## 3 Results
### Concentration and Amount of As  
The concentration and amount of As in plants and phytoliths are shown in Figure 2. _P. australis_ roots accumulate less As under unsaturated conditions (soil water content \(<\) 100%) than saturated conditions (soil water content \(\geq\) 100%) (Figure 2a). \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multicolumn{2}{c}{**Treatments**} & \multicolumn{5}{c}{**Results**} \\ \hline \multirow{2}{*}{\begin{tabular}{c} **Plant** \\ **Species** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Soil Water** \\ **Content** \\ **(mg kg\({}^{-1}\))** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Phylolith** \\ **Content** \\ **(mg kg\({}^{-1}\))** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Water Content** \\ **in Plant Shoot** \\ **(\%)** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Water Content in Plant Root** \\ **Plant Leaf (bar)** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Water Content in Plant Root** \\ **(\%)** \\ \end{tabular} } \\ \hline \multirow{2}{*}{\
\begin{tabular}{c} _Pteris_ \\ _multififida_ \\ \end{tabular} } & 30\% & 114,157.51 a & 64.41 a & \(-\)11.47 & cd & 70.49 & c \\  & 60\% & 104,516.49 a & 69.78 a & \(-\)7.00 & a & 72.06 & c \\ \hline \multirow{4}{*}{
\begin{tabular}{c} _Plragmites_ \\ _australis_ \\ \end{tabular} } & 30\% & 58,642.31 b & 69.61 a & \(-\)13.60 & d & 79.36 & b \\  & 60\% & 137,370.92 a & 67.78 a & \(-\)10.73 & c & 84.32 & a \\ \cline{1-1}  & 100\% & 116,530.55 a & 68.28 a & \(-\)10.40 & bc & 85.08 & a \\ \cline{1-1}  & 130\% & 103,573.27 a & 69.15 a & \(-\)8.87 & ab & 85.78 & a \\ \hline \hline \end{tabular}  
* Different letter in same column indicates significant differences at the 5% level determined via [PERSON]’s test.
* Soil water content indicates percentage of water holding capacity.  
\end{table} 
Table 2: Plant water content water potential and phytolith content *. Figure 1: SEM images and EDS spectra of phytoliths from (**a**) _P. multififida_ at 60% water holding capacity soil and (**b**) _P. australis_ at 60% water holding capacity soil. In the case of _P. multifida_, As concentration in the shoot increased with higher soil water content (Figure 2a). When the soil water contents were 30% and 60% of the water holding capacity, the As concentrations of the _P. multifida_ shoot were 144.54 mg kg\({}^{-1}\) and 528.67 mg kg\({}^{-1}\), respectively. _P. australis_ did not exhibit a tendency in shoot As concentration based on the soil water content. All As concentrations in the shoot of _P. australis_ were significantly lower than those determined for _P. multifida_. In all treatments, As concentration in phytoliths was higher than that in plant shoots (Figure 2a). _P. multifida_ in 60% of water holding capacity had the highest As concentration in phytoliths (1610.74 mg kg\({}^{-1}\)), while the second highest was observed in 30% of water holding capacity (414.70 mg kg\({}^{-1}\)). All phytoliths of _P. australis_ had significantly lower As concentrations than those of _P. multifida_. The range of As in _P. australis_ phytoliths was 41.67-126.54 mg kg\({}^{-1}\). _P. australis_ in 30% of water holding capacity had the highest As concentration in phytoliths than other _P. australis_. Accumulation of As in the shoot and phytolith parts was described as the total amount in a pot (Figure 2b). _P. multifida_ with 60% water holding capacity had the largest amount of As in the plant shoot (698.67 mg pot\({}^{-1}\)), followed by _P. multifida_ with 30% water holding  
Figure 2: Arsenic in _Pteris multifida_ and _Phragmites australis_ as a function of the water content. (**a**) As concentration in plant shoot, phytolith, and roots. As in the shoot and roots was calculated based on plant dry weight, and As in phytoliths was calculated based on phytolith weight. (**b**) The amount of As in plant shoots and phytoliths for each pot. Water content means the percentage of water holding capacity.