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O2 dynamics in the rhizosphere of young rice plants (Oryza sativa L.) as studied by planar optodes.

Larsen M, Santner J, Oburger E, Wenzel WW, Glud RN - Plant Soil (2015)

Bottom Line: At onset of darkness, oxia in the rhizosphere was drastically reduced, but subsequently oxia gradually increased, presumably as root and/or soil respiration declined.The study demonstrates a high spatio-temporal heterogeneity in rhizosphere O2 dynamics and difference in ROL between different parts of the rhizosphere.The work documents that spatio-temporal measurements are important to fully understand and account for the highly variable O2 dynamics and associated biogeochemical processes and pathways in the rice rhizosphere.

View Article: PubMed Central - PubMed

Affiliation: Institute of Biology and Nordic Center for Earth Evolution (NordCEE), University of Southern Denmark, 5320 Odense M, Denmark ; Scottish Marine Institute, Scottish Association for Marine Science, Oban, Scotland PA37 1QA UK ; Greenland Climate Research Centre (CO Greenland Institute of National resources), Kivioq 2, Box 570, 3900 Nuuk, Greenland.

ABSTRACT

Background and aims: Radial O2 loss (ROL) strongly affect the O2 availability in the rhizosphere of rice. The ROL create an oxic zone around the roots, protecting the plant from toxic reduced chemical species and regulates the redox chemistry in the soil. This study investigates the spatio-temporal variability in O2 dynamics in the rice rhizosphere.

Method: Applying high-resolution planar optode imaging, we investigated the O2 dynamics of plants grown in water saturated soil, as a function of ambient O2 level, irradiance and plant development, for submerged and emerged plants.

Results: O2 leakage was heterogeneously distributed with zones of intense leakage around roots tips and young developing roots. While the majority of roots exhibited high ROL others remained surrounded by anoxic soil. ROL was affected by ambient O2 levels around the plant, as well as irradiance, indicating a direct influence of photosynthetic activity on ROL. At onset of darkness, oxia in the rhizosphere was drastically reduced, but subsequently oxia gradually increased, presumably as root and/or soil respiration declined.

Conclusion: The study demonstrates a high spatio-temporal heterogeneity in rhizosphere O2 dynamics and difference in ROL between different parts of the rhizosphere. The work documents that spatio-temporal measurements are important to fully understand and account for the highly variable O2 dynamics and associated biogeochemical processes and pathways in the rice rhizosphere.

No MeSH data available.


Related in: MedlinePlus

Volume specific O2 respiration at a typical root tip. Rates are estimated based on extracted concentration profiles across the tip. The rates are calculated based on simple planar diffusion geometry. Values are mean for both “sides” of the root tip, with error bars representing ± SD, n = 2. The grey shaded area represents the dark period. The upper and lowers horizontal dashed lines represent the mean O2 respiration for the light and dark period, respectively (Light: 0.081 nmol cm−3 s−1, ±SD = 0.5 × 10−2, n = 6; Dark: 0.064 nmol cm−3 s−1 ± SD = 0.96 × 10−2, n = 10). In comparison, the soil volume specific respiration as calculated for the primary soil-water interface was found to amount to 0.07 nmol cm−3 s−1 ± SD = 0.015, n = 6
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Fig7: Volume specific O2 respiration at a typical root tip. Rates are estimated based on extracted concentration profiles across the tip. The rates are calculated based on simple planar diffusion geometry. Values are mean for both “sides” of the root tip, with error bars representing ± SD, n = 2. The grey shaded area represents the dark period. The upper and lowers horizontal dashed lines represent the mean O2 respiration for the light and dark period, respectively (Light: 0.081 nmol cm−3 s−1, ±SD = 0.5 × 10−2, n = 6; Dark: 0.064 nmol cm−3 s−1 ± SD = 0.96 × 10−2, n = 10). In comparison, the soil volume specific respiration as calculated for the primary soil-water interface was found to amount to 0.07 nmol cm−3 s−1 ± SD = 0.015, n = 6

Mentions: We cannot quantitatively discriminate between the importance of the two processes, but we suggest that the resolved dynamic is related to reduced O2 consumption in both the root and the surrounding soil. Both factors are presumably being regulated by the availability of plant derived exudates that in some cases have been demonstrated to decrease during dark periods (Watt and Evans 1999; Badri et al. 2010). The reduction in soil/root respiration, estimated from extracted O2 profiles, during a day-night transition amounted to 32 %, from 0.081 nmol cm−3 s−1 (±SD = 0.5 × 10−2, n = 6) to 0.064 nmol cm−3 s−1 (±SD = 0.96 × 10−2, n = 12) (Fig. 7).Fig. 7


O2 dynamics in the rhizosphere of young rice plants (Oryza sativa L.) as studied by planar optodes.

Larsen M, Santner J, Oburger E, Wenzel WW, Glud RN - Plant Soil (2015)

Volume specific O2 respiration at a typical root tip. Rates are estimated based on extracted concentration profiles across the tip. The rates are calculated based on simple planar diffusion geometry. Values are mean for both “sides” of the root tip, with error bars representing ± SD, n = 2. The grey shaded area represents the dark period. The upper and lowers horizontal dashed lines represent the mean O2 respiration for the light and dark period, respectively (Light: 0.081 nmol cm−3 s−1, ±SD = 0.5 × 10−2, n = 6; Dark: 0.064 nmol cm−3 s−1 ± SD = 0.96 × 10−2, n = 10). In comparison, the soil volume specific respiration as calculated for the primary soil-water interface was found to amount to 0.07 nmol cm−3 s−1 ± SD = 0.015, n = 6
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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Fig7: Volume specific O2 respiration at a typical root tip. Rates are estimated based on extracted concentration profiles across the tip. The rates are calculated based on simple planar diffusion geometry. Values are mean for both “sides” of the root tip, with error bars representing ± SD, n = 2. The grey shaded area represents the dark period. The upper and lowers horizontal dashed lines represent the mean O2 respiration for the light and dark period, respectively (Light: 0.081 nmol cm−3 s−1, ±SD = 0.5 × 10−2, n = 6; Dark: 0.064 nmol cm−3 s−1 ± SD = 0.96 × 10−2, n = 10). In comparison, the soil volume specific respiration as calculated for the primary soil-water interface was found to amount to 0.07 nmol cm−3 s−1 ± SD = 0.015, n = 6
Mentions: We cannot quantitatively discriminate between the importance of the two processes, but we suggest that the resolved dynamic is related to reduced O2 consumption in both the root and the surrounding soil. Both factors are presumably being regulated by the availability of plant derived exudates that in some cases have been demonstrated to decrease during dark periods (Watt and Evans 1999; Badri et al. 2010). The reduction in soil/root respiration, estimated from extracted O2 profiles, during a day-night transition amounted to 32 %, from 0.081 nmol cm−3 s−1 (±SD = 0.5 × 10−2, n = 6) to 0.064 nmol cm−3 s−1 (±SD = 0.96 × 10−2, n = 12) (Fig. 7).Fig. 7

Bottom Line: At onset of darkness, oxia in the rhizosphere was drastically reduced, but subsequently oxia gradually increased, presumably as root and/or soil respiration declined.The study demonstrates a high spatio-temporal heterogeneity in rhizosphere O2 dynamics and difference in ROL between different parts of the rhizosphere.The work documents that spatio-temporal measurements are important to fully understand and account for the highly variable O2 dynamics and associated biogeochemical processes and pathways in the rice rhizosphere.

View Article: PubMed Central - PubMed

Affiliation: Institute of Biology and Nordic Center for Earth Evolution (NordCEE), University of Southern Denmark, 5320 Odense M, Denmark ; Scottish Marine Institute, Scottish Association for Marine Science, Oban, Scotland PA37 1QA UK ; Greenland Climate Research Centre (CO Greenland Institute of National resources), Kivioq 2, Box 570, 3900 Nuuk, Greenland.

ABSTRACT

Background and aims: Radial O2 loss (ROL) strongly affect the O2 availability in the rhizosphere of rice. The ROL create an oxic zone around the roots, protecting the plant from toxic reduced chemical species and regulates the redox chemistry in the soil. This study investigates the spatio-temporal variability in O2 dynamics in the rice rhizosphere.

Method: Applying high-resolution planar optode imaging, we investigated the O2 dynamics of plants grown in water saturated soil, as a function of ambient O2 level, irradiance and plant development, for submerged and emerged plants.

Results: O2 leakage was heterogeneously distributed with zones of intense leakage around roots tips and young developing roots. While the majority of roots exhibited high ROL others remained surrounded by anoxic soil. ROL was affected by ambient O2 levels around the plant, as well as irradiance, indicating a direct influence of photosynthetic activity on ROL. At onset of darkness, oxia in the rhizosphere was drastically reduced, but subsequently oxia gradually increased, presumably as root and/or soil respiration declined.

Conclusion: The study demonstrates a high spatio-temporal heterogeneity in rhizosphere O2 dynamics and difference in ROL between different parts of the rhizosphere. The work documents that spatio-temporal measurements are important to fully understand and account for the highly variable O2 dynamics and associated biogeochemical processes and pathways in the rice rhizosphere.

No MeSH data available.


Related in: MedlinePlus