# Plasma-Activated Water Affects the Antioxidant Contents in Water Spinach
## 3 Results and Discussion
### TP Content  
The TP contents in water spinach of different plasma treatments grown in different soils are shown in Table 3 and Figure 4. For water spinach cultivated in the control soil, significant improvement in TP was observed in each plasma treatment group. PTS + PAW treatment (18.83 \(\pm\) 0.91 mg GAE/g) showed the best improvement at 30.9%, followed by NTS + PAW (17.73 \(\pm\) 0.66 mg GAE/g) and PTS + NTW (16.23 \(\pm\) 1.19 mg GAE/g) compared with NTS + NTW (14.39 \(\pm\) 0.50 mg GAE/g). The improvement under plasma treatment was \begin{table}
\begin{tabular}{l l l l l l} \hline \hline \multirow{2}{*}{**Treatment**} & \multicolumn{2}{c}{**Plant Height (cm)**} & \multirow{2}{*}{} & \multirow{2}{*}{} & \multirow{2}{*}{} & \multirow{2}{*}{} \\ \cline{2-2} \cline{5-6}  & **W1** & & & & & \\ \hline NTS + NTW & 6.4 \(\pm\) 0.37 \({}^{\text{A}}\) & 8.3 \(\pm\) 0.80 \({}^{\text{B}}\) & 9.9 \(\pm\) 0.11 \({}^{\text{CD}}\) & 12.0 \(\pm\) 0.26 \({}^{\text{E}}\) & 15.6 \(\pm\) 1.53 \({}^{\text{F}}\) \\ NTS + PAW & 5.8 \(\pm\) 0.21 \({}^{\text{A}}\) & 7.3 \(\pm\) 0.57 \({}^{\text{B}}\) & 8.8 \(\pm\) 0.19 \({}^{\text{C}}\) & 11.1 \(\pm\) 0.75 \({}^{\text{E}}\) & 15.3 \(\pm\) 1.71 \({}^{\text{F}}\) \\ PTS + NTW & 6.8 \(\pm\) 0.42 \({}^{\text{A}}\) & 8.6 \(\pm\) 0.52 \({}^{\text{B}}\) & 10.7 \(\pm\) 1.16 \({}^{\text{D}}\) & 12.9 \(\pm\) 2.09 \({}^{\text{E}}\) & 15.8 \(\pm\) 4.09 \({}^{\text{F}}\) \\ PTS + PAW & 6.6 \(\pm\) 0.87 \({}^{\text{A}}\) & 8.0 \(\pm\) 0.53 \({}^{\text{B}}\) & 9.6 \(\pm\) 0.40 \({}^{\text{CD}}\) & 11.3 \(\pm\) 0.51 \({}^{\text{E}}\) & 13.4 \(\pm\) 1.16 \({}^{\text{F}}\) \\ \(p\)-value & 0.193 & 0.120 & 0.036 \({}^{\text{*}}\) & 0.277 & 0.622 \\ \hline \hline \end{tabular} Note: Different uppercase letters indicate significant difference (\(p<0.05\)) between groups or treatments, while same uppercase letters do not show significant difference. The data shown are the average values of three repeats. \(W1\)-\(W5\) indicates treatment from week 1 to week 5. NTS: non-treated seed; NTW: non-treated water; PAW: plasma-activated water; PTS: PAW-treated seed.  
\end{table} 
Table 2: The average height of water spinach grown under different treatments in control soil. Figure 3: The average height of water spinach in control soil under different treatments. NTS: non-treated seed; NTW: non-treated water; PAW: plasma-activated water; PTS: PAW-treated seed. Different uppercase letters indicate significant difference between groups or treatments, while same uppercase letters do not show significant difference. significant. This is expected as the PAW reactive species can increase the oxidative stress and elevate the production of antioxidants (e.g., phenolic compounds) in water spinach. The study by [PERSON] [44] revealed that the TP content was increased by 1.4-fold at 0.6 mM Cd treatment than that of the control (from 7.14 to 10.01 mg/g FW). The overproduction of ROS under metal stress must be regulated by the free radical scavenging systems [44]. Here, the treatment of PTS + PAW showed the highest TP content in the control soil, which can be explained as the plant synthesizes various phytochemicals in response to environmental stress [41]. While ROS and RNS from plasma treatment were applied to plants, oxidative stress enhanced the enzymatic systems, and nonenzymatic systems comprise low molecular weight antioxidants and high molecular weight secondary metabolites [45]. Here, water spinach grown in two kinds of contaminated soils was explored to elucidate if plasma treatment affects TP and TF contents. In each pot, the initial Cd concentration of the Cd-added control soil was 18.18-22.28 mg/kg dry weight, whereas the initial Pb concentration of the Pb-added cultivation soil was 2064-2492 mg/kg dry weight. The designed concentrations were three times that of agricultural control levels in farmlands. The TP content of water spinach grown in Cd-added soil decreased in the PTS + NTW treatment group (Table 3 and Figure 4).