## 4 Discussion
The palmarosa EO has an antifungal activity well documented in the literature, and its biological activity has been studied in the last years. The main constituents of palmarosa EO are geraniol (82%), geranyl acetate (9%), linalool (2%), and _trans_-\(\beta\)-cimene (1%), whereas geraniol is the main constituent associated with its antimicrobial activity [47]. The use of palmarosa EO presents promising results in the control of phytopathogens [23]. It is worth emphasizing that growth inhibition of _F. graminearum_ was greater in wheat and maize grain, especially in EO concentrations of 1% and 0.1%, compared to the volatilization effect on Petri dishes. Moreover, it is worth underlining that the concentration of EOs strongly influenced not only the growth of fungi, but also the mycotoxin biosynthesis. As the results show, the higher concentrations of EOs completely inhibited the growth of fungi, however, the influence of the lower concentration (0.1%) on the fungal growth was also evinced by ERG reduction. The volatilization method showed only the effects of higher doses of EOs. Some authors also pay attention to the dependence of the degree of fungal growth inhibition and mycotoxin level decrease on the EO concentration. [PERSON] et al. [48] used different concentrations of five encapsulated EOs (concentration in rice culture: 1250 \(\mathrm{\SIUnitSymbolMicro g}\)/g of bulk EOs, 1250 \(\mathrm{\SIUnitSymbolMicro g}\)/g of EO nanoemulsions and 125 \(\mathrm{\SIUnitSymbolMicro g}\)/g of 10-fold diluted EO nanoemulsions) to study their efficacy in the inhibition of _F. graminearum_ growth and mycotoxin (DON, 3 ADON, 15 ADON) production. The authors stated that inhibition of mycelium growth and reduction in mycotoxin production were dose-dependent, similarly to the present work. [PERSON] et al. [49] observed that with the increasing dose of _Aframomum danielli_, the degree of fumonisins reduction was higher. Application of 0.25% EO caused an 8% reduction in FB1, while the dose of 10% resulted in 76% reduction. [PERSON] [50] also reported that a reduction in fumonisins was dose-dependent. In this study, it should be noted that the degree of reduction in toxin amount was not always consistent with the degree of ERG reduction. It is especially important to take into account the design of the appropriate amount of EO to apply. While the reduction in ZEA was consistent with the inhibition of ERG biosynthesis, the reduction in DON was not consistent with this parameter. In the research of [PERSON] et al. [51] concerning the antifungal and antimycotoxigenic properties of rosmear EO, the production of aflat was inhibited at concentrations lower than the concentration demonstrating fungistatic activity. The growth of _Aspergillus flavus_ was inhibited with both MIC and MFC at 500 \(\mathrm{\SIUnitSymbolMicro g}\)/mL, while the production of aflat B1 and B2 was reduced after treatment with 250 ug/mL of rosemary EO. Similar results were obtained by [PERSON] & [PERSON] [52] with the essential oils from _Thymus erioclayx_ and _Thymus X-porlock_. Some other authors also reported antimycotoxigenic properties at lower concentrations of EO than the concentration showing fungicidal activity [53, 54]. Microscopic analysis revealed that contact of fungal cells with EOs caused morphological changes, the intensity of which depended on the oil concentration. The deformations of individual hyphae were already visible in a concentration of 0.1% of EO, while concentrations of 1% and above caused a significant decrease in viability, visible in fluorescent staining and cell deformations. Fluorescence-based microscopic methods have been used for viability testing of different bacteria, yeasts, and filamentous fungi [55, 56, 57, 58]. The combination of FDA or cFDA and PI stains is often used to observe the effect of some antimicrobial agents on the microbial cells. For example, [PERSON] et al.