title: The influence of root assimilated inorganic carbon on nitrogen acquisition/assimilation and carbon partitioning.
abstract: Understanding of the influences of root-zone CO2 concentration on nitrogen (N) metabolism is limited. The influences of root-zone CO2 concentration on growth, N uptake, N metabolism and the partitioning of root assimilated 14C were determined in tomato (Lycopersicon esculentum). Root, but not leaf, nitrate reductase activity was increased in plants supplied with increased root-zone CO2. Root phosphoenolpyruvate carboxylase activity was lower with NO3(-)- than with NH4(+)-nutrition, and in the latter, was also suppressed by increased root-zone CO2. Increased growth rate in NO3(-)-fed plants with elevated root-zone CO2 concentrations was associated with transfer of root-derived organic acids to the shoot and conversion to carbohydrates. With NH4(+)-fed plants, growth and total N were not altered by elevated root-zone CO2 concentrations, although 14C partitioning to amino acid synthesis was increased. Effects of root-zone CO2 concentration on N uptake and metabolism over longer periods (> 1 d) were probably limited by feedback inhibition. Root-derived organic acids contributed to the carbon budget of the leaves through decarboxylation of the organic acids and photosynthetic refixation of released CO2.
authors.affiliation: Department of Botany, University of Stellenbosch, Private Bag XI, Matieland 7602, South Africa.
authors.forename: A
authors.initials: A
authors.lastname: Viktor
authors.forename: M D
authors.initials: MD
authors.lastname: Cramer
mesh_terms: D001692:Biological Transport; D002244:Carbon / Q000378:metabolism*; D002245:Carbon Dioxide / Q000378:metabolism* / Q000494:pharmacology; D002256:Carbonic Anhydrases / Q000378:metabolism; D018551:Solanum lycopersicum / Q000254:growth & development / Q000378:metabolism*; D050901:Nitrate Reductase; D009565:Nitrate Reductases / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism*; D010730:Phosphoenolpyruvate Carboxylase / Q000378:metabolism; D018515:Plant Leaves / Q000378:metabolism; D018517:Plant Roots / Q000378:metabolism*; D018547:Plant Stems / Q000378:metabolism; D012987:Soil / Q000032:analysis; D013997:Time Factors
chemical_list: D012987:Soil; D002245:Carbon Dioxide; D002244:Carbon; D009565:Nitrate Reductases; D050901:Nitrate Reductase; D010730:Phosphoenolpyruvate Carboxylase; D002256:Carbonic Anhydrases; D009584:Nitrogen