## 3 Results and Discussion
### Enrichment Characteristics of Total Selenium (Se) in Plants  
The Se contents in the plant samples ranged from 50 to 100 ug/kg dry weight, representing the minimum Se intake required by animals and humans. Table 1 presents the test results for Se content in the _G. elata_ samples, with an average Se content of 0.094 mg/kg. To assess the ability of _G. elata_ to absorb and enrich Se compared to other plants, the average Se content in various plants was studied: 16 samples of _Codonopsis_ (\(\sim\)0.017 mg/kg), 60 samples of bamboo shoots (\(\sim\)0.01 mg/kg), 9 samples of cabbage (\(\sim\)0.003 mg/kg), and 457 samples of rice (\(\sim\)0.042 mg/kg) [40]. For further comparison, potatoes and squash grown in Mokriwat soil in Se-rich areas exhibited average Se contents of 78.3 mg/kg and 119.3 mg/kg, respectively [41]. Additionally, wheat cultivated in low-Se soils in the Netherlands, Denmark, and the UK demonstrated average Se contents of 0.028 mg/kg, 0.02 mg/kg, and 0.025-0.033 mg/kg, respectively [42; 43; 44]. These comparisons indicate _G. elata_'s robust Se enrichment capability, laying the groundwork for cultivating Se-rich _G. elata_.  
The bioconcentration coefficient (BCF = Cplant/Csoil) was utilized to assess plants' ability to absorb Se from soil [42; 43; 44]. A larger BCF indicates a stronger ability of the plant to absorb Se from the soil.  
The Nemerow comprehensive pollution index, typically employed to analyze the degree of heavy metal pollution in a region, was introduced to evaluate the degree of soil Se enrichment in _G. elata_ within the study area.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Sample** & **Number** & **Range (mg/kg)** & **Average (mg/kg)** & **S.D.** \\ \hline Soil & 33 & 0.49–3.87 & 1.22 & 0.878 \\ _G. elata_ & 49 & 0.012–0.230 & 0.094 & 0.059 \\ \hline \hline \end{tabular} S.D. = standard deviation.  
\end{table}
Table 1: Results of the selenium (Se) content analysis of the 33 soil samples and 49 _G. elata_ samples.  
The Nemerow comprehensive pollution index was calculated using the following equation:  
\[P_{N}=\sqrt{\frac{P_{AVE}^{2}+P_{MAX}^{2}}{2}}\]  
where \(P_{N}\) indicates the enrichment index of the plants for elements, \(P_{AVE}\) is the average value of an element in the plants, and \(P_{max}\) indicates the maximum value of an element in the plants.  
The analysis of the Se content data in \(G\). _elata_ (Table 1) revealed that the Se enrichment coefficient and enrichment index of \(G\). _elata_ were 11.61% and 0.176, respectively. For comparison, within the same area, _Codonopsis_ exhibits Se enrichment coefficient and enrichment index values of 1.3% and 0.051, bamboo shoots show 0.7% and 0.061, cabbage demonstrates 0.2% and 0.014, and rice presents 3.2% and 0.372, respectively [40]. Furthermore, the Se enrichment coefficient and enrichment index of pumpkins and potatoes grown in Mokorivat are 56% and 36.7%, respectively. In contrast, wheat cultivated in low-Se arable land in the Netherlands, Denmark, and the UK display Se enrichment coefficient values of 3.8-12.7%, 14.3%, and 4.8-6.4%, respectively. Thus, _G. elata_ emerges as a plant with a robust Se enrichment ability.