Journal Article

Understanding the development of roots exposed to contaminants and the potential of plant-associated bacteria for optimization of growth

Tony Remans, Sofie Thijs, Sascha Truyens, Nele Weyens, Kerim Schellingen, Els Keunen, Heidi Gielen, Ann Cuypers and Jaco Vangronsveld

in Annals of Botany

Published on behalf of The Annals of Botany Company

Volume 110, issue 2, pages 239-252
Published in print July 2012 | ISSN: 0305-7364
Published online May 2012 | e-ISSN: 1095-8290 | DOI: http://dx.doi.org/10.1093/aob/mcs105
Understanding the development of roots exposed to contaminants and the potential of plant-associated bacteria for optimization of growth

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  • Ecology and Conservation
  • Evolutionary Biology
  • Plant Sciences and Forestry

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Background and Scope

Plant responses to the toxic effects of soil contaminants, such as excess metals or organic substances, have been studied mainly at physiological, biochemical and molecular levels, but the influence on root system architecture has received little attention. Nevertheless, the precise position, morphology and extent of roots can influence contaminant uptake. Here, data are discussed that aim to increase the molecular and ecological understanding of the influence of contaminants on root system architecture. Furthermore, the potential of plant-associated bacteria to influence root growth by their growth-promoting and stress-relieving capacities is explored.

Methods

Root growth parameters of Arabidopsis thaliana seedlings grown in vertical agar plates are quantified. Mutants are used in a reverse genetics approach to identify molecular components underlying quantitative changes in root architecture after exposure to excess cadmium, copper or zinc. Plant-associated bacteria are isolated from contaminated environments, genotypically and phenotypically characterized, and used to test plant root growth improvement in the presence of contaminants.

Key Results

The molecular determinants of primary root growth inhibition and effects on lateral root density by cadmium were identified. A vertical split-root system revealed local effects of cadmium and copper on root development. However, systemic effects of zinc exposure on root growth reduced both the avoidance of contaminated areas and colonization of non-contaminated areas. The potential for growth promotion and contaminant degradation of plant-associated bacteria was demonstrated by improved root growth of inoculated plants exposed to 2,4-di-nitro-toluene (DNT) or cadmium.

Conclusions

Knowledge concerning the specific influence of different contaminants on root system architecture and the molecular mechanisms by which this is achieved can be combined with the exploitation of plant-associated bacteria to influence root development and increase plant stress tolerance, which should lead to more optimal root systems for application in phytoremediation or safer biomass production.

Keywords: Abiotic stress; metals; organic contaminant; plant-associated bacteria; cadmium; copper; zinc; ‘2,4-DNT’; root morphology; endophyte; green revolution; systemic response

Journal Article.  10065 words.  Illustrated.

Subjects: Ecology and Conservation ; Evolutionary Biology ; Plant Sciences and Forestry

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