# Responses of Medicinal and Aromatic Plants to Engineered Nanoparticles +
## 8 Conclusions  
Aromatic and medicinal plants grown in the field require low energy input for cultivation, can contribute to increasing biodiversity in agroecosystems, and their cultivation can also be used to restore degraded areas. Secondary metabolites of aromatic and medicinal plants represent a rich source of phytochemicals that can be used not only for medicinal purposes or as nutraceuticals, but also as \"lead compounds\" for the design of new drugs. Medicinal plants should generally not be grown in contaminated soil, and chemicals used in the growth or protection of crops should be kept to a minimum. On the other hand, it is desirable to ensure favorable conditions for their germination and plant growth. In this context, the use of nanoparticles, which allow a controlled release of the active ingredient and the use of a smaller amount of active ingredient to achieve the same (or even better) biological effect than in the case of bulk, has a great perspective. The use of seed nanopriming can significantly improve plant germination and growth and can be considered a suitable approach for the revegetation of medicinal plants in harsh environmental conditions. In agricultural soils with low nitrogen content, mesoporous SiO\({}_{2}\) NPs loaded with urea can contribute to achieving the desired levels of this macronutrient. On the other hand, in calcareous soils characterized by a lack of micronutrients (especially Zn and Fe), mineral fertilization of medicinal and aromatic plants using nanoscale particles of these essential nutrients or their oxides can be favorable. In particular, foliar spraying with nanosizedmetal fertilizers allows maximum use of plant nutrients and contributes to the fortification of plants with essential micronutrients. In general, low-concentration nanoparticles applied in such treatment do not contribute to environmental contamination and do not pose a risk to non-target organisms. Medicinal plants, especially their essential oils containing secondary metabolites, show many biological activities, e.g., anti-inflammatory, antimicrobial, antiviral, antidiabetic, anticancer, etc. Oxidative stress induced by NPs stimulates the production of these valuable compounds, not only in medicinal and aromatic plants grown in the field, but also with higher efficiency in tissue and hair root cultures of these plants. Therefore, these \"green\" in vitro methods, which do not use harmful solvents, can be promising for the efficient production of these beneficial bioactive metabolites. Utilizing the ability of nanoparticles to mitigate the adverse impact of abiotic stresses on medicinal and aromatic plants can be particularly useful in changing climatic conditions, where longer periods of drought and elevated temperatures can be expected in the near future. Increased plant tolerance to salts due to the application of nanoparticles will facilitate the cultivation of medicinal and aromatic plants in soil with higher salinity without adversely affecting their performance. Medicinal and aromatic plants have been associated with the human population since ancient times; their popularity as alternatives to synthetic drugs is currently growing, and the use of appropriate nanoparticles can significantly contribute to their better yield, production of higher concentrations of valuable metabolites, and better nutritional value.  
[PERSON] and [PERSON] composition and writing. Both authors have read and agreed to the published version of the manuscript.  
This study was supported by the Slovak Research and Development Agency (projects APVV-17-0373 and APVV-17-0318), and by the Slovak Grant Agency for Science (VEGA 1/0787/18).  
Not applicable.  
The authors declare no conflict of interest.