## 3 Result
### Volatile Free Aroma Composition  
The effects of girdling and foliar fertilization with K on the profiles of free volatile aroma composition of 'Hanxiangmi' grapes are presented in Figure 4 and Table 1. The odor threshold of partial aroma compounds is shown in Table 2. A total of 40 free volatile aroma compounds, including 10 alcohols, 11 terpen, 10 esters, 3 acids and 6 aldehydes were identified by GC-MS analysis. Regarding C6 aldehydes at harvest, (E)-2-hexenal and hexanal were the most abundant volatile aldehydes and were active odorants in all the sample groups due to their low odor threshold, which were accumulated at higher levels in GF and G relative to the control. Similarly, G, F and GF had positive effects on the contents of alcohols compared to the control, with 1-octen-3-ol, 1-heptanol, 2-ethyl hexanol and octanol. Two C6 alcohols, including hexanol and (Z)-3-hexen-1-ol, constituting the majority of the total alcohol concentration. In aromatic compounds, esters contribute greatly to fruity and sweet characters [31; 32]. We found that girdling and foliar fertilization had negative effects on the contents of ethyl butanoate. Ethyl butanoate was one of the most abundant esters in each treatment group. However, it made almost no contribution to the aroma due to its high threshold. Two esters were only detected in the GF group among four treatments, indicating that GF was able to increase the number of ester aromatic compounds. Three acids were detected but made little contribution to aroma owing to their high thresholds. Although octanal, nonanal and benzaldehyde compounds were present only at low levels, these are all aroma active compounds and are expected to contribute significantly to the aroma owing to their low odor thresholds, especially nonanal (1 \(\mathrm{\SIUnitSymbolMicro g/L}\) in water). Figure 3: Effect of girdling and foliar fertilization with K on the concentration of phenolic compounds in ‘Hanxiangmi’ grape skin. The different lowercase letters above the bars indicate a significant difference (\(p<0.05\)). TP, total phenolic concentration (mg/g); PT, polymeric tannin concentration (mg/g); PA, proanthocyanidin concentration (mg/g). \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Compounds**} & \multirow{2}{*}{**DAA**} & \multicolumn{4}{c}{**Treatment**} \\ \cline{3-6}  & & **CK** & **GF** & **G** & **F** \\ \hline \multirow{6}{*}{Nerol} & 49 & N.D & N.D & N.D & N.D \\ \cline{2-6}  & 56 & N.D & 0.0997 \(\pm\) 0.0150 & N.D & N.D \\ \cline{2-6}  & 63 & N.D & 0.4667 \(\pm\) 0.0632 a  & 0.2206 \(\pm\) 0.0349 b  & 0.1361 \(\pm\) 0.0145 b  \\ \cline{2-6}  & 70 & 0.2813 \(\pm\) 0.0079 b  & 0.7899 \(\pm\) 0.0455 a  & 0.2143 \(\pm\) 0.0167 c  \\ \cline{2-6}  & 77 & 0.5610 \(\pm\) 0.0292 b  & 1.1219 \(\pm\) 0.0942 a  & 0.3800 \(\pm\) 0.0530 c  & 0.3708 \(\pm\) 0.0560 c  \\ \hline \multirow{6}{*}{Linalool} & 49 & 0.3869 \(\pm\) 0.0420 a  & 0.2228 \(\pm\) 0.0162 d  & 0.3005 \(\pm\) 0.0280 b  & 0.2858 \(\pm\) 0.0297 b  \\ \cline{2-6}  & 56 & 0.4724 \(\pm\) 0.0551 a  & 0.3936 \(\pm\) 0.0288 a  & 0.4582 \(\pm\) 0.0129 a  & 0.4341 \(\pm\) 0.0560 a  \\ \cline{2-6}  & 63 & 0.9081 \(\pm\) 0.0793 a  & 0.7322 \(\pm\) 0.0318 b  & 0.9479 \(\pm\) 0.0519 a  & 0.7878 \(\pm\) 0.0155 b  \\ \cline{2-6}  & 70 & 0.7761 \(\pm\) 0.1207 b  & 1.1705 \(\pm\) 0.0115 a  & 0.8042 \(\pm\) 0.0933 b  & 1.0628 \(\pm\) 0.0660 a  \\ \cline{2-6}  & 77 & 1.5796 \(\pm\) 0.1439 a  & 1.8683 \(\pm\) 0.1646 a  & 1.2967 \(\pm\) 0.1013 b  & 1.7188 \(\pm\) 0.1798 a  \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Concentrations (\(\mu\)g/L) of terpene compounds determined under girdling and foliar fertilization with K treatments in the pulp juice of 'Hanxiangmi’ table grape at harvest. Figure 4: Concentrations (\(\mu\)g/L) of volatile compounds determined under girdling and foliar fertilization with K treatments in the pulp juice of ‘Hanxiangmi’ table grape at harvest.