## 3 Results
### Composition of Volatile Organic Compounds of Black Cherry Leaves  
Analyses using GC-MS led to the identification of 19 compounds of the total organic volatile fraction from _P. serotina_ fresh leaves and revealed the presence of aldehydes, alcohols, ketones, terpenoids and ester (Table 2). In the case of seven compounds, seasonal variations in their content in volatile fraction were found. The volatiles were exclusively dominated by benzaldehyde. The content of this compound in the total volatile fraction from leaves collected in April and June was comparable, 99.02% and 99.05%, respectively. In aging foliage of black cherry, a significant decrease in content of benzaldehyde to 97.22% was observed.  
\begin{table}
\begin{tabular}{c c c c c c} \hline
**Compound** & **KI exp.** & **KI lit.** & **April (\%)** & **June (\%)** & **August (\%)** \\ \hline
2-ethylfuran & 705 & 703 & 0.0527 \(\pm\) 0.0488 a & 0.0180 \(\pm\) 0.0091 a & 0.0145 \(\pm\) 0.0005 a \\ (E)-2-pentenal & 752 & 755 & 0.0034 \(\pm\) 0.0006 a & 0.0043 \(\pm\) 0.0006 a & 0.0040 \(\pm\) 0.0010 a \\ (E)-3-hexenal & 814 & 811 & 0.3277 \(\pm\) 0.0396 ab & 0.5290 \(\pm\) 0.1837 b & 0.1750 \(\pm\) 0.0320 a \\ (E)-2-hexenal & 857 & 854 & 0.0020 \(\pm\) 0.0020 a & 0.0034 \(\pm\) 0.0032 a & 0.6600 \(\pm\) 0.0330 b \\ 1-hexanol & 867 & 868 & 0.0023 \(\pm\) 0.0006 a & 0.0060 \(\pm\) 0.0056 a & 0.0155 \(\pm\) 0.0025 a \\ (Z)-2-hexen-1-ol & 872 & 870 & 0.0867 \(\pm\) 0.0532 a & 0.0070 \(\pm\) 0.0043 a & 0.3345 \(\pm\) 0.0945 b \\ (\(E\), \(E\))-2.4-hexadien & 915 & 911 & 0.0343 \(\pm\) 0.0396 a & 0.0480 \(\pm\) 0.0745 a & 0.1665 \(\pm\) 0.0115 a \\ benzaldehyde & 965 & 962 & 99.0227 \(\pm\) 0.0416 b & 99.048 \(\pm\) 0.3233 b & 97.2725 \(\pm\) 0.2375 a \\ 2,4-heptadenosine & 1016 & 1013 & 0.0263 \(\pm\) 0.0093 b & 0.0080 \(\pm\) 0.0026 a & 0.0405 \(\pm\) 0.0065 b \\ benzyl alcohol & 1035 & 1036 & 0.0347 \(\pm\) 0.0574 a & 0.0067 \(\pm\) 0.0015 a & 0.3003 \(\pm\) 0.0630 a \\ linalool & 1097 & 1099 & 0.0140 \(\pm\) 0.0017 a & 0.0043 \(\pm\) 0.0038 a & 0.0150 \(\pm\) 0.0050 a \\ \(n\)-nonanal & 1103 & 1102 & 0.0013 \(\pm\) 0.0006 a & 0.0043 \(\pm\) 0.0049 a & 0.0660 \(\pm\) 0.0080 a \\ phenyl ethyl alcohol & 1106 & 1108 & 0.0050 \(\pm\) 0.0026 a & 0.0050 \(\pm\) 0.0010 a & 0.0955 \(\pm\) 0.0175 b \\ (\(E\))-4-decenal & 1194 & 1196 & 0.0050 \(\pm\) 0.0026 a & 0.0067 \(\pm\) 0.0046 a & 0.4650 \(\pm\) 0.0770 a \\ esteroglole & 1198 & 1196 & 0.2190 \(\pm\) 0.3776 a & 0.0103 \(\pm\) 0.0066 a & 0.0000 \(\pm\) 0.0000 a \\ \(\alpha\)-cyanobenzyl alcohol & 1305 & 1302 & 0.0087 \(\pm\) 0.0057 a & 0.0073 \(\pm\) 0.0050 a & 0.1430 \(\pm\) 0.0320 b \\ _cis_-jasmone & 1392 & 1397 & 0.0083 \(\pm\) 0.0035 a & 0.0370 \(\pm\) 0.0225 a & 0.0125 \(\pm\) 0.0025 a \\ (\(E\))-\(\beta\)-caryophyllene & 1413 & 1417 & 0.0710 \(\pm\) 0.0358 a & 0.0787 \(\pm\) 0.0772 a & 0.0240 \(\pm\) 0.0070 a \\ nerylacetone & 1437 & 1435 & 0.0187 \(\pm\) 0.0064 a & 0.1377 \(\pm\) 0.1220 a & 0.0050 \(\pm\) 0.0040 a \\ \hline \end{tabular}
\end{table}
Table 2: Composition of volatile organic compounds (%) identified in fresh _Prunus serotina_ leaves collected in three months of growing season (April, June and August). Data are mean \(\pm\) SD. KI exp.—retention index calculated according to n-alkanes; KI lit.—retention index obtained from NIST17 and Adams [29] database. Significant differences between months marked in rows by different letters (a, b) were estimated by HSD of the Tukey test or Kruskal–Wallis test, \(p\leq\) 0.05; n = 3.  
Figure 1: Effects of volatiles released by _Prunus serotina_ leaves, collected in three months of the growing season (April, June and August), on root length (**A**) and stem height (**B**) of _Pinus sylvestris_ seedlings. Data are mean \(\pm\) SE. Numbers in bars represent % of control. Significant differences between collected dates for each leaf biomass (marked with letters a, b, c) were estimated by the Tukey HSD test at \(p\leq\) 0.05; n = 15.