title: Ni2+ toxicity in rice: effect on membrane functionality and plant water content.
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 Ni(2+) 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 Ni(2+) toxicity. Rice plants (Oryza sativa L. cv. Bahia) grown in nutrient medium containing 0.5mM Ni(2+) showed a significant decrease in water content as a consequence of the stress. Addition of Ni(2+) 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 Ni(2+) and the initial resting potential recovered in less than 1h. In the short term (hours), membrane permeability of root cells was not significantly affected by Ni(2+) 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 Ni(2+) treatment. The effects induced by Ni(2+) were not permanent and could be reverted, at least in part, by transferring the plants to a medium without Ni(2+).
authors.affiliation: Departamento de Biología Vegetal, Universitat de València. c/ Dr Moliner 50, Burjassot, Valencia, Spain.
authors.forename: Andreu
authors.initials: A
authors.lastname: Llamas
authors.forename: Cornelia I
authors.initials: CI
authors.lastname: Ullrich
authors.forename: Amparo
authors.initials: A
authors.lastname: Sanz
mesh_terms: D002463:Cell Membrane Permeability / Q000187:drug effects*; D008564:Membrane Potentials; D009532:Nickel / Q000633:toxicity*; D012275:Oryza / Q000737:chemistry / Q000187:drug effects*; D014867:Water / Q000032:analysis*
chemical_list: D014867:Water; D009532:Nickel