## 3 Results
### Berry Development
Mean values per treatment \(\pm\) SD of the three FACE rings. TA of Riesling showed only one significant probability at the end of 2016 sampling (91%) with a positive difference and a higher TA under eCO\({}_{2}\) conditions (Figure 8). Higher probabilities of Cabernet Sauvignon for TA comparing eCO\({}_{2}\) to aCO\({}_{2}\) during season 2015 (84%-89%) and at the end of 2016 (78%-83%) could not be attested as \"significantly different\" (Figure 9). The development of organic acids during berry ripening is shown in Table 2. The single acids did not reveal a consistent behavior. For instance, the probability of tartaric acid (TAA) was significantly affected by eCO\({}_{2}\) for Riesling during earlier dates in 2015 (3%-6%), but the difference diminished later in season (Figure 8). All TAA values (Table 2) and probabilities (Figure 8) were lower under eCO\({}_{2}\) for Riesling, whereas Cabernet Sauvignon TAA tended to be lower before veraison and became higher values around harvest date in two out of three seasons (Figure 9). Figure 7: Amino acid concentration during ripening periods of the three seasons 2014, 2015, and 2016 for the two varieties Riesling (**a**–**c**) and Cabernet Sauvignon (**d**–**f**) and the two treatments aCO\({}_{2}\) and eCO\({}_{2}\). Letters indicate seasonal development stages veraison (V) and harvest (H). Mean values per treatment \(\pm\) SD of the three FACE rings. Figure 8: Posterior predicted difference (median and 50% HDI) between eCO\({}_{2}\) and aCO\({}_{2}\) for each measurement date from Bayesian generalized linear mixed effects models on berry quality parameters of Riesling. Percentages represent the probability of eCO\({}_{2}\)–aCO\({}_{2}>0\). Filled symbols indicate “significant differences”, if the probability is \(>\)90% (positive difference) or \(<\)10% (negative difference). Figure 2:0 Posterior predicted difference (median and 50% HDI) between eCO\({}_{2}\) and aCO\({}_{2}\) for each measurement date from Bayesian generalized linear mixed effects models on berry quality parameters of Cabernet Sauvignon. Percentages represent the probability of eCO\({}_{2}\)–aCO\({}_{2}>0\). Filled symbols indicate “significant differences”, if the probability is \(>\)90% (positive difference) or \(<\)10% (negative difference). \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**Culivar** & **Date** & **Tartaric Acid (g-1\({}^{\circ}\))** & \multicolumn{3}{c}{**Malic Acid (g-1\({}^{\circ}\))**} & \multicolumn{3}{c}{**Clivic Acid (g-1\({}^{\circ}\))**} & \multicolumn{3}{c}{**Shkilic Acid (mg-1\({}^{\  
Malic acid (MA) of Riesling was also significantly affected at the last two sampling dates in 2016 (91%-97%) and the second last date in 2015 (95%). Cabernet Sauvignon revealed higher MA probabilities for three out of five sampling dates in 2015 (92%-95%). For both cultivars, higher probability values of malic acid were estimated under eCO\({}_{2}\) conditions for the majority of dates within the three seasons. Shikimic acid (SA) and partly citric acid (CA) provided no distinct differences between eCO\({}_{2}\) and aCO\({}_{2}\), and, due to a high variability within treatments, these led to less precise predictions. Cabernet Sauvignon showed a significant difference for SA before veraison in 2015. This was indicated by a low probability (7%) for a negative difference in 2015, which disappeared by the end of season.