Impact of foliar applications of MeJA and MgO-NPs on secondary metabolites and essential oil of Rosa damascena Mill

In recent years, use of elicitors in agriculture has received attention due to their positive effect on plant secondary metabolite production. We investigated the effects of two elicitors, magnesium oxide nanoparticles (MgO-NPs) and methyl jasmonate (MeJA) on secondary metabolites that improve physiological and stress-defensive properties of leaves and flowers of Rosa damascena Mill. Different doses of the elicitors were tested, and their impacts assessed for 14 days after the leaf treatment, and at three stages of flowering. Significant increases in the contents of reactive oxygen species (ROS) and reactive nitrogen species (RNS), and in the activities of enzymatic and non-enzymatic antioxidants were found in leaves treated with the two elicitors. However, the effect was higher and widespread on all investigated parameters in plants treated with the lowest dose (0.1 mM) of MeJA. Low concentrations of MeJA also clearly stimulated synthesis of monoterpenoid alcohols and aromatic alcohols that are responsible for the perfume of petals, and enhanced total and single phenolics, and total flavonoids of flowers. In contrast, petal anthocyanins were reduced following treatments with both elicitors. Exogenous applications of low concentrations of MeJA appear to be the most promising for inducing antioxidant responses in R. damascena and improving perfumes of the petals.