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Root O2 consumption, CO2 production and tissue concentration profiles in chickpea, as influenced by environmental hypoxia

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DOI

  • Timothy David Colmer, University of Western Australia
  • ,
  • Anders Winkel, Freshwater Biological Laboratory
  • ,
  • Lukasz Kotula, University of Western Australia
  • ,
  • William Armstrong, University of Western Australia, University of Hull
  • ,
  • Niels Peter Revsbech
  • Ole Pedersen, University of Western Australia, University of Copenhagen

Roots in flooded soils experience hypoxia, with the least O2 in the vascular cylinder. Gradients in CO2 across roots had not previously been measured. The respiratory quotient (RQ; CO2 produced : O2 consumed) is expected to increase as O2 availability declines. A new CO2 microsensor and an O2 microsensor were used to measure profiles across roots of chickpea seedlings in aerated or hypoxic conditions. Simultaneous, nondestructive flux measurements of O2 consumption, CO2 production, and thus RQ, were taken for roots with declining O2. Radial profiling revealed severe hypoxia and c. 0.8 kPa CO2 within the root vascular cylinder. The distance penetrated by O2 into the roots was shorter at lower O2. The gradient in CO2 was in the opposite direction to that of O2, across the roots and diffusive boundary layer. RQ increased as external O2 was lowered. For chickpea roots in solution at air equilibrium, O2 was very low and CO2 was elevated within the vascular cylinder; the extent of the severely hypoxic core increased as external O2 was reduced. The increased RQ in roots in response to declining external O2 highlighted the shift from respiration to ethanolic fermentation as the severely hypoxic/anoxic core became a progressively greater proportion of the root tissues.

Original languageEnglish
JournalNew Phytologist
Volume226
Issue2
Pages (from-to)373-384
Number of pages12
ISSN0028-646X
DOIs
Publication statusPublished - 2020

    Research areas

  • anoxic core, Cicer arietinum, diffusive boundary layer, fermentation, microsensors, respiration, respiratory quotient (RQ), stele/vascular cylinder hypoxia

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