Plant elicitation and TiO2 nanoparticles application as an effective strategy for improving the growth, biochemical properties, and essential oil of peppermint.

Abstract

MenthapiperitaL., which is an abundant source of essential oils (EO) and phenolic acids, is well known for its medicinal significance. The present research aimed to evaluate the impact of various concentrations of methyl jasmonate (MeJA; 0, 0.1, and 0.5mM), titanium dioxide nanoparticles (TiO2 NPs; 0 and 150mg L-1), and salicylic acid (SA; 0, 0.1, and 1mM) on growth, EOs, and phenolic compounds ofM.piperitaL. The results demonstrated that the simultaneous application of SA (0.1mM) and TiO2 NPs (150mg L-1) enhanced shoot dry weight, the shoot length, and membrane stability index of peppermint by 56.17, 19.52, and 36%, respectively, compared to control. Moreover, phenolic content (76%), caffeic acid content (78%), rosmarinic acid content (87%), 2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging ability (78%), and catalase (155%), ascorbate peroxidase activities (95%) were further improved by simultaneously applying MeJA (0.1mM) and TiO2 NPs (150mg L-1) compared to control. The highest menthol production (44.51%) was obtained with exogenous application of MeJA (0.1mM) with 150mg L-1 TiO2 NPs. The findings of the current study presented an ideal combination of TiO2 NPs with plant growth regulators for promoting antioxidant activities and increasing major components of EO in peppermint plants.