Phytomanagement of As-contaminated matrix: Physiological and molecular basis

Elevation of arsenic (As) toxicity is becoming a threat to the environment due to its elevated levels in the soil, water, vegetables, and crops worldwide. Arsenic strongly interacts with iron (Fe), sulfur (S), and phosphorus (P) in agronomic soils. Iron and S strongly bind As in soils and thus reduce As bioavailability for plant uptake. The presence of phosphate [PO4]− 3 triggers As transportation that results in the accumulation of high concentrations of As in rice and other crops. Arsenate [As(V)] is a phosphate [PO4]− 3 analog that enters plant cell via phosphate transport system and interrupts phosphate metabolism. Plants do not have such a mechanism to cope with As(V) uptake in roots. So the applications of P fertilizers to restrict As loading in plants is not a good practice. Sulfur plays a major part in As detoxification by forming arsenite [As(III)] complex with thiol peptides. This complex formation binds As in the roots of plants and resists As translocation. Likewise, Fe also plays a crucial role in the biogeochemical processes of As with Fe oxyhydroxides on the soil and root surface of wetland plants acting as a strong adsorbent for As. Oxidation of Fe(II) and precipitation of Fe(III) on the root surface produce Fe plaques in the rhizosphere of rice. The application of ferrous sulfate also reduces As toxicity to rice, resulting in high grain nutritional yield and decrease grain As loading.