# The Effects of Plasma-Activated Water on Heavy Metals Accumulation in Water Spinach
## 3 Results and Discussion
### Concentration of Heavy Metals in Water Spinach
The effect of plasma treatment on corn yield was affected by weather and soil quality. The Ar/O\({}_{2}\) plasma affected the wheat plant growth and development by increasing the ascorbate peroxidase (APX) activity in shoots and significantly increased in superoxide dismutase (SOD) activity and the TaSOD expression in the roots of wheat [28]. [PERSON] et al. [29] reported that plasma treatment of 1 min resulted in an improved effect on the total leaf area, shoot, and root lengths, although plasma treatment for 2 min significantly impaired the growth, reducing the total biomass. The high intensity of plasma treatment could cause some changes in the gene expression, inhibiting the growth rates and inducing morphological and physiological differences [29]. According to some studies in the literature, and based on our results, the non-significant results with respect to plant growth following watering with PAW may be affected by metals in the soil, the cultivation environment, and plasma treatment of the seeds. With respect to heavy metals, the presence of Pb in soil reduced the yield of water spinach, while Cd in soil did not affect the yield relative to that in the untreated group (NTS + NTW). The group with the PTS + PAW combination only showed a positive effect in terms of the total weight of the water spinach planted in Pb-soil. In a nutshell, the average height and total weight of the water spinach were affected by the presence of heavy metals in soil. The total weight and the average plant height were restricted by the high concentration of Pb. On the other hand, these restricted parameters can be overcome or improved through plasma treatment. In this study, plasma treatment did not help to improve the product yield of water spinach planted in Cd-added soil, but it was able to increase the average plant height of water spinach after seed treatment. Finally, in the PTS + NTW group, the growth of the water spinach was increased in terms of both total weight and average height compared to that in the control soil. Heavy metals enter the plants through soil uptake and accumulates in different organs, which may reduce plant growth and productivity, while some metabolic processes are also associated with Cd toxicity and its tolerance [30]. A high concentration of Pb can cause several toxic symptoms in plants and may lead to growth retardation in plants, the inhibition of photosynthesis, root blackening, changes in hormonal status, disturbance of mineral and water balance, and other symptoms [31]. Hence, the unsatisfactory plant growth observed in this study may be an effect of heavy metal toxicity. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Treatment**} & \multicolumn{2}{c}{**Cd Concentration**} & \multicolumn{2}{c}{**Pb Concentration**} \\ \cline{2-5}  & **Control Soil** & **Cd-Added Soil** & **Control Soil** & **Pb-Added Soil** \\  & **(mg/kg D.W.)** & **(mg/kg D.W.)** & **(mg/kg D.W.)** & **(mg/kg D.W.)** \\ \hline NTS + NTW & 0.265 & 15.7 & 0.703 & 7.04 \\ NTS + PAW & 0.182 & 12.9 & 0.246 & 7.00 \\ PTS + NTW & 0.215 & 12.1 & 0.284 & 6.94 \\ PTS + PAW & 0.207 & 15.0 & 0.697 & 11.6 \\ \hline \hline \end{tabular} Note: Samples used in the analysis were the mixtures of 3 pots of plants.  
\end{table} 
Table 3: The metal concentrations of water spinach planted in control, Cd-added soil and Pb-added soil (in terms of dry weight). As previously mentioned, the concentration of heavy metals in Cd-added and Pb-added cultivation soil was extremely high, which may have led to the restriction of plant growth. Since the heavy metal concentration used in this study was high and the overall results of plant growth were not consistent with those in some other works in the literature (Table 4), in the future, the plantation environment could be changed and fertilizer could be used to supply some nutrients that could not be provided by PAW in order to support the growth of water spinach. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multicolumn{6}{c}{**A.