# Responses of Medicinal and Aromatic Plants to Engineered Nanoparticles +
## 4 Effect of Metal-Based NPs on Medicinal and Aromatic Plants
### Copper-Based NPs  
#### 4.2.1 Impact on Plant Growth and Photosynthesis  
_Capsicum annuum_ plants grown in soil amended with 500 mg/kg CuNPs, which were evaluated at the vegetative stage, i.e., 45 days post transplantation, showed pronouncedly increased length and dry weight of roots, while plant tissues accumulated lower Cu amounts compared to treatment with bulk Cu particles. On the other hand, when treated plants were evaluated in the reproductive stage, i.e., 90 days post transplantation corresponding to a full life cycle, treatment with 500 mg/kg CuNPs resulted in increased photosynthesis, stomatal conductance, and Cu leaf content compared to that observed with application of bulk Cu particles. Treatment with 62.5 mg/kg CuNPs was found to increase transpiration, but total sugar, carotenoid, Chl, and vitamin C contents in the fruit, and the root and leaf enzyme activity, were not affected 90 days post transplantation in plants exposed to 62.5, 125, or 500 mg/kg CuNPs. The results of this experiment suggested that a dose of 500 mg /kg CuNPs, ensuring higher Cu bioaccumulation in the root, and leaf tissue over long-term exposure, is suitable to be used as a nanofertilizer (201). CuO NPs phytosynthesized using _Punica grantnum_ peel extract foliarly sprayed on _Capsicum annuum_ plants increased the height of plants, as well as growth and the Chl content of leaves; the fruit practically did not contain residues of sprayed NPs (202). Application of 125 mg/kg CuO NPs to _Capsicum annuum_ plants significantly reduced leaf P content by 41%, while exposure to 500 mg/kg CuO NPs decreased Zn content in leaves and fruits by 55% and 47%, respectively, compared to the control, thereby affecting the nutritional quality of bell pepper (203).  
Foliar spraying of _Mentha piperita_ L plants performed three times of the interval of 15 days up to flowering stages with 1.0 g/L CuNPs was found to enhance Chl content and EO percentage of 35% and 20%, respectively, as compared to control (133). Investigation of the clonal microreproduction of _Mentha longifolia_ plant showed that addition of colloidal solutions of CuNPs (0.5 mg/L) and CoNPs (0.8 mg/L) to MS nutrient medium resulted in an increase of microplant height and growth index on 45-48.4%, the quantity of internodes on 29.4-33.9%, quantity of shoots on 55.6-66.2%, and reproduction coefficient on 30-40% (204). Application of 5 uM CuNPs (20-40 nm) for plant regeneration of _Ocimum basilicum_ via somatic embryogenesis resulted in 5.6-fold higher percentage of explants produced somatic embryos (84 vs. 15%) and 4.35-fold higher average number of regenerated plantlets/explant (18.7 vs. 4.3) as compared to treatment with 0.1 uM CuSO\({}_{4}\) 5 H\({}_{2}\)O (205). Exposure of _Origanum vulgar_ plants for 60 days to CuNPs at doses 0-200 mg Cu/kg increased root and shoot growth, and water content, but reduced shoot biomass, as well as starch, total sugar, and reducing sugar in leaves; whereas shoot length, MDA, and Chl levels were not affected. However, CuNPs affected root and shoot contents of Ca, Fe, Mg, and Mn, suggesting that nutrition value of oregano could be modified (206). Phytotoxic effect of 200, 400, and 800 mg/L CuNPs on hydroponically cultivated coriander (_Coriandrum sativum_) plants was reflected in reduced biomass and root length, lower levels of ChIs (ChIs and Chl) compared to control plants, and increased levels of H\({}_{2}\)O\({}_{2}\) compared to untreated plants (207).