The influence of enriched rhizosphere CO2 on N uptake and metabolism in wild-type and NR-deficient barley plants

M. D. Cramer, N. A. Savidov, S. H. Lips

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    30 Scopus citations


    Positive influences of high concentrations of dissolved inorganic carbon (DIC) in the growth medium of salinity-stressed plants are associated with carbon assimilation through phosphoenolpyruvate carboxylase (PEPc) activity in roots; and also in salinity-stressed tomato plants, enriched CO2 in the rhizosphere increases NO3- uptake. In the present study, wild-type and nitrate reductase-deficient plants of barley (Hordeum vulgare L. cv. Steptoe) were used to determine whether the influence of enriched CO2 on NO3-uptake and metabolism is dependent on the activity of nitrate reductase (NR) in the plant. Plants grown in NH4+ and aerated with ambient air, were transferred to either NO3-or NH4+ solutions and aerated with air containing between 0 and 6 500 μmol mol-1 CO2. Nitrogen uptake and tissue concentrations of NO3- and NH4+ were measured as well as activities of NR and PEPc. The uptake of NO3- by the wild-type was increased by increasing CO2. This was associated with increased in vitro NR activity, but increased uptake of NO3- was found also in the NR-deficient genotype when exposed to high CO2 concentrations; so that the influence of CO2 on NO3- uptake was independent of the reduction of NO3- and assimilation into amino acids. The increase in uptake of NO3- in wild-type plants with enriched CO2 was the same at pH 7 as at pH 5, indicating that the relative abundance of HCO3- or CO2 in the medium did not influence NO3- uptake. Uptake of NH4+ was decreased by enriched CO2 in a pH (5 or 7) independent fashion. Thus NO3- and NH4+ uptakes are influenced by the CO2 component of DIC independently of anaplerotic carbon provision for amino acid synthesis, and CO2 may directly affect the uptake of NO3- and NH4+ in ways unrelated to the NR activity in the tissue.

    Original languageEnglish
    Pages (from-to)47-54
    Number of pages8
    JournalPhysiologia Plantarum
    Issue number1
    StatePublished - 1 Jan 1996


    • Barley
    • Carbon dioxide
    • Hordeum vulgare
    • Nitrate
    • Nitrate reductase
    • Phosphoenolpyruvate carboxylase
    • Respiration

    ASJC Scopus subject areas

    • Physiology
    • Genetics
    • Plant Science
    • Cell Biology


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