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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

a Temporal development of the mean O2 level (black circle) and the oxic area (white circle) in the rhizosphere of a rice plant during a light/dark transition for an emerged plant (see text for explanation). The oxic area was defined as the area with O2 levels >1 % air sat. Light grey color represent the dark period. The O2 levels represent the mean value within the corresponding oxic area and are based on measurements of 60,763 to 76,388 pixels. b Development of the oxic area in the rhizosphere as function of irradiance for an emerged (black bars) and submerged plant (white bars). The difference in oxic area for the two plants is due to variation in plant size. Error bars represent SD, calculated form three individual images at each irradiance level. Each image is based on measurements of 25,294 to 41,502 pixels
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Fig2: a Temporal development of the mean O2 level (black circle) and the oxic area (white circle) in the rhizosphere of a rice plant during a light/dark transition for an emerged plant (see text for explanation). The oxic area was defined as the area with O2 levels >1 % air sat. Light grey color represent the dark period. The O2 levels represent the mean value within the corresponding oxic area and are based on measurements of 60,763 to 76,388 pixels. b Development of the oxic area in the rhizosphere as function of irradiance for an emerged (black bars) and submerged plant (white bars). The difference in oxic area for the two plants is due to variation in plant size. Error bars represent SD, calculated form three individual images at each irradiance level. Each image is based on measurements of 25,294 to 41,502 pixels

Mentions: Light availability affected the O2 level in the rhizosphere for both emerged and submerged plants. For an emerged plant the onset of darkness lead to a rapid decrease in the oxic rhizosphere area of 19.2 % (Fig. 2a) from a stable value of 1080 mm2 in light, to a minimum of 876 mm2 ~ 2 h after the onset of darkness. The decrease in O2 was closely matched by a simultaneous decrease of 24.3 % in the mean O2 level within the oxic area. After the initial decrease the O2 availability increased during the prolonged exposures to darkness (Fig. 2a). During a period of ~8 h the absolute increase in total rhizosphere oxic area and mean O2 level, was found to be 41.8 mm2 and 0.51 % air sat., corresponding to an increase of 4.77 and 4.80 %, respectively. The trend of increasing O2 levels during darkness was observed for several day-night transitions and all plants, but the changes differed for different sections of the rhizospheres. The mean O2 level at the basal root zone and at root tips was observed to increase by 0.17–0.19 % air sat. h−1. In contrast single roots showed only an increase of ~0.04 % air sat. h−1.Fig. 2


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)

a Temporal development of the mean O2 level (black circle) and the oxic area (white circle) in the rhizosphere of a rice plant during a light/dark transition for an emerged plant (see text for explanation). The oxic area was defined as the area with O2 levels >1 % air sat. Light grey color represent the dark period. The O2 levels represent the mean value within the corresponding oxic area and are based on measurements of 60,763 to 76,388 pixels. b Development of the oxic area in the rhizosphere as function of irradiance for an emerged (black bars) and submerged plant (white bars). The difference in oxic area for the two plants is due to variation in plant size. Error bars represent SD, calculated form three individual images at each irradiance level. Each image is based on measurements of 25,294 to 41,502 pixels
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4495287&req=5

Fig2: a Temporal development of the mean O2 level (black circle) and the oxic area (white circle) in the rhizosphere of a rice plant during a light/dark transition for an emerged plant (see text for explanation). The oxic area was defined as the area with O2 levels >1 % air sat. Light grey color represent the dark period. The O2 levels represent the mean value within the corresponding oxic area and are based on measurements of 60,763 to 76,388 pixels. b Development of the oxic area in the rhizosphere as function of irradiance for an emerged (black bars) and submerged plant (white bars). The difference in oxic area for the two plants is due to variation in plant size. Error bars represent SD, calculated form three individual images at each irradiance level. Each image is based on measurements of 25,294 to 41,502 pixels
Mentions: Light availability affected the O2 level in the rhizosphere for both emerged and submerged plants. For an emerged plant the onset of darkness lead to a rapid decrease in the oxic rhizosphere area of 19.2 % (Fig. 2a) from a stable value of 1080 mm2 in light, to a minimum of 876 mm2 ~ 2 h after the onset of darkness. The decrease in O2 was closely matched by a simultaneous decrease of 24.3 % in the mean O2 level within the oxic area. After the initial decrease the O2 availability increased during the prolonged exposures to darkness (Fig. 2a). During a period of ~8 h the absolute increase in total rhizosphere oxic area and mean O2 level, was found to be 41.8 mm2 and 0.51 % air sat., corresponding to an increase of 4.77 and 4.80 %, respectively. The trend of increasing O2 levels during darkness was observed for several day-night transitions and all plants, but the changes differed for different sections of the rhizospheres. The mean O2 level at the basal root zone and at root tips was observed to increase by 0.17–0.19 % air sat. h−1. In contrast single roots showed only an increase of ~0.04 % air sat. h−1.Fig. 2

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