Arsenic (As), a toxic metalloid, is finding its route to human through intake of As-contaminated water and consumption of food grown on contaminated soil. Rice is the most As-affected crop. Present study is aimed to assess the impact of stabilized orthosilicic acid (a proprietary formulation for plant-available silicon (Si) and earlier used as fertilizer for rice to enhance growth and yield) in reducing the accumulation of As in rice grains. Application of arsenic in the form of arsenate (AsV) and arsenite (AsIII) significantly affected plant growth in a dose-dependent manner. Higher doses of AsV and AsIII (50 and 25 mg L-1 respectively) significantly decreased the yield attributes leading to lower yield. A significant accumulation of As in grain was observed in both AsV- and AsIII-exposed plants in a dose-dependent manner. Arsenic exposure also increased the level of Si in rice grains. Application of Si, either in soil or on leaves (foliar), greatly reduced grain As accumulation (up to 67% in AsV and 78% in AsIII) and enhanced the growth and yield of plants under As stress. The level of thiols and activities of antioxidant enzymes were also enhanced under Si application. Foliar Si application was more effective in increasing grain Si level and reducing grain As than soil Si. The level of other trace elements was also significantly enhanced by Si application irrespective of the presence or absence of As in comparison with control. Arsenic exposure constrained some of the trace elements, such as Zn and Co, which were restored by Si application. Results of the present study showed that the application of currently used Si formulation may effectively reduce grain As level even in highly As-contaminated soil and improve grain quality of rice.
Keywords: Antioxidants; Arsenic; Orthosilicic acid; Rice; Trace element.