# Plasma-Activated Water Affects the Antioxidant Contents in Water Spinach
## 3 Results and Discussion
### TF Content
\begin{table}
\begin{tabular}{l l l l} \hline \hline \multirow{2}{*}{**Treatment**} & \multicolumn{2}{c}{**TF Content (mg QE/g DM) of the Water Spinach Planted in**} & \multirow{2}{*}{\(p\)**-Value**} \\ \cline{2-2} \cline{4-4}  & **Control Soil** & **Cd-Added Soil** & & \\ \hline NTS + NTW & 7.95 \(\pm\) 1.61 \({}^{\text{A}\text{a}}\) & 9.20 \(\pm\) 0.13 \({}^{\text{Ba}}\) & 9.21 \(\pm\) 0.34 \({}^{\text{Fa}}\) & 0.257 \\ NTS + PAW & 9.00 \(\pm\) 0.86 \({}^{\text{Ab}}\) & 9.99 \(\pm\) 0.32 \({}^{\text{CDb}}\) & 9.69 \(\pm\) 0.07 \({}^{\text{Rb}}\) & 0.145 \\ PTS + NTW & 9.24 \(\pm\) 0.37 \({}^{\text{Ad}}\) & 9.54 \(\pm\) 0.27 \({}^{\text{BCd}}\) & 7.25 \(\pm\) 0.04 \({}^{\text{Ec}}\) & \textless{}0.001 *** \\ PTS + PAW & 9.77 \(\pm\) 0.16 \({}^{\text{Af}}\) & 10.53 \(\pm\) 0.44 \({}^{\text{Df}}\) & 7.60 \(\pm\) 0.82 \({}^{\text{E}}\) & \textless{}0.05 \({}^{\text{*}}\) \\ \(p\)-value & 0.194 & \textless{}0.01 ** & \textless{}0.001 *** & \\ \hline \hline \end{tabular} Note: Different uppercase letters indicate the significant difference between plasma treatment, while different lowercase letters indicate the significant difference between cultivation soil (\({}^{*}p<\) 0.05, \({}^{**}p<\) 0.01, *** \(p<\) 0.0001). Samples used in the analysis are the mixtures of three pots of plants and the data shown are the average analysis values of three repeats. NTS: non-treated seed; NTW: non-treated water; PAW: plasma-activated water; PTS: PAW-treated seed.  
\end{table} 
Table 4: Comparison of TF content in water spinach with different plasma treatments grown in different soil of Phase-1 pot experiment. Figure 5: Comparison of TF content in water spinach with different plasma treatments grown in different soil. NTS: non-treated seed; NTW: non-treated water; PAW: plasma-activated water; PTS: PAW-treated seed. Different uppercase letters indicate the significant difference between plasma treatment, while different lowercase letters indicate the significant difference between cultivation soil. The usage of PAW only showed a 15.5% increase in TF content in water spinach compared to that of RO water. With the addition of fertilizer, the TF content elevated to 33.6%. The use of PAW or fertilizer can significantly increase TF content in water spinach, and it has a synergistic effect when both are used simultaneously. Although the TP content among the four treatments did not show a significant difference (as shown in Table 5 and Figure 6), the results of the Phase-2 pot experiment were different from those of the Phase-1 pot experiment. In summary, for the Phase-1 pot experiment, TP content can be elevated by plasma treatment of the water spinach grown in cultivation soil. However, plasma treatment of water spinach inhibited the TP content, especially in the Pb-added soil. Meanwhile, plasma treatment also showed a trend to inhibit the TF content of water spinach grown in the Pb-added soil. In the Phase-2 pot experiment, following fertilizer application, the TF of water spinach was not improved by the enrichment of the soil nutrient, which is RO + Fert, containing a greater amount of TF than RO only, and PAW + Fert showed a greater amount than the PAW only. Overall, the particular findings in certain cultivation conditions do not agree to what is already known, that the TP and TF contents of plants can increase under heavy metal stress. Therefore, we suggest further studies investigating the effect of PAW, as well as its synergistic action with fertilizer, on the TP and TF contents of water spinach under heavy metal stress to understand the role of PAW in this phenomenon.