# Usage of Si, P, Se, and Ca Decrease Arsenic Concentration/Toxicity in Rice, a Review
### Phosphorus (P) and As
Competition for Fe plaque or adsorption sites in the soil between PO4 and As (V) via the ligand exchange mechanism increases arsenic bioavailability and solubility in the rhizosphere [88]. Fe plaque plays an essential role in regulating arsenic uptake in rice tissues, and other Fe plaque formation leads to arsenic sequestration at the root surface, leading to decreased arsenic uptake in brown rice [23]. It was observed that the arsenic amount in Fe plaque decreased with increasing concentration of PO4, although increasing arsenic mobility after the addition of PO4 was also reported in several other studies [72,89,90]. It was also reported that sufficient phosphorus leads to several Fe plaque formations in rice roots, while the lack of phosphorus in the solution increases the plaque formation in the roots. Phosphorus low concentrations in the tissues of plants can help increase oxygen transport in rice roots and stimulate the formation of Fe plaque in the roots [91]. Deformation of arsenic species occurs in Fe plaque as the root surface is regulated by microbial processes and the rhizosphere's redox environment, in which As (V) is reduced to As (III) by the arsc gene while by the aioA gene, As (III) is oxidized to As (V). Therefore, it is necessary to boost the Fe plaque formation on the rice root surface, which increases the rice's resistance to arsenic accumulation [92]. Different studies have shown that the essential factor in reducing the absorption of As (V) through the supply of Pi is the competitive absorption of rice roots. In addition, researchers have reported that enhancing the concentration of phosphorus in the nutrient solution reduces the uptake of As (V) through the plant [85,93]. Research has also shown that using high phosphate concentrations in culture solution decreases arsenic-induced damage in rice plants while increasing the amount of As (V) increases the As concentration in roots, leaves, shoots, and seeds. If As concentration decreases with increasing phosphorus [94], the plant's arsenic toxicity may therefore depend more on the ratio of As/P than the total concentration of As. A study in China also described a link between phosphorus and arsenic, and by changing the status of P in the shoots, accumulation of arsenic in rice grains could be reduced [95]. One study found that rice with higher internal phosphorus showed lower toxicity of As (V); therefore, expanding the application of external phosphorus helps decrease the absorption of arsenic and reduce As (V) toxicity symptoms. Two factors control PO4 efficacy on mobility and its uptake of arsenic in rice: (1) Competitionbetween uptake of arsenic and phosphorus in rice roots, and (2) the essential phosphorus role in arsenic transfer from roots to shoots [73]. Both arsenate and phosphate enter the plants through phosphate carriers [97], and in plants, high-affinity transporters of P (Phts/PTs) play an essential role in obtaining phosphorus from the soil. [98]. These P transducers are divided into four subfamilies: Pht1, Pht2, Pht3, and Pht4 [99]. Thirteen Pht1 genes were identified in the genome of rice [100], and between Pht1 genes, OsPht1; 1, 1; 2, 1; 4, 1; 6, 1; 8, 1; 9, and 1; 10 causes the absorption and transfer of phosphorus in rice [101]. OsPT1 is structurally expressed in rice plants for uptake and transport of P under P sufficient conditions [102], and recently it was observed that the performance of OsPht1; 4 recently facilitated uptake and mobility of P in rice [103]. The expression of OsPht1; 6 is involved in the uptake of P under P deficiency conditions in rice roots [104], and likewise, OsPht1; 8 under P-sufficient, and P-deficiency conditions is expressed and regulated in roots [105]. OsPht1; 1, Os Pht1; 4, and OsPht1; are involved in the absorption and transport of As (V), and their expression changes arsenic accumulation in rice [49], and eventually PTs overexpression causes P uptake, although it may also increase uptake of As by rice (Figure 1) [106; 107].