Dynamics of oxygen and carbon dioxide in rhizospheres of Lobelia dortmanna – a planar optode study of belowground gas exchange between plants and sediment

Abstract

Root-mediated CO uptake, O release and their effects on O and CO dynamics in the rhizosphere of Lobelia dortmanna were investigated. Novel planar optode technology, imaging CO and O distribution around single roots, provided insights into the spatiotemporal patterns of gas exchange between roots, sediment and microbial community. In light, O release and CO uptake were pronounced, resulting in a distinct oxygenated zone (radius: c. 3 mm) and a CO -depleted zone (radius: c. 2 mm) around roots. Simultaneously, however, microbial CO production was stimulated within a larger zone around the roots (radius: c. 10 mm). This gave rise to a distinct pattern with a CO minimum at the root surface and a CO maximum c. 2 mm away from the root. In darkness, CO uptake ceased, and the CO -depleted zone disappeared within 2 h. By contrast, the oxygenated root zone remained even after 8 h, but diminished markedly over time. A tight coupling between photosynthetic processes and the spatiotemporal dynamics of O and CO in the rhizosphere of Lobelia was demonstrated, and we suggest that O -induced stimulation of the microbial community in the sediment increases the supply of inorganic carbon for photosynthesis by building up a CO reservoir in the rhizosphere.

Plant-Sediment Interactions in Salt Marshes – An Optode Imaging Study of O2, pH, and CO2 Gradients in the Rhizosphere

“…Planar optode studies on CO 2 dynamics in rhizospheres have not yet been applied on wetland plants, and only two studies have used planar optodes for rhizosphere CO 2 investigations. Blossfeld et al (2013) and Lenzewski et al (2018) demonstrated increased CO 2 concentrations around individual roots originating from both root and microbial respiration in the legume Viminaria juncea and in the freshwater plant Lobelia dortmanna , respectively, showing that growing roots exhibit a large zone of influence on sediment CO 2 content more than 1 cm away from the root surface.…”

“…Understanding the dynamics of O 2 , pH, and CO 2 in rhizospheres is crucial for understanding important ecosystem functions, as these parameters are key drivers of biogeochemical processes involved in carbon and nutrient cycling ( Hinsinger et al, 2009 ). In vegetated waterlogged sediments, steep gradients of O 2 , pH, and CO 2 build up around roots, demonstrating a particularly pronounced plant control over these parameters ( Blossfeld et al, 2013 ; Koop-Jakobsen et al, 2017 ; Lenzewski et al, 2018 ). Plant-mediated sediment oxygenation and rhizosphere acidification are key mechanisms by which wetland plants improve nutrient availability and uptake ( Bradley and Morris, 1990 ; Lai et al, 2012 ) and weaken the impact of reduced phytotoxins, such as H 2 S, Fe(II), and Mn(II) ( Rozema et al, 1985 ; Lee, 1999 ; Pezeshki, 2001 ).…”

The rhizosphere of aquatic plants is a habitat for cable bacteria

“…Moreover, aquatic plants can release oxygen into the rhizosphere—the zone surrounding the roots—producing geochemical gradients that are subject to daily fluctuations as photosynthesis ceases during night and the oxygenated zone diminishes (Lenzewski et al . 2018). In the oxygenated zone, abiotic and biotic sulfide oxidation play an essential role in protecting the roots against phytotoxic sulfide (Sand-Jensen, Prahl and Stokholm 1982; Jensen, Kühl and Priemé 2007; Lamers et al .…”

High Resolution Assessment of Spatio-Temporal Changes in O2 Concentration in Root-Pathogen Interaction

“…The measured root respiration rates were of the same order of magnitude as those observed by Dong et al ( 2011 ), in a wetland mesocosm for the aquatic plant Acorus calamus L. (14.4–30.3 g O 2 m −2 d −1 ). The small number of available studies and the lack of experimental details (e.g., area, temperature, pressure) (Hadas and Okon, 1987 ; Tschiersch et al, 2012 ; Han et al, 2016 ; Rudolph-Mohr et al, 2017 ; Lenzewski et al, 2018 ) does not allow additional comparison with in vitro respiration rates. The change in O 2 % air saturation for the fungus alone (Δ = 8.6) was lower than that measured in the fungus during root-fungus interaction (12.6 < Δ < 17.4).…”