# Identification and Allelopathy of Green Garlic
## 2 Results
### Effect of Green Garlic Volatiles and DADS on Cucumber ROS and Antioxidant Activity  
2.1 Effect of Green Garlic Volatiles and DADS on Cucumber ROS (O\({}_{2}\)\({}^{\bullet}\)- and H\({}_{2}\)O\({}_{2}\))  
Figure 3A showed the results of histological observation of H\({}_{2}\)O\({}_{2}\) in cucumber leaves stained by DAB dye. Compared with the control groups, the colors of dyed cucumber leaves gradually turned much darker with the increasing concentrations of green garlic volatiles and DADS (Figure 3A).  
\begin{table}
\begin{tabular}{c} Methyl \\ properly \\ disulfide \\ \end{tabular} } & \multirow{2}{*}{0} & \multirow{2}{*}{-} \\  & & & & & & & \\ \hline \hline \end{tabular}
\end{table}
Table 1: Total sulfur compounds of green garlic volatile compounds among different collecting methods.  
Figure 2: The biological test and its results of green garlic volatiles and DADS on cucumber leaf. (**A**) effect of green garlic (0.0, 1.0, 2.0, 3.0, 5.0 g) volatiles on cucumber leaf color and structure. (**B**) effect of DADS (0, 0.5, 1, 2, 3, 5, and 10 mmol/L) on cucumber leaf color and structure. Five leaves from 5 plants were used for each treatment.  
This suggested that green garlic volatiles and DADS led to an increasing H\({}_{2}\)O\({}_{2}\) content at histological levels. After 10-days of co-culture with green garlic, the O\({}_{2}\)*- contents of treated cucumber leaves were significantly lower that of control (\(p<0.05\)). Similarly, the O\({}_{2}\)*- contents of cucumber leaves under 1 mmol/L DADS treatment was also lower than that of control group (Figure 3B). The H\({}_{2}\)O\({}_{2}\) content in cucumber leaves exhibited a rising trend with the increase of the concentration of green garlic volatiles. Besides, the H\({}_{2}\)O\({}_{2}\) contents in cucumber leaves of all green garlic treatments and DADS were significantly higher than that of control (\(p<0.05\)), which were consistent with the histological observations of H\({}_{2}\)O\({}_{2}\) in cucumber leaves (Figure 3A).  
.2.2 Effect of Green Garlic Volatiles and DADS on Cucumber Antioxidant Substances (MDA, GSH and ASA)  
The MDA content of cucumber leaves co-cultured with 6-bulbs of green garlic was significantly lower than that of control (\(p<0.05\)) (Figure 3D), while, that for co-cultures with 12- and 18-bulbs of green garlic the MDA content was significantly higher than the control group (\(p<0.05\)) (Figure 3D). When cucumber seedlings were treated with DADS, the MDA content of cucumber leaves was also significantly lower than that of control (\(p<0.01\)) which was consistent with the treatment co-cultured  
Figure 3: Effect of green garlic volatiles and DADS on cucumber ROS, antioxidant substance and antioxidant enzymes activity. (**A**) Histological observation of H\({}_{2}\)O\({}_{2}\) in cucumber leaves that stained by DAB dye. (**B**,**C**), effect of green garlic volatiles and DADS on cucumber ROS (O\({}_{2}\)*– and H\({}_{2}\)O\({}_{2}\)); (**D**–**F**), effect of green garlic volatiles and DADS on cucumber antioxidant substance content (MDA, GSH and ASA); (**G**–I**), effect of green garlic volatiles and DADS on cucumber antioxidant enzyme activity (SOD, CAT and POD). * \(p<0.05\); ** \(p<0.01\); ANOVA, followed by Tukey test and \(t\)-test. Data are means \(\pm\) standard errors (\(n=3\) for (**B**,**C**), three biological replicates).  
with 6-bulbs of green garlic (Figure 3D). The GSH content had an increasing trend with the increasing number of bulbs of green garlic. The GSH contents of 6-bulb green garlic and DADS treatment were both significantly lower than that of control (\(p<0.05\)), but the treatments with 12- and 18-bulbs of green garlic were higher than that of control (Figure 3E). The ASA content in cucumbers treated with green garlic bulbs and DADS were consistently lower than that of control (Figure 3F).