## 4 Discussion  
In the natural environment, plant volatile organic compounds (VOCs) released into the atmosphere are directly absorbed on the plant surface and taken up into the leaf via stomatal openings or cuticle diffusion [30]. They also might be transferred to the soil and undergo processes of adsorption, dissolution and degradation, before being taken up by the plant roots [31]. Many volatile compounds emitted by native and alien species have phytotoxic properties and inhibit the growth of coexisting species in their habitat [32]. The results of our laboratory study confirm that this type of interaction is possible in the case of black cherry and Scots pine. The study of [PERSON] and [PERSON] [33] indicated that fresh leaves of _P. serotina_ added to the substrate showed a positive allebotathic effect on the growth of one-year-old _Quercus petraea_ seedlings, another tree species that naturally regenerates in pine forests. [PERSON] et al. [34] also demonstrated that allebotably may be one of the mechanisms underlying the negative impact of invasive tree species on native trees. However, the strongest effect is observed during germination and early seedling growth rather than in the next stages of tree life. In our study, the presence of _P. serotina_ volatile compounds did not have an inhibitory effect on _P. sylvestris_ germination capacity, but they strongly limited the length of seedling roots and contributed slightly to the inhibition of growth of pine seedling stems compared to the control. For comparison, water extracts from black cherry fresh [24] or decomposed leaves [17] marginally affect the germination process, but they strongly inhibit the radicle elongation of newly germinated Scots pine [17]. The work of other authors also indicates that in the case of allebotathic interactions, germination generally is less sensitive than growth of seedlings [35]. In the case of water solutions with potential allebotathic properties, the radicles of the tested species remain in contact with the filter paper, leading to constant absorption of the solution. This may contribute to the greater sensitivity of the seedling root compared to the shoot [36]. Volatiles released from fresh black cherry leaves could be absorbed at the same time by roots and the shoots, which may explain the simultaneous growth response of both parts of the seedlings to the presence of allebotathic \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Parameter** & **Control** & \multicolumn{4}{c}{**Linalool**} \\ \cline{3-6}  & & **5 (\(\upmu\)g mL\({}^{-1}\))** & **10 (\(\upmu\)g mL\({}^{-1}\))** & **25 (\(\upmu\)g mL\({}^{-1}\))** & **50 (\(\upmu\)g mL\({}^{-1}\))** \\ \hline Germination & 95.3 \(\pm\) 0.16 a & 96 \(\pm\) 0.16 a & 91.3 \(\pm\) 0.24 ab & 89.3 \(\pm\) 0.27 ab & 78.7 \(\pm\) 0.32 b \\ capacity (\%) & (100\%) & (101\%) & (96\%) & (94\%) & (83\%) \\ Root length (mm) & 42.8 \(\pm\) 0.89 a & 42.5 \(\pm\) 1.3 a & 29.2 \(\pm\) 1.05 b & 25.9 \(\pm\) 1.36 bc & 18.7 \(\pm\) 0.51 c \\  & (100\%) & (99\%) & (68\%) & (61\%) & (44\%) \\ Stem height (mm) & 50.9 \(\pm\) 0.80 a & 50.4 \(\pm\) 0.90 a & 50.7 \(\pm\) 0.76 a & 45.1 \(\pm\) 1.14 b & 40.3 \(\pm\) 1.37 c \\  & (100\%) & (99\%) & (100\%) & (89\%) & (79\%) \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Effect of linalool used at different concentrations (5, 10, 25 and 50 \(\upmu\)g/mL) on germination and growth parameters of _Pinus sylvestris_ seedlings. Data are mean \(\pm\) SE, numbers in brackets represent % of control. Different letters (a, b, c) following values in rows indicate significant differences for the tested linalool solutions determined in the Tukey HSD test or Kruskal–Wallis test with \(p\leq\) 0.05; n = 15.  
compounds. The most observed effect of most allelochemicals on seedling growth appears to be mediated through a disruption of photosynthesis or respiration [33; 37].