Ni2+ toxicity in rice: Effect on membrane functionality and plant water content

  • Llamas A
  • Ullrich C
  • Sanz A
  • 39

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Abstract

The heavy metal nickel is an essential mineral trace nutrient found at low concentrations in most natural soils. However, it may reach toxic levels in certain areas and affect a number of biochemical and physiological processes in plants. Wilting and leaf necrosis have been described as typical visible symptoms of Ni2+ toxicity. The plasma membrane (PM) of root cells constitutes the first barrier for the entry of heavy metals but also a target of their toxic action. This work studies the relationship between disturbances of membrane functionality and the development of the typical symptoms of Ni2+ toxicity. Rice plants (Oryza sativa L. cv. Bahia) grown in nutrient medium containing 0.5 mM Ni2+ showed a significant decrease in water content as a consequence of the stress. Addition of Ni2+ to the solution bathing the roots induced a concentration-dependent PM depolarization but the activity of the PM-H+-ATPase was not inhibited by the presence of Ni2+ and the initial resting potential recovered in less than 1 h. In the short term (hours), membrane permeability of root cells was not significantly affected by Ni2+ treatments. However, in the long term (days) a drastic loss of K+ was measured in roots and shoots, which should be responsible for the changes in the water content measured, since stomatal conductance and the transpiration rate remained unaffected by Ni2+ treatment. The effects induced by Ni2+ were not permanent and could be reverted, at least in part, by transferring the plants to a medium without Ni2+. ?? 2008 Elsevier Masson SAS. All rights reserved.

Author-supplied keywords

  • Membrane permeability
  • Nickel toxicity
  • Oryza sativa
  • Stress alleviation
  • Water content

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Authors

  • Andreu Llamas

  • Cornelia I. Ullrich

  • Amparo Sanz

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