The dynamics of oxygen concentration, pH value, and organic acids in the rhizosphere of Juncus spp.

Bloßfeld, Stephan; Gansert, Dirk; Thiele, Björn; Kuhn, Arnd J.; Lösch, R.

doi:10.1016/j.soilbio.2011.02.007

Cited by 140 publications

(89 citation statements)

References 55 publications

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“…Oxygen concentrations in the rhizosphere showed diurnal variations, with peaks of oxygen at 10 a.m. (around 0.4 mg/liter) and low points at midnight (0.1 mg/liter). DOC concentrations in the pore water were essentially constant around 3.8 Ϯ 0.7 mg/liter and revealed that other carbon sources, such as root exudates and derivates thereof, were available to the rhizospheric microbial community (11,16). Although we did not assess the composition of the root exudates in day and night samples, it can be assumed that these showed diurnal patterns comparable to the fluctuating oxygen concentrations (17).…”

Section: Resultsmentioning

confidence: 92%

“…The release of oxygen and organic carbon by any plant root depends on photosynthesis and therefore may exhibit diurnal oscillations (14,15). These oscillations were indeed described for root exudation by Juncus effusus, a common wetland plant (16,17). Fluctuating redox conditions in the rhizosphere of CWs, cooccurring with the day-night regimen (18), as well as the influence of these diurnal fluctuations on various redox transformation processes involving nitrogen compounds (19) and iron (20) have been reported.…”

Section: Importancementioning

confidence: 91%

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Aerobic Toluene Degraders in the Rhizosphere of a Constructed Wetland Model Show Diurnal Polyhydroxyalkanoate Metabolism

Lünsmann

Kappelmeyer

Taubert

et al. 2016

Appl Environ Microbiol

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Constructed wetlands (CWs) are successfully applied for the treatment of waters contaminated with aromatic compounds. In these systems, plants provide oxygen and root exudates to the rhizosphere and thereby stimulate microbial degradation processes. Root exudation of oxygen and organic compounds depends on photosynthetic activity and thus may show day-night fluctuations. While diurnal changes in CW effluent composition have been observed, information on respective fluctuations of bacterial activity are scarce. We investigated microbial processes in a CW model system treating toluene-contaminated water which showed diurnal oscillations of oxygen concentrations using metaproteomics. Quantitative real-time PCR was applied to assess diurnal expression patterns of genes involved in aerobic and anaerobic toluene degradation. We observed stable aerobic toluene turnover by Burkholderiales during the day and night. Polyhydroxyalkanoate synthesis was upregulated in these bacteria during the day, suggesting that they additionally feed on organic root exudates while reutilizing the stored carbon compounds during the night via the glyoxylate cycle. Although mRNA copies encoding the anaerobic enzyme benzylsuccinate synthase (bssA) were relatively abundant and increased slightly at night, the corresponding protein could not be detected in the CW model system. Our study provides insights into diurnal patterns of microbial processes occurring in the rhizosphere of an aquatic ecosystem. IMPORTANCEConstructed wetlands are a well-established and cost-efficient option for the bioremediation of contaminated waters. While it is commonly accepted knowledge that the function of CWs is determined by the interplay of plants and microorganisms, the detailed molecular processes are considered a black box. Here, we used a well-characterized CW model system treating toluenecontaminated water to investigate the microbial processes influenced by diurnal plant root exudation. Our results indicated stable aerobic toluene degradation by members of the Burkholderiales during the day and night. Polyhydroxyalkanoate synthesis in these bacteria was higher during the day, suggesting that they additionally fed on organic root exudates and reutilized the stored carbon compounds during the night. Our study illuminates microbial processes occurring in the rhizosphere of an aquatic ecosystem. C onstructed wetlands (CWs) are well-established treatment systems for the bioremediation of contaminated waters (1), including industrial effluents originating from petroleum refineries and their associated contaminated sites (2, 3). Aromatic hydrocarbons present in those wastewaters can effectively be removed in CWs (4-7), largely driven by the interplay of plant physiology and microbial degradation processes in the rhizosphere (8, 9). As in any planted habitat, the rhizosphere of CWs is a complex environment with increased abundance and activity of microorganisms compared to those in the surrounding zones (10). It is shaped by the roots and plant-derived exu...

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Section: Resultsmentioning

confidence: 92%

Section: Importancementioning

confidence: 91%

Aerobic Toluene Degraders in the Rhizosphere of a Constructed Wetland Model Show Diurnal Polyhydroxyalkanoate Metabolism

Lünsmann

Kappelmeyer

Taubert

et al. 2016

Appl Environ Microbiol

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“…As a result, substrate limitation in the rhizosphere may have reduced the rate of soil respiration. In addition, the enhancement of convective flows in PAR can have a considerable influence on root radial oxygen loss in Phragmites australis Armstrong, 1988, 1990), which plays an important role in the physicochemical environment of the rhizosphere, particularly for wetland plants growing in oxygen deficient waterlogged soils (Blossfeld et al, 2011). As a consequence, the difference in root radial oxygen loss between sunny and cloudy days can lead to the changes in rhizosphere biogeochemistry (e.g.…”

Section: Gpp Regulates Diurnal Soil Respiration On An Ecosystem Scalementioning

confidence: 99%

“…As a consequence, the difference in root radial oxygen loss between sunny and cloudy days can lead to the changes in rhizosphere biogeochemistry (e.g. Blossfeld et al, 2011), resulting in changes in rhizosphere respiration.…”

Section: Gpp Regulates Diurnal Soil Respiration On An Ecosystem Scalementioning

confidence: 99%

Ecosystem photosynthesis regulates soil respiration on a diurnal scale with a short-term time lag in a coastal wetland

Han

Luo

et al. 2014

Soil Biology and Biochemistry

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a b s t r a c tAlthough increasing evidence has provided that soil respiration is strongly related to recent canopy photosynthesis, doubts remain as to the extent to which primary productivity controls soil respiratory and the speed of the link between soil respiration and photosynthesis. Based on the automated measurements of soil respiration and eddy covariance measurements of ecosystem photosynthesis (i.e. gross primary production, GPP) in a coastal wetland, we assessed the speed of link between ecosystem photosynthesis and soil respiration on the diurnal scale, and quantified the control of the ecosystem primary production on diurnal soil respiration. On the diurnal scale, the time of daily peak soil respiration lagged GPP but preceded soil temperature on both sunny and cloudy days. Daytime soil respiration was significantly linearly correlated with GPP with a lag of 1.5 h on sunny days and 1 h on cloudy days, respectively. By taking advantage of the natural shift of sunny and cloudy days without disturbance to the plant-soil system, our results also indicated that the changes in soil temperature and GPP together explained 53% of the changes in daytime soil respiration rates between sunny days and adjacent cloudy days. Under the same soil temperature, changes in soil respiration rates were strongly correlated with changes in GPP between sunny days and adjacent cloudy days. We therefore conclude that recent canopy photosynthesis regulates soil respiration on a diurnal scale with a short-term time lag. Thus, it is necessary to take into account the influence of photosynthesis on soil respiration in order to accurately simulate the magnitude and variation of soil respiration, especially at short and medium temporal scales.

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“…Even so, its use in wetlands and shallow waters is still limited to very few species including Juncus spp. (Blossfeld et al 2011), Zostera marina (Frederiksen and Glud 2006;Jensen et al 2005) and Carex appressa (Minett et al 2013). In this study, planar optodes were used to investigate plant-mediated sediment oxygenation around the roots of the intertidal marsh grass S. anglica, visualizing the presence of oxic root zones at depth in the sediment.…”

Section: Introductionmentioning

confidence: 99%

The Dynamics of Plant-Mediated Sediment Oxygenation in Spartina anglica Rhizospheres—a Planar Optode Study

Koop-Jakobsen

Wenzhöfer

2014

Estuaries and Coasts

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Belowground sediment oxygenation in rhizospheres of wetland plants promotes nutrient uptake, serve as protection against toxic reduced compounds and play an important role in wetland nutrient cycling. The presence of 1.5-mm-wide oxic zones around roots of the intertidal marsh grass Spartina anglica was demonstrated below the sediment surface using planar optode technology recording 2D images of the sediment oxygen distribution. Oxic root zones were restricted to the root tips stretching up to 16 mm along the roots with an oxygen concentration up to 85 μmol L −1 detected at the root surface. Radial oxygen loss across the root surface ranged from 250 to 300 nmol m −2 s −1 , which is comparable to other wetland plants. During air exposure of the aboveground biomass, atmospheric oxygen was the primary source for belowground oxygen transport, and light availability only had a minor effect on the belowground sediment oxygenation. During inundations completely submerging the aboveground biomass cutting off access to atmospheric oxygen, oxic root zones diminished significantly in the light and were completely eliminated in darkness. Within the time frame of a normal tidal inundation (~1.5 h), photosynthetic oxygen production maintained the presence of oxic root zones in light, whereas oxic root zones were eliminated within 1 h in darkness. The results show that the sediment oxygenation in Spartina anglica rhizospheres is temporally dynamic as well as spatially variable along the roots.

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The dynamics of oxygen concentration, pH value, and organic acids in the rhizosphere of Juncus spp.

Cited by 140 publications

References 55 publications

Aerobic Toluene Degraders in the Rhizosphere of a Constructed Wetland Model Show Diurnal Polyhydroxyalkanoate Metabolism

Aerobic Toluene Degraders in the Rhizosphere of a Constructed Wetland Model Show Diurnal Polyhydroxyalkanoate Metabolism

Ecosystem photosynthesis regulates soil respiration on a diurnal scale with a short-term time lag in a coastal wetland

The Dynamics of Plant-Mediated Sediment Oxygenation in Spartina anglica Rhizospheres—a Planar Optode Study

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