Impact of Titanium Dioxide Nanoparticles on the Evaluation of Mint Oil (Mentha Spicata L.) Using some Physiological Analyses and Molecular Markers

To evaluate the impact of Titanium dioxide nanoparticles on pigments, minerals, and essential oil of Mentha spicata L. five treatments of biologically and chemically synthesized TiO₂NPs were applied to spearmint leaves. Results showed that 50 mg/L BNT-treated plants had the highest contents of chlorophyll (a) and total chlorophyll, while 25 mg/l CNT-treated plants recorded the highest carotenoids and micronutrients (Fe, Mn, Cu, Na, and Zn) contents. Spearmint oil constituents were determined by Gas Chromatography-Mass spectroscopy (GC-MS), which demonstrated the positive effect of TiO₂NPs on improving the spearmint oil constituents, as some therapeutic compounds appeared in CNT, BNT, CNTN, and PC compared to the negative control. Also, the percentage of some compounds increased in all treatments, while the percentage of the toxic compound isopulegone decreased or disappeared at all.
               Random Amplified Polymorphic DNA (RAPD) markers were also used for the assessment of genetic variation between different treatments of Titanium dioxide nanoparticles on Mentha spicata L. in comparison with the control. A total of 10 arbitrary sequence primers were evaluated. All 10 primers used for the RAPD analysis showed consistent band patterns. In total, scorable bands were observed with the primers. The total number of amplicons produced per primer varied from 7 for OPA-09 and OPB-10 to as many as 13 bands for OPA-4. The average number of bands per primer was 9.9. Out of 99 bands, 31 were polymorphic (31.31%). The average number of polymorphic RAPD bands was 3.1 per primer. The highest similarity (94%) with the negative control was recorded in spearmint leaf treated with Titanium dioxide nanoparticles that were chemical source-derived amended with nitrogen, while spearmint leaf treated with Titanium dioxide nanoparticles that biological source-derived amended with nitrogen was found to show the least similarity (88%) with the negative control. In this concern, RAPD results have been suggested to be useful fast methods for comparing genetic changes and variation in plants.
             Overall, the results of the present investigation indicated that the foliar application of TiO₂NPs (CNT, BNT, and CNTN) on Mentha spicata L. has a significant positive effect on micronutrients and pigment contents, besides improving the spearmint oil quality. The differences within treatments were also affirmed by the genetic markers of the RAPD technique.