# Usage of Si, P, Se, and Ca Decrease Arsenic Concentration/Toxicity in Rice, a Review
### Selenium (Se) and As  
Selenium is widely spread in the earth's crust and is mainly related to sulphide minerals [108]. Until 1957, Se was known as a toxic element [109], and after that, the positive effect of selenium on human and animal health was discovered [110]; however, no evidence shows that Se is an essential element for plants [111]. Nevertheless, selenium has a vital effect on thyroid hormone metabolism, cellular metabolism, antioxidant functions, immune responses, and other minerals' uptake and accumulation regulation in humans [112]. Moreover, Se deficiency is related to health disorders, including reduced fertility, oxidative stress, accelerated aging, decreased immune function, and cancer risk increment [113]. Selenium is specifically present as seleno-L-cysteine in a multitude of selenoproteins [114]. These proteins are crucial in repairing oxidized residues and modulating oxidative stress through natural biological oxidant detoxification [115; 116]. It has been appraised that between five hundred million and one billion of the world's population suffer from Se deficiency, but on the other hand, selenium is toxic in high concentrations, so the line between the toxicity of Se to humans and Se-deficiency is critical [113]. Plants are the primary source of Se for people worldwide [105], and recently, selenium fertilizers have been used to enhance Se in plant's edible parts [117]. Selenium comes in two forms: organic and inorganic (Table 3). Soils contain inorganic selenite and selenate that accumulate in plants and are converted to organic forms [118]. The optimal dose of Se in plants has not \begin{table}
\begin{tabular}{c c c} \hline \hline
**Equation** & **Isotherm** & **Equation \#** \\ \hline \(q_{e}=\)\(K_{f}\)\(C\)\(\frac{1}{\pi}\) & Freundlich nonlinear & (1) \\ \(\log\)\((q_{e})\)\(=\)\(\log K_{f}+\frac{1}{\pi}\) logC & Freundlich linear & (2) \\ \(\frac{C_{e}}{q_{e}}=\frac{1}{q_{e}}\)\(C_{e}+\frac{1}{K_{e}q_{e}}\) & Langmuir linear 1 & (3) \\ \(\frac{1}{q_{e}}=(\frac{1}{K_{e}q_{e}})\)\(\frac{q_{e}}{K_{e}}\) & Langmuir linear 2 & (4) \\ \(q_{e}=q_{m}-\)\((\frac{1}{K_{e}})\)\(\frac{q_{e}}{C}\) & Langmuir linear 3 & (5) \\ \(\frac{q_{e}}{C_{e}}\)\(=\)\(K_{g}\)\(q_{m}-\)\(K_{a}\)\(q_{e}\) & Langmuir linear 4 & (6) \\ \(q_{e}=\)\(\frac{Q_{h}\)\(K_{l}\)\(C_{e}\)\(}{1+K_{l}\)\(C_{e}\)\(}\) & [PERSON] nonlinear & (7) \\ \(R_{L}\)\(=\)\(\frac{1}{\Gamma+K_{l}\)\(C_{0}}\) & & (8) \\ \(q_{e}\)\(=\)\(\frac{K_{e}}{1+\delta_{e}\)\(C_{0}^{l}}\) & [PERSON] nonlinear & (9) \\ \(\log\)\((K_{r}\frac{C_{e}}{q_{e}}-1)\)\(=\)\(\beta\)\(\log\)\((C_{8})\)\(+\) in \((\alpha_{r})\) & [PERSON] linear & (10) \\ \hline \hline \end{tabular} Nomenclature is as proposed by [PERSON] [96].  
\end{table} 
Table 2: Freundlich, Langmuir, and Redlich-Peterson Equations. been determined, and selenium is thought to be suitable for plants that can accumulate it in high concentrations [119]. Selenium incites the growth of plants at low doses via dry matter yield addition, particularly in sulphur deficiency [120]. Also, low levels of selenium neutralize the harmful efficacies of many environmental stresses. Research has shown that low Se concentrations in plants act as antioxidants, but selenium brings oxidative damage to plant tissues in excessive doses [117; 121]. However, Se can positively affect appropriate properties, like enhancing growth, increasing antioxidant activities capacity, increasing starch accumulation, reducing lipid peroxidation, and oxygen reactive species [122]. Therefore, Se increases essential elements, nutritional value, grain yield, and resistance to the stress of metals [123]. Several reports have shown that the external supply of Se has a positive efficacy on toleration to abiotic stress and plant growth [124]. Previous studies have reported that Se (IV) is transported to plant roots via phosphate and silicon transporters [123], and Se (VI) is transported to plant roots via sulphate transporters and may be inhibited by phosphate [125].