Published online 7 November 2005
Published in J Environ Qual 34:2156 (2005)
DOI: 10.2134/jeq2005.0002in
© 2005 American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America
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Rhizosphere Conference
Rhizosphere Conference
W.W. Wenzel
University of Natural Resources and Applied Life Sciences, Vienna
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Introduction
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THE INTERNATIONAL CONFERENCE "Rhizosphere 2004: Perspectives and Challenges—A Tribute to Lorenz Hiltner" was held in Munich from 12–17 Sept. 2004. It was initiated as a main activity of COS, an intergovernmental framework for European Cooperation in the field of Scientific and Technical Research (COST). COST Action 631 (http://www.rhizo.at/cost631) was a European initiative in 2004 to create a network of scientists from all disciplines involved in research of the plant root–soil interface, which was given the name rhizosphere by Hiltner (1904), who began some of the original work on this topic more than 100 years ago. Extended abstracts of keynote presentations and abstracts of other contributions were recently published in the form of conference proceedings (Hartmann et al., 2005). This special submission section assembles selected papers from the session "Fate and Management of Pollutants."
The session was organized to provide an overview on the role of the rhizosphere in terms of the behavior of both organic and inorganic pollutants in soil–plant–microbe systems, and to explore the prospects of manipulating the rhizosphere for control of pollutants and remediation of contaminated soils.
Whereas nutrients have been the focus of rhizosphere research from the very beginning, with numerous examples even before the days of Hiltner (1904), pollutants have only more recently been addressed as a consequence of the increasing awareness of environmental problems.
Several oral presentations emphasized the rich opportunities to use or manage the rhizosphere environment for the degradation of organic pollutants. Contaminants addressed included polycyclic aromatic hydrocarbons (PAH) and organopesticides—rather persistent compounds with complex pathways of degradation. The inherent complexity of the processes controlling biodegradation of such compounds in the rhizosphere was pointed out in several contributions. The rhizosphere effects involved are still hardly explored and include the stimulation of specific microbial communities via the exudation of sugars, organic acids, and plant secondary metabolites that are used as substrates for microbial growth. Plant roots as well as associated microorganisms may also facilitate the mobilization and biodegradability of organic pollutants via the production and release of rhamnolipids and other biosurfactants. The stimulation of co-metabolic degradation of organic pollutants by enzymes that are released by plants or the rhizosphere microbial community is considered another important pathway of rhizodegradation. Other stimulation effects may include signalling and cooperative interactions of rhizosphere consortia.
Currently, there are only a few practical applications of such rhizotechnology. A main limitation is the lack of detailed understanding of the processes that are involved, making plant microbe–based remedial actions hardly predictable. More fundamental research elucidating the complexity and key control points of rhizodegradation is therefore urgently required. Some presentations provided examples of detailed investigations of rhizosphere effects such as that of root exudation on PAH or organopesticide degradation or the role of microbial community structure and mycorrhizal associations on rhizodegradation of PAH. However, most of the work required is ahead of us. Novel tools such as microsite sampling combined with molecular probes hold promise for stimulating significant progress in the near future.
Several presentations were dedicated to the fate and management of metals and radionuclides. Some papers addressed the effects of altered chemical milieus in the rhizosphere on metal or radiocesium mobility and/or phytoavailability. Others dealt with the role of mycorrhizal associations on metal uptake in plants and the options of manipulating the mycorrhizosphere in phytoremediation technologies. As already stated for organic pollutants, it is obvious also for inorganic pollutants that, despite all the progress of rhizosphere research during the past century, applications of our knowledge are still limited and substantial further research is needed to make better use of the rhizosphere in pollutant management and control.
We wish to acknowledge the sponsorship of the European Science Foundation through COST Action 631 (Understanding and Modelling Plant-Soil Interactions in the Rhizosphere Environment [UMPIRE]), the Organisation for Economic Co-operation and Development (OECD), and the GSF National Research Center for Environment and Health (Neuherberg, Germany).
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REFERENCES
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- Hartmann, A., M. Schmid, W.W. Wenzel, and P. Hinsinger (ed) 2005. Rhizosphere 2004—Perspectives and Challenges—A Tribute to Lorenz Hiltner. GSF-Bericht 05/05. GSF Natl. Res. Center for Environ. and Health, Neuherberg, Germany.
- Hiltner, L. 1904. Über neuere Erfahrungen und Probleme auf dem Gebiete der Bodenbakteriologie unter besonderer Berücksichtigung der Gründüngung und der Brache. Arb. DLG 98:59–78.
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Introduction
REFERENCES