nanoparticles formed on hyaluronic acid

In order to study the effects of foliar application of hyaluronic acid (HA)-stabilized iron nanoparticles (0, 1, and 2 mM) on morphological characteristics as well as some other phytochemical characteristics of Calendula officinalis L., a greenhouse experiment arrangement in a randomized complete block design (RCBD) with three replications was carried out. Application of Fe nano-complex, significantly promoted all of studied parameters. The highest vegetative growth parameters were achieved by applying 1 and 2 mM Fe nanoparticles/HA (Fe NPs/ HA). Also, all photosynthetic parameters, pigments content and essential oil (EO) production significantly increased with Fe nano-complex at 1 and 2 mM concentrations. The EOs were abundant in sesquiterpene hydrocarbons, after foliar spraying. In comparison to other treated and control plants, calendula plants accumulated greater flavonoid and phenolic levels in floral parts after being exposed to 2 mM Fe NPs/HA. The calendula aqueous extracts treated with 2 mM Fe nanoparticles/HA had the lowest antioxidant activity. The results of this study showed that all pharmacological parameters had significant interactions with one another at a 2 mM rate of Fe NPs/HA.