Transpiration, and Nitrogen Uptake and Flow in Two Maize (Zea mays L.) Inbred Lines as Affected by Nitrogen Supply

BACKGROUND AND AIMS: 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.KEY 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 NO3^–1 reduction towards the roots. The major nitrogenous compound in the xylem sap was NO3^–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.