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Plant and Soil

, Volume 376, Issue 1–2, pp 423–431 | Cite as

Silicon has opposite effects on the accumulation of inorganic and methylated arsenic species in rice

  • Wen-Ju Liu
  • Steve P. McGrath
  • Fang-Jie ZhaoEmail author
Regular Article

Abstract

Background and aims

Rice (Oryza sativa) is a main source of human exposure to inorganic arsenic and mitigation measures are needed to decrease As accumulation in this staple crop. It has been shown that silicon decreases the accumulation of arsenite but, unexpectedly, increases the accumulation of dimethylarsinic acid (DMA) in rice grain. The aim of this study was to investigate why Si increases DMA accumulation.

Methods

Pot and incubation experiments were conducted to investigate how the addition of sparingly soluble silicate gel affected As speciation in the soil solution and the accumulation of different As species in rice tissues.

Results

Silicon addition significantly decreased the concentration of inorganic As (mainly arsenite) but increased the concentration of DMA in both the vegetative and reproductive tissues of rice. Silicon increased the concentration of DMA in the soil solution, whereas autoclaving soil decreased DMA concentration. Less DMA was adsorbed by the soil than arsenate and Si addition significantly inhibited DMA adsorption.

Conclusions

Silicon increased DMA accumulation and decreased arsenite accumulation in rice through different mechanisms. Silicic acid released from the silicate gel increased the availability of DMA for rice uptake by inhibiting DMA adsorption on the soil solid phase or by displacing adsorbed DMA. Although silicic acid also increased the concentration of inorganic As in the soil solution, this effect was much smaller than the inhibitory effect of Si on arsenite uptake by rice roots.

Keywords

Arsenic Arsenic speciation Arsenite Methylated As Rice Silicon 

Notes

Acknowledgments

This research was supported by the Natural Science Foundation of China (41330853, 41073074), the Innovative Research Team Development Plan of the Ministry of Education of China (IRT1256) and a Rothamsted International fellowship. Rothamsted Research is supported by the UK Biotechnology and Biological Sciences Research Council. We thank Professor Jian Feng Ma of Okayama University for providing silica gel.

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Copyright information

© Springer Science+Business Media Dordrecht 2013

Authors and Affiliations

  1. 1.Department of Sustainable Soil and Grassland SystemsRothamsted ResearchHarpendenUK
  2. 2.College of Resources and Environmental ScienceHebei Agricultural UniversityBaodingChina
  3. 3.Laboratory of Plant Nutrition and Fertilization in Low-Middle Reaches of the Yangtze River, Ministry of AgricultureCollege of Resources and Environmental Sciences, Nanjing Agricultural UniversityNanjingChina

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