Selenium addition alters mercury uptake, bioavailability in the rhizosphere and root anatomy of rice (Oryza sativa)

Xun Wang, Nora Fung Yee Tam, Shi Fu, Aray Ametkhan, Yun Ouyang, Zhihong Ye

Research output: Contribution to journalArticlepeer-review

67 Citations (Scopus)

Abstract

Background and Aims Mercury (Hg) is an extremely toxic pollutant, especially in the form of methylmercury (MeHg), whereas selenium (Se) is an essential trace element in the human diet. This study aimed to ascertain whether addition of Se can produce rice with enriched Se and lowered Hg content when growing in Hg-contaminated paddy fields and, if so, to determine the possible mechanisms behind these effects. Methods Two cultivars of rice (Oryza sativa, japonica and indica) were grown in either hydroponic solutions or soil rhizobags with different Se and Hg treatments. Concentrations of total Hg, MeHg and Se were determined in the roots, shoots and brown rice, together with Hg uptake kinetics and Hg bioavailability in the soil. Root anatonmy was also studied. Key Results The high Se treatment (5 μg g-1) significantly increased brown rice yield by 48 % and total Se content by 2·8-fold, and decreased total Hg and MeHg by 47 and 55 %, respectively, compared with the control treatments. The high Se treatment also markedly reduced 'water-soluble' Hg and MeHg concentrations in the rhizosphere soil, decreased the uptake capacity of Hg by roots and enhanced the development of apoplastic barriers in the root endodermis. Conclusions Addition of Se to Hg-contaminated soil can help produce brown rice that is simultaneously enriched in Se and contains less total Hg and MeHg. The lowered accumulation of total Hg and MeHg appears to be the result of reduced bioavailability of Hg and production of MeHg in the rhizosphere, suppression of uptake of Hg into the root cells and an enhancement of the development of apoplastic barriers in the endodermis of the roots.

Original languageEnglish
Pages (from-to)271-278
Number of pages8
JournalAnnals of Botany
Volume114
Issue number2
DOIs
Publication statusPublished - Aug 2014
Externally publishedYes

Keywords

  • Apoplastic barriers
  • Hg bioavailability
  • Oryza sativa
  • Se addition
  • mercury pollution
  • methylmercury
  • rice
  • root endodermis
  • selenium
  • uptake process

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