## 3 Results and Discussion
### Influence of foliar Ca, Si and Ca + Si Treatments on Grape Phenolic Compounds
\begin{table}
\begin{tabular}{c c c c c} \hline  & **Control** & **Ca** & **Si** & **Ca + Si** \\ \hline _Flavonols_ & & & & \\ Catechin & 29.28 \(\pm\) 2.27 a & 35.94 \(\pm\) 4.41 a & 33.92 \(\pm\) 18.41 a & 24.07 \(\pm\) 4.65 a \\ Epicatechin & 34.33 \(\pm\) 3.82 b & 50.48 \(\pm\) 6.35 c & 17.37 \(\pm\) 3.02 a & 22.28 \(\pm\) 3.30 a \\ Epicatechin-3-galllate & 6.45 \(\pm\) 0.75 a & 7.16 \(\pm\) 1.41 a & 4.18 \(\pm\) 2.29 a & 3.83 \(\pm\) 1.62 a \\ Epigallocatechin & 3.35 \(\pm\) 0.12 a & 5.35 \(\pm\) 1.28 a & 4.47 \(\pm\) 0.43 a & 4.98 \(\pm\) 0.62 a \\ Procyanidin B1 & 8.89 \(\pm\) 0.15 b & 10.05 \(\pm\) 0.84 b & 2.37 \(\pm\) 0.01 a & 2.98 \(\pm\) 0.20 a \\ Procyanidin B2 & 13.93 \(\pm\) 2.75 ab & 20.54 \(\pm\) 2.34 c & 17.50 \(\pm\) 2.09 bc & 11.09 \(\pm\) 1.01 a \\ _Total_ & 96.23 \(\pm\) 8.13 _ab_ & _129.53 \(\pm\) 16.02 b_ & _79.80 \(\pm\) 25.37 a_ & _69.22 \(\pm\) 3.56 a_ \\ \hline _Hydroxybenzoic acids_ & & & & \\ Gallic acid & 3.73 \(\pm\) 0.33 a & 5.06 \(\pm\) 0.27 a & 4.41 \(\pm\) 0.64 a & 5.76 \(\pm\) 1.62 a \\ _Hydroracycline acids_ & & & & \\ _trans-Cafatric acid_ & 4.85 \(\pm\) 0.75 bc & 5.84 \(\pm\) 0.24 c & 4.34 \(\pm\) 0.65 b & 3.05 \(\pm\) 0.42 a \\ _trans-ctis-C_outatric acids & 3.46 \(\pm\) 1.30 ab & 4.07 \(\pm\) 0.23 b & 3.23 \(\pm\) 0.49 ab & 2.17 \(\pm\) 0.02 a \\ _trans-_Fertaric acid & 0.91 \(\pm\) 0.04 a & 1.18 \(\pm\) 0.16 a & 1.00 \(\pm\) 0.03 a & 1.14 \(\pm\) 0.21 a \\ Caffe acid & 0.15 \(\pm\) 0.01 ab & 0.22 \(\pm\) 0.06 b & 0.06 \(\pm\) 0.02 a & 0.09 \(\pm\) 0.02 a \\ _p-_Coumaric acid & 0.06 \(\pm\) 0.01 a & 0.07 \(\pm\) 0.01 a & 0.12 \(\pm\) 0.01 a & 0.29 \(\pm\) 0.20 a \\ Ferulic acid & 0.80 \(\pm\) 0.03 a & 1.09 \(\pm\) 0.46 a & 1.43 \(\pm\) 0.12 a & 1.35 \(\pm\) 0.01 a \\ _Total_ & _10.23 \(\pm\) 2.06 ab_ & _12.45 \(\pm\) 1.09 b_ & _10.18 \(\pm\) 1.08 ab_ & _8.08 \(\pm\) 0.05 a_ \\ \hline _Stilbenes_ & & & & \\ _trans-_Picid & 0.53 \(\pm\) 0.01 a & 0.73 \(\pm\) 0.24 a & 0.85 \(\pm\) 0.07 a & 0.74 \(\pm\) 0.23 a \\ _cis-_Picid & 0.88 \(\pm\) 0.06 a & 1.38 \(\pm\) 0.37 a & 1.13 \(\pm\) 0.00 a & 1.41 \(\pm\) 0.17 a \\ _trans-_Resveratrol & 0.16 \(\pm\) 0.02 a & 0.30 \(\pm\) 0.13 a & 0.22 \(\pm\) 0.06 a & 0.28 \(\pm\) 0.03 a \\ _cis-_Resveratrol & 0.16 \(\pm\) 0.01 a & 0.32 \(\pm\) 0.09 a & 0.40 \(\pm\) 0.06 a & 0.37 \(\pm\) 0.16 a \\ _Total_ & _1.73 \(\pm\) 0.06 a_ & _2.73 \(\pm\) 0.67 a_ & _2.61 \(\pm\) 0.07 a_ & _2.80 \(\pm\) 0.12 a_ \\ \hline \end{tabular} Abbreviations: glc, glucoside; acglc, acetylglucoside; cmglc, _trans-p-_coumaroyllucoside; cfglc, caffeoylsucoside; gleU, glucuronic; gal, galactoside. The phenolic compounds contents are listed with the standard deviation (n = 3). Different letters indicate significant differences between foliar applications (\(p\leq\) 0.05).  
\end{table} 
Table 3: _Cont._control grapes, whereas the foliar application of combined Ca plus Si (Ca + Si) increased the laricitrin-3-glc and isorhamnetin-3-glc concentration in comparison with control grapes (Table 3). Therefore, for flavonoids, the Ca + Si foliar treatment showed a higher effect than the single Ca and Si foliar sprays. It is possible that there was a synergistic effect between Ca and Si in the biosynthesis of this family of phenolic compounds. However, the total flavonoid concentration of grapes did not vary between control and foliar treatments (Table 3). A minor effect or a decrease in some flavonoids was reported for musts and wines of Sauvignon blanc after spraying inorganic Ca and Si salts [37], which is in agreement with the results we obtained for the application of single Ca and Si sprays. Flavanols are related to astringency and bitterness of wines [51], which are mainly due to the occurrence of catechins and tannins. Calcium foliar treatment increased the epicatechin and procyanidin B2 concentration of grapes, in comparison with control and Ca + Si samples (Table 3). In addition, the total flavonoid concentrations of Ca-sprayed grapes was the highest, although this increase was not significant compared to control ones.