Rhizospheric exudation of Eriophorum vaginatum L. — Potential link to methanogenesis |
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Authors: | S Saarnio L Wittenmayer W Merbach |
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Institution: | 1. Biologian laitos, Joensuun yliopisto, PL 111, FIN-80101, Joensuu, Finland 2. Institut für Bodenkunde und Pflanzenern?hrung, Professur Physiologie und Ern?hrung der Pflanzen, Martin-Luther-Universit?t Halle-Wittenberg, Adam-Kuckhoff-Stra?e 17b, D-06108, Halle (Saale), Germany
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Abstract: | Root exudates are a direct link between primary production in higher plants and methanogenesis. The relationship has been
widely studied on rice paddies, but less is known about its role in wetlands populated by naturally occurring species. This
study provides information about the amount and composition of root exudates produced by a widespread mire plant, Eriophorum vaginatum L. For this purpose, E. vaginatum plants were grown in quartz sand in pots from April to October, and root exudates were collected once a month by percolation
of the cultivation substrate. In June and October, a set of plants was labelled with 14CO2 for two days and subsequently harvested for the determination of dry weight and for root exudates collected by the dipping
method. The study supports earlier findings that natural wetland plants can enhance methanogenesis in their rhizosphere via
active and seasonally varying exudation, but that the amount of exuded carbon (C) is many times lower than that delivered
via litter formation. At both harvests in June and October, the proportion of incorporated radioactivity in shoots, roots
and exudates was 92–96%, 4–8%, and 0.2%, respectively. New C was primarily fixed in the metabolically important carbohydrates,
as well as acid anions that composed the main compounds of the new exudates. However, microbes seemed to rapidly metabolise
the exudates into other substances like acetate. This was the dominant compound in the rhizoplane and rhizosphere, and it
was the only detected substance that occurred in higher amounts outside the roots than inside them. Further studies in the
field, including the quantification of gaseous end products, are necessary to complete our understanding of the carbon cycling
in E. vaginatum-soil-microbe-system. |
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Keywords: | 14C labelling carbohydrates carbon allocation Eriophorum vaginatum organic acids |
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