## 3 Results and Discussions
### Histo-Anatomical Aspects of the Lemon Balm
#### 3.4.3 Internal Structure of the Leaves  
In the cross section, the main rib is highlighted on the inferior surface and contains a single vascular bundle (Figure 6a,b). The epidermal cells (from the upper and lower epidermis) are elongated \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Vegetative** & \multicolumn{4}{c}{**Treated Plants (Mean \(\pm\) SD)**} & \multicolumn{2}{c}{**Control Plants**} \\ \cline{3-6}
**Organs** & **SBPE1** & **SBPE2** & **BBPE1** & **BBPE2** & **(Mean \(\pm\) SD)** \\ \hline
**Root** & Secondary xylem area (\%) & 44.22 \(\pm\) 4.51 b  & 45.88 \(\pm\) 6.41 b  & 49.84 \(\pm\) 51.2 a  & 46.82 \(\pm\) 57.4 b  & 43.04 \(\pm\) 5.12 b  \\ \hline \multirow{4}{*}{**Stem**} & Vascular bundles area (\%) & 13.81 \(\pm\) 2.02 b  & 13.54 \(\pm\) 1.44 b  & 15.9 \(\pm\) 1.51 a  & 13.1 \(\pm\) 1.12 b  & 12.72 \(\pm\) 1.74 b  \\ \cline{2-6}  & Scherechyma cap area (\%) & 1.11 \(\pm\) 0.17 a  & 0.85 \(\pm\) 0.09 b  & 0.89 \(\pm\) 0.11 b  & 0.88 \(\pm\) 0.11 b  & 0.88 \(\pm\) 0.11 b  & 0.88 \(\pm\) 0.11 b  & 0.91 \(\pm\) 0.09 b  \\ \cline{2-6}  & Colenchin area (\%) & 6.95 \(\pm\) 0.94 a  & 6.21 \(\pm\) 0.82 b  & 5.81 \(\pm\) 1.18 b  & 5.71 \(\pm\) 1.04 b  & 5.74 \(\pm\) 1.11 b  \\ \cline{2-6}  & Number of vascular bundles & 5.45 \(\pm\) 1.42 b  & 5.54 \(\pm\) 1.19 b  & 6.85 \(\pm\) 1.04 a  & 5.21 \(\pm\) 1.55 b [FONOTE:b]Footnote b: footnotemark: [ENDFOOTNOTE] & 5.01 \(\pm\) 1.41 b  \\ \hline \multirow{4}{*}{**Leaf**} & Leaf lamina thickness (mm) & 0.851 \(\pm\) 0.054 a  & 0.842 \(\pm\) 0.047 a  & 0.872 \(\pm\) 0.027 a  & 0.79 \(\pm\) 0.023 a  & 0.82 \(\pm\) 0.042 a  \\ \cline{2-6}  & Vascular bundles area in the & & & & & \\  & main string (\%) & 15.24 \(\pm\) 1.56 b  & 16.12 \(\pm\) 1.09 b  & 17.42 \(\pm\) 1.47 a  & 15.87 \(\pm\) 2.15 b  & 14.98 \(\pm\) 1.72 b  \\ \hline \hline \end{tabular}
\begin{tabular}{c} SBPE 1—spruce bark polyphenonic extract at a concentration of 0.25 g bark/100 mL water, SBPE 2—spruce bark polyphenonic extract at a concentration of 0.5 g bark/100 mL water, BBPE 1—beech bark polyphenonic extract at a concentration of 0.25 g bark/100 mL water, BBPE 2—beech bark polyphenonic extract at a concentration of 0.5 g bark/100 mL water. Different letters indicate significant differences compared with the control (\(p\leq 0.05\), Mann-Whitney test). \\ \end{tabular}
\end{table} 
Table 2: The microscopic characteristics of vegetative organs in case of treated and control lemon balm plants. Figure 5: The internal structure of the stem: (**a**) general aspect (control), (**b**) general aspect (BBPE 1). tangentially, which is larger on the superior surface. The two types of hairs, which are vectorial and secretory (the latter containing a gland made out of single or multiple cells), had an irregular disposition. The mesophyll is split into palisade parenchyma and spongy tissue. Thus, the foliar blade has a bifacial hetero-facial structure. After examining the internal structure of the leaves, no significant differences were found in comparison with the control samples (Table 2). The only difference that can be observed is the BBPE 1 (Figure 7a,b), which is a less developed vascular bundle in the main string when compared to the control samples and to the other variants. Moreover, the lignification process is more intense such as in the stem. Previous studies provide information on the stimulatory or inhibitory role of the polyphenolic compounds regarding the germination process and biomass accumulation. The authors conclude that global extracts induce similar effects to auxins and cytokins on plant growth [13; 15]. The results of this work confirm the previous findings. Thus, a higher number of grown plants for the variants treated with SBPE was observed. The final analysis shows a greater efficiency for the variants treated with BBPE in development except the roots, of which biomass and elongation were inhibited in the case of both extracts.