Journal
FIELD CROPS RESEARCH
Volume 115, Issue 1, Pages 85-93Publisher
ELSEVIER
DOI: 10.1016/j.fcr.2009.10.006
Keywords
Nitrogen uptake; Root growth; Root spatial distribution; Shoot growth potential; Zea mays
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Funding
- Natural Science Foundation of Hebei Province [C2007000525]
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Variation in nitrogen (N) acquisition ability is known to exist among maize genotypes. Field experiments were conducted and the N-efficient maize inbred line 478 and the N-inefficient line Wu312 were employed to illustrate whether the amount of N taken up in maize plants with different N acquisition ability was determined by the shoot growth potential or by the root size. To meet the accelerated growth of the shoot from the jointing stage to the grain-filling stage, the net N gain in whole plants of both genotypes increased dramatically and accounted for 77% and 74% of the total N increment in 478 and Wu312, respectively. Similarly, the 4th to 8th nodal root whorls were initiated predominantly between 35 and 76 d after sowing, which accounted for about 90% of the total root length on 93 d after sowing. The whole plant N content of the N-efficient 478 was significantly higher than that of the N-inefficient Wu312. 478 had also longer root length, including axial and lateral roots, of the embryonic roots and each whorl of shoot-borne roots, and greater root length density (RLD) than Wu312. In spite of the smaller root size, Wu312 had higher shoot N concentration than 478 during the whole growth period, implying that N was not limited for shoot growth in Wu312. It was concluded that maize root growth, especially initiation and development of the shoot-borne roots, as well as the amount of N taken up were coordinated with shoot growth and demand for nutrients. Although a large root system and high RLD in the soil profile were beneficial for efficient N acquisition, amount of N taken up by the two maize genotypes in the presence of sufficient N supply was determined by the shoot growth potential, and not by the root size. (C) 2009 Elsevier B.V. All rights reserved.
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