## 2 Phytotoxic Effects of Volatile Terpenes from the Lamiaceae Family
### Advantages of Water Emulsions of Nepeta Essential Oils
[39] conducted a valuable study that provides deeper insights into the complex interactions between synthetic herbicides and natural bioactive compounds. Contrary to expectations, foliar application of a water emulsion of _Nr_EO rich in _trans,cis_-NL, together with the synthetic herbicide phosphinothricin (PPT)--BASTA(r) (manufactured by BASF SE, Ludwigshafen, Germany; formerly by Bayer Crop Science AG, Germany), was shown to mitigate phosphinothricin-induced ammonium toxicity in the model plant _Arabidopsis thaliana_ ([PERSON], grown in a greenhouse, indicating an antagonistic effect. Phosphinothricin inhibits glutamine synthetase (GS), one of the most important enzymes in nitrogen metabolism, which catalyzes the formation of glutamine from glutamate and ammonium ions produced in a variety of metabolic processes and serves as a nitrogen donor for the biosynthesis of all nitrogen-containing organic compounds important for plant growth and development [138; 139; 140]. The accumulation of toxic levels of ammonium leads to various physiological changes, ammonium toxicity, and lethality [141; 142; 143; 144]. [PERSON] et al. [39] demonstrated that the simultaneous foliar application of _Nr_EO and BASTA alleviated this toxicity by maintaining GS activity, with ammonium concentrations remaining below toxic levels. This protective effect is primarily attributed to NL, the major component of _Nr_EO, although minor components may also contribute to the overall response. Furthermore, [PERSON] et al. [39] highlighted that the cytosolic GS isozymes encoded by the glutamine synthetase 1;1 (_GLNI;1_) and glutamine synthetase 1;3 (_GLNI;3_) genes played a crucial role in _Nr_EO-mediated attenuation of phosphinothricin toxicity. The _GLNI;1_ and _GLNI;3_ genes were activated shortly after treatment, while _GLNI;3_ remained induced even after prolonged exposure. The GS isoforms of _A. thaliana_ consist of GLNI;3 subunits, which have lower electrophoretic mobility, and GLNI;1 and GLNI;2 subunits with higher mobility [145]. The application of BASTA and the combined treatment of BASTA and _Nr_EO resulted in the increased activity of certain low-mobility isoforms. This suggests that the BASTA-induced changes in the expression of _GLNI_ genes may affect the subunit composition of GS isoforms, which affects their abundance and mobility. Furthermore, the combined application of _Nr_EO with BASTA mitigated the harmful effects of BASTA, resulting in the recovery of fresh weight and glucose and fructose content in _A. thaliana_ shoots. In addition, the study of [PERSON] et al. [39] suggests that _Nr_EO could be used as a bioherbicide on BASTA-treated fields to reduce the impact of contamination caused by BASTA residues in the soil on non-target plants. In addition, BASTA may be less effective in fields with medicinal and aromatic plants, such as those with _Nepeta_ species, due to the protective effect of their EOs. [PERSON] et al. [40] further investigated whether the _Nr_EO-mediated reduction of BASTA-induced ammonium toxicity in _A. thaliana_, previously demonstrated during simultaneous foliar application [39], can also be achieved when the herbicide is absorbed via the root. Although BASTA is primarily applied as a foliar spray, its active ingredient PPT has the potential to remain effective in the soil environment. The in vitro system allowed simultaneous exposure of _A. thaliana_ roots to BASTA in a sterile culture medium and _A. thaliana_ shoots to an atmosphere enriched with VOCs of the _Nr_EO. Simultaneous application of BASTA and _Nr_EO mitigated BASTA-induced phytotoxicity in _A. thaliana_ grown in vitro by maintaining physiological and metabolic stability. The combined treatments reduced the negative effects of BASTA on shoot fresh weight and Chl content, indicating the protective role of \(N\)rEO in maintaining plant biomass and photosynthetic potential. \(N\)rEO modulated the metabolic disturbances caused by BASTA, recovering succinic acid content and sugar accumulation.