Contribution of arbuscular mycorrhizal symbiosis to in vitro root metal uptake: from trace to toxic metal conditions

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Abstract:

This in-vitro study investigated the role of arbuscular mycorrhizal (AM) symbiosis in root metal acquisition and stress tolerance from two experiments using a carrot root-organ culture system, and involving the essential micronutrient zinc as a typical metal contaminant. We demonstrated that the AM symbiosis plays a dual role in root metal acquisition by increasing nutrient uptake via mycorrhizal “enhanced uptake” at low (trace) metal concentrations in the growth medium, but then lessening the uptake through “metal-binding” processes at high (toxic) concentrations. Furthermore, we also observed the relative contribution of hyphal uptake and translocation to roots, which led us to suggest that the enhanced uptake and metal-binding processes likely occur simultaneously and (or) independently. Ultimately, symptoms of metal toxicity toward both the roots and AM fungi at the highest Zn exposure concentrations was observed. From this finding, a critical toxicity burden likely exists arising from conditions ranging from trace to toxic metal extremes.

Dans cette étude in vitro, les auteurs ont examiné le rôle de la symbiose mycorhizienne arbusculaire (AM) dans l'acquisition de métaux et la résistance au stress métallique dans deux expériences, en utilisant le système de culture d'organe racinaire isolé en présence du zinc, un micronutriment essentiel, comme contaminant métallique typique. Ils ont démontré que la symbiose mycorhizienne AM joue un double rôle dans l'acquisition racinaire du métal en augmentant l'absorption du nutriment par une augmentation de l'absorption mycorhizienne, sous de faibles concentrations (traces) du métal dans le milieu de culture, mais diminue l'absorption par la suite par un processus de séquestration aux concentrations élevées (toxiques). De plus, ils ont observé la contribution relative de l'absorption par les hyphes et la translocation aux racines, ce qui conduit les auteurs à suggérer que les processus d'augmentation de l'absorption et de la séquestration surviennent simultanément et/ou indépendamment. Finalement, ils ont observé des symptômes de toxicité du métal envers la racine et le champignon AM aux concentrations en Zn les plus élevées. On déduit qu'il existe vraisemblablement une charge critique de toxicité sous des conditions allant de la présence de traces jusqu'à des extrêmes toxiques du métal.

Document Type: Research Article

Publication date: October 1, 2009

More about this publication?
  • Published since 1929, this monthly journal features comprehensive research articles and notes in all segments of plant sciences, including cell and molecular biology, ecology, mycology and plant-microbe interactions, phycology, physiology and biochemistry, structure and development, genetics, systematics, and phytogeography. It also publishes commentary and review articles on topics of current interest, contributed by internationally recognized scientists.

    Previously published as the Canadian Journal of Botany
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