# Usage of Si, P, Se, and Ca Decrease Arsenic Concentration/Toxicity in Rice, a Review
### Calcium (Ca) and As
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Selenium Compounds** & **Acronyms** & **Chemical Formula** \\ \hline Inorganic species & & \\ Selenate & Se(VI) & \(\text{H}_{2}\text{SeO}^{4},\text{HseO}_{4}-,\text{SeO}_{4}{}^{2-}\) \\ Selenite & Se(IV) & \(\text{H}_{2}\text{SeO}_{3}{}^{\circ},\text{HseO}_{3}{}^{-},\text{SeO}_{2}\) \\ Elemental Selenium & Se(\({}^{\circ}\)) & Se\({}^{\circ}\) \\ Selenide & Se(-II) & H\({}_{2}\)Se \\ Organic species & & \\ Dimethyl selenide & DMSe & (CH\({}_{3}\))\({}_{2}\)Se \\ Dimethyldiselenide & DMDSe & (CH\({}_{3}\))\({}_{2}\)Se\({}_{2}\) \\ Dimethylseleniumsulfide & & (CH\({}_{3}\))\({}_{2}\)SeS \\ Dimethylseleniumdisulfide & & (CH\({}_{3}\))\({}_{2}\)SeS\({}_{2}\) \\ Selenodi-glutathione & & GSSeSG \\ Selenocysteine & SeC & HSeCH\({}_{2}\)HNH\({}_{2}\)COOH \\ Selenomethionine & SeM & CH\({}_{3}\)Se(CH\({}_{2}\))\({}_{2}\)CHNH\({}_{2}\)\({}_{2}\)COOH \\ Trimethylselenonium & & (CH\({}_{3}\))\({}_{3}\)Se \\ Selenocyanate & & SeCN\({}^{-}\) \\ Selenoproteins & & \\ \hline \hline \end{tabular} Nomenclature is as proposed by [PERSON], [PERSON] [135].  
\end{table} 
Table 3: The list of different species of selenium. soil and water [157, 158]. The research related to the effects of CaO\({}_{2}\) on the accumulation of As in rice plants showed that in the growth in As-contaminated paddy soils, As distribution and concentration in the pore water of all soils tested decreased using CaO\({}_{2}\). In brown rice, treatment of low-level arsenic in soil and CaO\({}_{2}\) increased grain yield and reduced inorganic arsenic concentration; however, in soils enriched with arsenic, the proposed CaO\({}_{2}\) application method is not practical [156]. Another study on the efficacy of exogenous calcium (CaCl\({}_{2}\)) on antioxidant and glyoxalase systems of rice seedlings grown under As stress showed that CaCl\({}_{2}\) in combination with different levels of As significantly decreased As accumulation and plant growth restoration in rice plants. Ca application on arsenic exposed rice seedlings decreased the production of ROS. However, it enhanced activities of ascorbate content (ASA), dehydro-droascorbate reductase (DHAR), glyoxalase I (Gly I), glyoxalase II (Gly II), monohydric ascorbate reductase (MDHAR), superoxide (SOD), catalase (CAT), and glutathione peroxidase (GPX) compared with seedlings that were only exposed to As [159]. Thus, both Ca\({}^{2+}\) and ROS signalling positively correlated under environmental stress [138, 160]. Various studies have shown that the combination of calcium with other elements and compounds significantly affects the levels of arsenic contamination in rice plants. For example, a study showed that the interaction between calcium (Ca\({}^{2+}\)) and melatonin (Mel) effectively increased the endurance of metal toxicity, although the physiological and biochemical mechanisms of that are still unclear [161]. Under arsenic toxicity conditions, Ca\({}^{2+}\) and Mel applications synergistically suppressed the cell death characteristics of the plant (nucleation density and nucleus fragmentation) in stomatal protective cells, ROS formation, and DNA damage in protective roots, leaves, and cells. In addition, the results showed that the use of Mel with Ca\({}^{2+}\) increased the resistance to arsenic toxicity by increasing the enzymes involved in the antioxidant system, the regulation of plasma membrane activity of plasma H\({}^{+}\)-ATPase, and the ascorbate-glutathione pathway [138, 160]. In another experiment, the CF compound including 90% calcium sulphate (CaSO\({}_{4}\)) and 10% ferric oxide (Fe\({}_{2}\)O\({}_{3}\)), significantly decreased the arsenic concentration in soil solution and rice grains [162].