Efficacy of titanium dioxide nanoparticles in modulating photosynthesis, peltate glandular trichomes and essential oil production and quality in Mentha piperita L.

Nanoparticles have an edge over normal elemental forms because of the novel physicochemical properties they possess, which enable them to act as plant growth promoters. The purpose of the present inquest was to investigate the effect of the Titanium dioxide nanoparticles (TiO2 NPs) on the enzymatic activities, photosynthesis, nutrient acquisition and essential oil (EO) production in peppermint. Effect on the peltate glandular trichome density and diameter was also studied. Out of the different concentrations of TiO2 NPs (0, 50, 100, 150, 200 and 250 mg L−1) tested on the plant, 150 mg L−1 proved optimum for most of the parameters, if however, 100 and 150 mg L−1 were equally significant in some cases. A maximum increase of 17.7% and 19.1% was reported in the nitrate reductase and carbonic anhydrase activities respectively by 150 mg L−1 at 150 days after planting (DAP) compared to untreated plant. Chlorophyll fluorescence and net photosynthetic rate exhibited a maximum enrichment of 7.2% and 23.8% respectively by 150 mg L−1 over control. Furthermore, EO content and yield of the plant were also significantly enhanced by 39.4% and 105.1% respectively over control. The quality of the EO also improved as an increase of 9.6% and 124.1% was observed in the content and yield of menthol over control in the present study. Keywords: Essential oil, Stomatal conductance, Chlorophyll fluorescence, Menthol, Trichomes, Mentha piperita L