Inland Waters, Vol 6, No 3 (2016)

Absence of phosphorus at iron coatings on Elodea nuttallii roots point toward a redox mediated phosphorus uptake strategy; Implications for a root-microbe relationship.

Susanne Halbedel (née Angelstein)
Pages: 343-351


In Europe and Asia, Elodea nuttallii is known as an invasive alien species that causes serious economic and environmental problems. This study demonstrated Elodea’s ability to affect the biogeochemical character of its rhizosphere by investigating the radial oxygen loss (ROL) of Elodea’s roots and its influence on the spatial variability of root precipitate formation as well as microbial colonization. The oxygen content on the root surface was measured using a Clark-type microelectrode, oxic and anoxic microzone patterns were visualized by means of methylene blue colorization, and the spatial distribution of root-associated microorganisms was examined using a confocal laser scanning microscope. The elemental composition of the root plaque was also analysed using a scanning electron microscope equipped with an X-ray microanalysis tool. Oxic and anoxic microzone patterns were found along the root surfaces of E. nuttallii; the iron deposits were spatially inhomogeneous and corresponded with root associated microbes. The absence of phosphorus at iron coatings was unexpected and raised questions regarding a redox-mediated phosphorus uptake strategy based on a root–microbe relationship. A decrease in the number of visible microbes with increasing iron plaque formation was also observed; thus, the spatial mosaic of microbial root colonization seems to be linked to ROL and iron plaque formation. These findings will generate studies on aquatic plant-associated microbes and their role in nutrient uptake of aquatic plants, especially on how such an overwhelming phosphorus uptake strategy could jeopardize phosphorus and weed management activities.
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