## 3 Results
### Effect of Si Foliar Biostimulant Application on Phenolic Content in Olive Leaf
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline  & \multicolumn{4}{c}{**Treatment**} & \multicolumn{4}{c}{**Cultivar**} & \multicolumn{2}{c}{**T \& Cr. Cr.**} \\ \cline{2-10}
**Phenodic Compounds** & **C** & **Si1** & **Si2** & **Si3** & **\(p\) Value** & **IB** & **L** & \(p\) Value** & \(p\) Value** \\ \cline{2-10}
**(mg 100 g\({}^{-1}\) DW)** & **Rain** & 116.63 \(\pm\) 13.13 b & 118.51 \(\pm\) 12.13 b & 137.6 \(\pm\) 11.53 a & **151.17 \(\pm\) 13.82 a & **0.004** & 158.87 \(\pm\) 57.7 b & 100.16 \(\pm\) 52.2 a & **0.001** & 0.963 \\
**Luteolim-7-O-glucoside** & 632.38 \(\pm\) 23.99 b & 628.74 \(\pm\) 28.05 b & 716.21 \(\pm\) 57.45 ab & 758.39 \(\pm\) 70.58 a & **0.008** & 580.3 \(\pm\) 14.18 b & 782.55 \(\pm\) 34.23 a & **0.001** & **0.026** \\
**Apleonin-7-O-glucoside** & 442.8 \(\pm\) 26.4 b & 46.09 \(\pm\) 39.5 b & 54.74 \(\pm\) 21.01 a & 65.73 \(\pm\) 9.11 a & **0.015** & 47.3 \(\pm\) 20.3 b & 58.13 \(\pm\) 52.1 a & **0.003** & 0.195 \\
**Luteolim-4-O-glucoside** & 339.8 \(\pm\) 13.34 b & 31.51 \(\pm\) 0.92 b & 35.81 \(\pm\) 1.5 ab & 37.25 \(\pm\) 22.8 a & **0.034** & 23.71 \(\pm\) 0.79 b & 36.56 \(\pm\) 13.58 a & **0.009** & 0.114 \\
**Luteolim-4-O-glucoside** & 9.44 \(\pm\) 1.7 & 7.48 \(\pm\) 1.3 & 7.83 \(\pm\) 10.56 & 6.89 \(\pm\) 11.88 & 0.244 & 6.03 \(\pm\) 0.69 b & 9.79 \(\pm\) 61.4 b & **0.001** & 0.342 \\
**Apleonin** & 0.02 \(\pm\) 0.02 & 0.21 \(\pm\) 0.1 & 0.1 \(\pm\) 0.08 & 0.24 \(\pm\) 0.22 & 0.615 & 0.07 \(\pm\) 0.04 & 0.22 \(\pm\) 0.12 & 0.254 & 0.681 \\
**Catechin** & 21.83 \(\pm\) 3.35 & 44.29 \(\pm\) 3.3 & 3.29 \(\pm\) 3.52 & 31.99 \(\pm\) 3.44 & 0.157 & 22.86 \(\pm\) 26.4 b & 27.79 \(\pm\) 26.1 & 0.51 \(\pm\) 0.080 \\
**Yrosol** & 18.73 \(\pm\) 20.09b & 15.38 \(\pm\) 15.66 ab & 190.49 \(\pm\) 25.11 a & 25.2 \(\pm\) 32.4 b & **0.019** & 16.14 \(\pm\) 14.38 b & 23.03 \(\pm\) 19.8 a & **0.002** & 0.243 \\
**Verbasociae** & 133.57 \(\pm\) 10.07 & 110.37 \(\pm\) 6.26 & 134.74 \(\pm\) 9.65 & 118.3 \(\pm\) 11.26 & 0.108 & 111.13 \(\pm\) 4.62b & 138.71 \(\pm\) 73.3 a & **0.003** & 0.923 \\
**Oleenpein** & 2422.23 \(\pm\) 136.22 b & 2513.43 \(\pm\) 42.51 b & 304.11 \(\pm\) 13.976 b & 3735.62 \(\pm\) 340.5 a & **0.001** & 303.72 \(\pm\) 178.64 & 238.96 \(\pm\) 228.52 & 0.305 & 0.340 \\
**Oleençion** & 36.24 \(\pm\) 9.65 & 49.9 \(\pm\) 10.35 & 56.36 \(\pm\) 11.64 & 56.86 \(\pm\) 9.29 & 0.441 & 50.56 \(\pm\) 6.43 & 49.12 \(\pm\) 8.14 & 0.886 & 0.152 \\
**Oleençion** & 22.69 \(\pm\) 3.85a & 18.45 \(\pm\) 4.87 b & 110.6 \(\pm\) 2.85 c & 12.49 \(\pm\) 3.58 a & **0.027** & 9.00 \(\pm\) 1.32 b & 23.35 \(\pm\) 28.6a & **-0.001** & 0.516 \\
**Oleençic acid** & 59.91 \(\pm\) 41.05 & 52.03 \(\pm\) 0.6345 & 50.52 \(\pm\) 51.71 & 571.69 \(\pm\) 50.7 & 0.892 & 615.59 \(\pm\) 33.29 a & 481.62 \(\pm\) 29.78 b & **0.006** & 0.144 \\ \hline \end{tabular} Results are expressed as shown \(\pm\) standard errors. Different lowercase letters in a row represent statistically significant differences between mean values for each main defect at \(p\leq 0.05\) obtained by a no-way ANOVA and Tukey’s test.  
\end{table} 
Table 1: The phenolic compound concentration in leaves of two olive cultivars (IB, L) under four different Si foliar fertilisation levels (C, Si1, Si2, Si3). In terms of abundance per polyphenolic species, the most abundant compounds were oleupropein, luteolin-7, and oleanolic acid, followed by verbascoside and rutin with similar concentrations. Other polyphenols were present in much smaller concentrations. PCA analysis for investigated polyphenols has clearly separated the Leccino and Istarska Bjelica genotypes. From Figure 2, it can be noticed that the Leccino cultivar was more affected by Si application and was more spread out in the cartesian plane, while Istarska Bjelica was more rigid in response to Si treatment. The separation of treatments per genotype can also be observed from the graph, as control treatments of both cultivars are separated from Si2 and Si3 treatments.