Transpiration, and nitrogen uptake and flow in two maize (Zea mays L.) inbred lines as affected by nitrogen supply.
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.
Niu
Junfang
J
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.
Chen
Fanjun
F
Mi
Guohua
G
Li
Chunjian
C
Zhang
Fusuo
F
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*
D014867:Water; D009584:Nitrogen