Arsenic Accumulation in Rice and Probable Mitigation Approaches: A Review

Abstract

According to recent reports, millions of people across the globe are suffering from arsenic (As) toxicity. Arsenic is present in different oxidative states in the environment and enters in the food chain through soil and water. In the agricultural field, irrigation with arsenic contaminated water, that is, having a higher level of arsenic contamination on the top soil, which may affects the quality of crop production. The major crop like rice (Oryza sativa L.) requires a considerable amount of water to complete its lifecycle. Rice plants potentially accumulate arsenic, particularly inorganic arsenic (iAs) from the field, in different body parts including grains. Different transporters have been reported in assisting the accumulation of arsenic in plant cells; for example, arsenate (As V ) is absorbed with the help of phosphate transporters, and arsenite (As III ) through nodulin 26-like intrinsic protein (NIP) by the silicon transport pathway and plasma membrane intrinsic protein aquaporins. Researchers and practitioners are trying their level best to mitigate the problem of As contamination in rice. However, the solution strategies vary considerably with various factors, such as cultural practices, soil, water, and environmental/economic conditions, etc. The contemporary work on rice to explain arsenic uptake, transport, and metabolism processes at rhizosphere, may help to formulate better plans. Common agronomical practices like rain water harvesting for crop irrigation, use of natural components that help in arsenic methylation, and biotechnological approaches may explore how to reduce arsenic uptake by food crops. This review will encompass the research advances and practical agronomic strategies on arsenic contamination in rice crop.

Arsenic Uptake and Accumulation Mechanisms in Rice Species

“…Table 1 shows the reported concentrations of As in rice around the world. All As species can be transferred through the plant cell via specific transporter proteins [14]. The genes involved in transporting As in rice are shown in Table 2.…”

“…Mitra et al [14] expressed that DMA and MMA enter the NIP protein. However, AsIII is more capably taken up by roots than MMA and DMA.…”

“…− becomes the primary species, and at a high pH, HAsO 4 2− is dominant. High soil pH (generally pH 8.5) increases the negative surface charges, such as hydroxyl ions, thereby facilitating the desorption of As from Fe oxides and the resulting mobilisation of As in the root area; these conditions, in turn, increase As accumulation in plants [14].…”

Genomic prediction offers the most effective marker assisted breeding approach for ability to prevent arsenic accumulation in rice grains

“…Alternate wetting and drying of the paddy field during the cropping season is the most effective way to achieve agronomic mitigation. In aerobic soils, the oxidative immobilization of As reduces its phyto-availability and uptake in rice [7]. Application of silicon fertilizer can also reduce the concentration of As in the rice plant [8].…”

Effects of Arsenic, Iron and Fertilizers in Soil on Rice in Cambodia

“…Phosphorus amendments are also often discussed or proposed as a method to overcome arsenic toxicity and block arsenic bioaccumulation (Appendix 3 of the IRDC report). 15 , 34 In Cambodia, it is premature to consider using phosphorus to remediate arsenic contamination. Moreover, the possibility of arsenic treatment with good quality phosphorus fertilizers is uncertain (Appendix 3 of the IRDC report).…”