title: Transpiration, and nitrogen uptake and flow in two maize (Zea mays L.) inbred lines as affected by nitrogen supply.
abstract: OBJECTIVE
  The influence of two nitrogen (N) levels on growth, water relations, and N uptake and flow was investigated in two different inbred lines of maize (N-efficient Zi330 and N-inefficient Chen94-11) to analyse the differences in N uptake and cycling within a plant.
  
  
  METHODS
  Xylem sap from different leaves of the inbred lines cultured in quartz sand was collected by application of pressure to the root system. Plant transpiration was measured on a daily basis by weighing five pots of each of the treatments.
  
  
  RESULTS
  N-efficient Zi330 had a higher relative growth rate and water-use efficiency at both high (4 mm) and low (0.08 mm) N levels. At a high N level, the amount of N taken up was similar for the two inbred lines; the amount of N transported in the xylem and retranslocated in the phloem was slight greater in Chen94-11 than in Zi330. At a low N level, however, the total amount of N taken up, transported in the xylem and retranslocated in the phloem of Zi330 was 2.2, 2.7 and 2.7 times more, respectively, than that of Chen94-11. Independent of inbred line and N level, the amounts of N transported in the xylem and cycled in the phloem were far more than that taken up by roots at the same time. Low N supply shifted NO(3)(-1) reduction towards the roots. The major nitrogenous compound in the xylem sap was NO(3)(-1), when plants grew at the high N level, while amino acid-N was predominant when plants grew at the low N level.
  
  
  CONCLUSIONS
  The N-efficient maize inbred line Zi330 had a higher ability to take up N and cycle N within the plant than N-inefficient Chen94-11 when grown under N-deficiency.
authors.affiliation: The Key Laboratory of Plant Nutrition and Nutrient Cycling, MOA, Key Laboratory of Plant-Soil Interactions, MOE, Department of Plant Nutrition, China Agricultural University, Beijing 100094, China.
authors.forename: Junfang
authors.initials: J
authors.lastname: Niu
authors.forename: Fanjun
authors.initials: F
authors.lastname: Chen
authors.forename: Guohua
authors.initials: G
authors.lastname: Mi
authors.forename: Chunjian
authors.initials: C
authors.lastname: Li
authors.forename: Fusuo
authors.initials: F
authors.lastname: Zhang
mesh_terms: D009584:Nitrogen / Q000378:metabolism*; D018526:Plant Transpiration / Q000502:physiology*; D014867:Water / Q000378:metabolism; D052584:Xylem / Q000378:metabolism; D003313:Zea mays / Q000254:growth & development / Q000378:metabolism / Q000502:physiology*
chemical_list: D014867:Water; D009584:Nitrogen