## 3 Results
### Staining and Microscopy  
The microscopy observations revealed the differences in the morphological appearance of hyphae. Figure 2 presents the morphology of fungal cells after incubation with cinnamon EO. In the untreated sample, hyphae were gentle and rather thin, as well as having homogeneous cell structure (Figure 2a), while in samples treated with EOs, hyphae became thicker and the internal structure was heterogeneous (Figure 2b-e). With \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**EO**} & \multicolumn{5}{c}{**Effects of Different EO Concentrations on Mycelium Growth**} \\ \cline{2-9}  & \multicolumn{2}{c}{**0.1\%**} & \multicolumn{2}{c}{**1.0\%**} & \multicolumn{2}{c}{**5.0\%**} & \multicolumn{2}{c}{**10.0\%**} \\ \cline{2-9}  & \begin{tabular}{c} **Mycelium** \\ **Size [mm]** \\ \end{tabular} & \begin{tabular}{c} **Growth** \\ **Reduction** \\ **[\%]** \\ \end{tabular} & \begin{tabular}{c} **Mycelium** \\ **Size [mm]** \\ \end{tabular} & \begin{tabular}{c} **Growth** \\ **Reduction** \\ **[\%]** \\ \end{tabular} & \begin{tabular}{c} **Mycelium** \\ **Size [mm]** \\ \end{tabular} & \begin{tabular}{c} **Growth** \\ **Reduction** \\ **[\%]** \\ \end{tabular} & \begin{tabular}{c} **Mycelium** \\ **Size [mm]** \\ \end{tabular} & \begin{tabular}{c} **Growth** \\ **Reduction** \\ **[\%]** \\ \end{tabular} \\ \hline \begin{tabular}{c} **Cinnamon** \\ **Verbena** \\ **Palmarosa** \\ \end{tabular} & \begin{tabular}{c} 50.00 \(\pm\) 0.00 \\ 50.00 \(\pm\) 0.00 \\ 50.00 \(\pm\) 0.00 \\ 50.00 \(\pm\) 0.00 \\ \end{tabular} & 0 & \begin{tabular}{c} 50.00 \(\pm\) 0.00 \\ 48.00 \(\pm\) 1.41 \\ 50.00 \(\pm\) 0.00 \\ 50.00 \(\pm\) 0.00 \\ 50.00 \(\pm\) 0.00 \\ \end{tabular} & 0 & \begin{tabular}{c} 10.50 \(\pm\) 6.36 \\ 48.00 \(\pm\) 1.41 \\ 50.00 \(\pm\) 0.00 \\ 50.00 \(\pm\) 0.00 \\ 50.00 \(\pm\) 0.00 \\ 50.00 \(\pm\) 0.00 \\ \end{tabular} & 0 & \
\begin{tabular}{c} 10.50 \(\pm\) 6.36 \\ 48.00 \(\pm\) 1.41 \\ 49.75 \(\pm\) 0.35 \\ \end{tabular} & 0 &
\begin{tabular}{c} 60.00 \(\pm\) 0.00 \\ 68.00 \(\pm\) 0.00 \\ 10 \\ 1 \\ 1 \\ 49.75 \(\pm\) 1.77 \\ \end{tabular} & 0 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Volatile effect of EOs on the mycelial growth of _F. graminearum_. Figure 1: Volatile effects of different concentrations of palmarosa, verbena and cinnamon EOs on the mycelial growth of _F. graminearum_ on PDA medium (C–control; EO tested concentrations: 0.1%; 1.0%; 5.0%; 10.0%). the increasing concentrations of EOs, the changes became more visible. While in hyphae treated with 0.1% and 1% EO solutions, the heterogeneity of the internal structure was noticeable in the hyphae fragments, fungal cells treated with higher EO concentrations were completely changed. Similar observations were made for the morphology of _F. graminearum_ hyphae treated with verbena EO (Figure S1 in Supplementary Material). Under the light microscope (magnification \(\times\) 400), changes in the morphology of _F. graminearum_ hyphae) treated with palmarosa EO were not observed, due to exhibiting the weakest activity (up to 5% growth reduction for an EO concentration of 10%). The fluorescence method using cFDA and PI was employed to evaluate the viability of fungal cells. The results of cFDA/ PI staining of _F. graminearum_ treated with cinnamon EO are shown in Figure 3. cFDA is a probe that can pass through the membranes of cells [30]. In living cells, it is hydrolys by non-specific esterases to release the fluorescent carboxyfluorescein (green fluorescence). PI is a dye that can only pass through the membranes of damaged or dead cells due to the permeability of the plasma membrane and releases red fluorescence [31]. Great differences were observed between samples treated and untreated with tested EOs. Untreated, control hyphae (Figure 3a,b) show strong green fluorescence demonstrating high viability, with only some single cells stained in red. In the samples treated with EOs, the viability of fungal cells depended on the EO concentration, as shown in the example of cinnamon oil (Figure 3c-i).