## 3 Results
### Fatty Acids and Olive Oil Quality Parameters  
Significant effect on fatty acid profiles was more pronounced for the type of cultivar than for the concentration of foliar applied Si, as treatment had significant effect only on the content of palmitic (16:0), palmitoleic (16:1) and linoleic (18:2) acids (Table 4). Figure 3: Multiple comparisons of the effects of treatment (**C**, Si1, Si2, Si3) and cultivar (IB, L) on the contents of tyrosol (**A**), apigenin (**B**), phenolic acids (**C**) and flavonoids (**D**) in olive oil of IB and L cultivars. Different lowercase letters represent statistically significant differences between mean values at \(p<0.05\) obtained by two-way ANOVA and Tukey’s test. Cultivars: IB—Istarska Bjelica, L—Leccino, Treatments: C—untreated control, and Si1—(0.55 g Si/L), Si2—(1.1 g Si/L), Si3—(2.2 g Si/L) applied as potassium silicate solution. Cultivar significantly affected fatty acid profile for all parameters except myristic (14:0), which was not affected by cultivar, treatment or their interaction, and erucic (22:1) acid. Interaction of main factors was significant for palmitic (16:0), palmitoleic (16:1), margaroleic (17:1), and erucic acid (22:1). Content of palmitic acid differed between cultivars. L cultivar had higher values when no Si was applied compared to IB, and their response to Si treatment differed. Si treatment increased mean values of palmitic acid content in IB, but the differences were not significant, and the response in L was ambiguous, with significant differences only between Si2 and Si3 treatments (Figure 4A). Although the interaction terms significant for palmitoleic acid differences between cultivars or between treatments were not pronounced, the only significant differences were between Si2 and Si3 treatment in IB cultivar and Si1 and Si2 treatments in L cultivar (Figure 4B). Treatment-wise, Si2 treatment in L cultivar was significantly lower compared to control. Margaroleic acid content did not change in IB or L cultivars, and the only differences were in contents of margaroleic acid under Si2 and Si3 applications between IB and L, with contents in IB being higher (Figure 4C). Erucic acid contents changed more, but the only significant differences observed were between Si3 treatments of IB and L cultivars, due to high standard errors (Figure 4D). Margaric (17:0), stearic (18:0), oleic (18:1), linolenic (18:3), arachidonic (20:0), gadoleic (20:1), behenic (22:0) and lignoceric (24:0) acids were significantly  
Figure 4: Multiple comparisons of the effects of treatment (C, Si1, Si2, Si3) and cultivar (IB, L) on the contents of fatty acids, namely 16:0 (**A**), 16:1 (**B**), 17:1 (**C**), 22:1 (**D**), in olive oil of IB and L cultivars. Different lowercase letters represent statistically significant differences between mean values at \(p<0.05\) obtained by two-way ANOVA and Tukey’s test. cultivars: IB—Istarska Bjelica, L—Leccino, Treatments: C—untreated control, and Si1—(0.55 g Si/L), Si2—(1.1 g Si/L), Si3—(2.2 g Si/L) applied as potassium silicate solution. affected only by genotype (Table 4). Relative contents of all aforementioned fatty acids were significantly higher in IB cultivar, except for oleic, linolenic and gadoleic acids, which were higher in L cultivar. In cases when the fatty acids' composition was affected by both main factors, the interaction was found to be significant, except for linoleic (18:2), where IB had higher values when looking at factor cultivar while, in terms of treatment, Si3 treatment had a significantly higher value compared to control (Table 4). Olive oil quality parameters were predominantly affected by cultivar (Table 4). Ratios of oleic and linoleic (O/L) and palmitic to linoleic acids (P/L) were insensitive to silicon treatment, whereas cultivar had a significant effect, significantly so in L cultivar, which showed significantly higher values compared to IB cultivar for both parameters (Supplementary Figure S1A,B).