## 3 Results and Discussion  
### Influence of BTH Treatment on the Physicochemical Parameters of Cabernet Gernischt Grapes  
#### 3.1.1 100-Berry Weight and Skin/Berry Ratio  
Cabernet Gernischt grapes underwent two rapid expansions during grape ripening, resulting in an increase in the weight of 100 berries. Specifically, the weight increased by 48.53% and 40.83% at the end-swelling stage (7-9 weeks) and veraison (9-11 weeks), respectively. However, the rate of increase slowed down as the grapes approached full ripening (13-15 weeks). The BTH treatment had a significant effect on the weight of 100 berries, particularly the ripe berries in week 15. The weight of ripe berries (22.79 g) significantly increased by 16.33% compared to the CK (Figure 1A). The weight of grape berries is influenced by factors such as vintage, precipitation, and temperature. Previous studies on the application of BTH to Syrah and Monastrell grapes have demonstrated a significant increase in grape berry weight, which was attributed higher levels of precipitation [19; 25; 28]. In contrast, [PERSON] et al. [22] found that BTH accelerated the rate of absorption of water molecules in grapes. However, if BTH only affects the rate of absorption of water molecules by grapes without the acceleration of cell division and accumulation of primary metabolites within the grapes, no significant difference in weight would be observed between BTH-treated and CK grapes, precisely because we applied BTH during the first phase of rapid growth and development of the grapes. So, this research finding suggests that BTH treatment might increase the berry weight by enhancing cell division, expansion, and metabolite accumulation in grapes, in combination with the analysis of grape phenology and developmental patterns [35].  
BTH treatment had no significant effect on the skin/berry ratio during grape ripening. However, ripe grapes showed an increase of 11.47% compared to the CK (Figure 1B). The rapid expansion of grapes at the initial swelling stage caused a decrease and subsequent increase in the skin/berry ratio before veraison. This trend continued after veraison and until harvest, possibly due to increased skin contents during the second rapid expansion and ripening of the grapes. The weight and skin/berry ratio of grapes can significantly influence the quality of their resultant wine. Thus, the compositional ratios of phenolics, anthocyanins, and tannins in the skin, flesh, and seeds of berries affect leaching and diffusion during wine fermentation. BTH can enhance the accumulation of lignin and its hydroxproline-rich glycoprotein in plant cell walls, leading to the thickening of cell walls or the formation of papillae. Additionally, BTH promotes the deposition of calcium ions and induces the accumulation of calulose at invasive sites [36]. Furthermore, BTH is an SA analog and SA has been found to delay the decline in protocectin and cellulose content, as well as the increase in water-soluble pectin content in grapes. It also delays the rise in activity of cell wall-degrading enzymes, such as polygalacturonase, pectin methylesterase, \(\beta\)-galactosidase, \(\beta\)-glucosidase, and cellulase. Additionally, SA inhibits the expression of _VvPG_, _VvPME_, _Vv\(\beta\)-Gal_, and _Vv\(\beta\)-Glu_, thereby strengthening the skin cell wall [37]. BTH treatment significantly increased the cell wall protein and cellulose content of Monastrell grape berries but showed variety dependence [19]. The increase in cellulose and the thickening of grape skins may affect the efficiency of anthocyanin extraction during winemaking. From the results (Figure 1B), it is evident that BTH, an SA analog, can alter the grape skin/berry ratio of grapes by modulating the composition of the grape skin cell wall.