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CO2 and O2 dynamics in leaves of aquatic plants with C3 or CAM photosynthesis - application of a novel CO2 microsensor

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  • Ole Pedersen, Københavns Universitet, University of Western Australia
  • ,
  • Timothy D. Colmer, University of Western Australia
  • ,
  • Emilio Garcia-Robledo, Univ Cadiz, Universidad de Cadiz, Dept Biol, Ecol
  • ,
  • Niels P. Revsbech

Background and Aims Leaf tissue CO2 partial pressure (pCO(2)) shows contrasting dynamics over a diurnal cycle in C-3 and Crassulacean Acid Metabolism (CAM) plants. However, simultaneous and continuous monitoring of pCO(2) and pO(2) in C-3 and CAM plants under the same conditions was lacking. Our aim was to use a new CO2 microsensor and an existing O-2 microsensor for non-destructive measurements of leaf pCO(2) and pO(2) dynamics to compare a C-3 and a CAM plant in an aquatic environment.

Methods A new amperometric CO2 microsensor and an O-2 microsensor elucidated with high temporal resolution the dynamics in leaf pCO(2) and pO(2) during light-dark cycles for C-3 Lobelia dortmanna and CAM Littorella uniflora aquatic plants. Underwater photosynthesis, dark respiration, tissue malate concentrations and sediment CO2 and O-2 were also measured.

Key Results During the dark period, for the C-3 plant, pCO(2) increased to approx. 3.5 kPa, whereas for the CAM plant CO2 was mostly below 0.05 kPa owing to CO2 sequestration into malate. Upon darkness, the CAM plant had an initial peak in pCO(2) (approx. 0.16 kPa) which then declined to a quasi-steady state for several hours and then pCO(2) increased towards the end of the dark period. The C-3 plant became severely hypoxic late in the dark period, whereas the CAM plant with greater cuticle permeability did not. Upon illumination, leaf pCO(2) declined and pO(2) increased, although aspects of these dynamics also differed between the two plants.

Conclusions The continuous measurements of pCO(2) and pO(2) highlighted the contrasting tissue gas compositions in submerged C-3 and CAM plants. The CAM leaf pCO(2) dynamics indicate an initial lag in CO(2 )sequestration to malate, which after several hours of malate synthesis then slows. Like the use of O-2 microsensors to resolve questions related to plant aeration, deployment of the new CO2 microsensor will benefit plant ecophysiology research.

TidsskriftAnnals of Botany
Sider (fra-til)605-615
Antal sider11
StatusUdgivet - 14 sep. 2018

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