Root Elongation Method for the Quality Assessment of Metal-Polluted Soils: Whole Soil or Soil-Water Extract?

Root elongation method may be implemented using two internationally accepted protocols: exposing plants to either soil-water extract or whole soil. But which of the two protocols is more suitable for root elongation analysis undertaken for the quality assessment of metal-polluted soils? Soils were sampled at various distances from the site of the Middle Urals Copper Smelter located in Russia. White mustard was used as a bioindicator. We observed considerable differences in root elongation under the two protocols. In plants grown in whole soil, root length inversely correlated with pollution index, but in soil-water extract, metal concentrations had no effect on root length. Nutrient and metal concentrations in the soil-water extract were not buffered, due to the absence of the solid soil phase. It is for this reason that in highly polluted soils, root growth was greater in soil-water extracts rather than in whole soils, whereas in background soils (in the absence of toxicity), root growth was greater in whole soils compared with soil-water extracts. The quantity, intensity, and capacity factors are a plausible explanation for the differences in root length between the two protocols. The soil-water extract does not represent actual soil with respect to the desorption-dissolution reactions that take place between the soil solid phase and the soil solution. For this reason, whole soil protocol should be used for measuring root elongation given that only under this protocol, direct contact between metal-polluted soil and test organisms correctly replicates the risks inherent in the actual soil habitat. © 2020, Sociedad Chilena de la Ciencia del Suelo.

Prudnikova E.V.1 , Neaman A. 2 , Terekhova V.A.1, 3 , Karpukhin M.M.1 , Vorobeichik E.L.4 , Smorkalov I.A.4 , Dovletyarova E.A. 5 , Navarro-Villarroel C.6 , Ginocchio R.7, 8 , Peñaloza P.9
Springer Science and Business Media Deutschland GmbH
  • 1 Faculty of Soil Science, Lomonosov Moscow State University, Moscow, Russian Federation
  • 2 Instituto de Ingeniería Agraria y Suelos, Facultad de Ciencias Agrarias y Alimentarias, Universidad Austral de Chile, Valdivia, Chile
  • 3 Institute of Ecology and Evolution, Russian Academy of Sciences, Moscow, Russian Federation
  • 4 Institute of Plant and Animal Ecology, Ural Branch of the Russian Academy of Sciences, Ekaterinburg, Russian Federation
  • 5 Department of Landscape Design and Sustainable Ecosystems, RUDN University, Moscow, Russian Federation
  • 6 Instituto de Estadística, Universidad de Valparaíso, Valparaíso, Chile
  • 7 Center of Applied Ecology and Sustainability (CAPES), Pontificia Universidad Católica de Chile, Santiago, Chile
  • 8 Facultad de Agronomía e Ingeniería Forestal, Pontificia Universidad Católica de Chile, Santiago, Chile
  • 9 Escuela de Agronomía, Pontificia Universidad Católica de Valparaíso, Quillota, Chile
Ключевые слова
Aqueous extracts; Ecotoxicity; Inhibition; Middle Urals; Phytotoxicity; Toxicity
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