AUTHOR=Li Qiang , Wu Yawei , Chen Wei , Jin Rong , Kong Fanlei , Ke Yongpei , Shi Haichun , Yuan Jichao 

TITLE=Cultivar Differences in Root Nitrogen Uptake Ability of Maize Hybrids

JOURNAL=Frontiers in Plant Science

VOLUME=8

YEAR=2017

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2017.01060

DOI=10.3389/fpls.2017.01060

ISSN=1664-462X

ABSTRACT=<p>Although, considerable differences in root size in response to nitrogen (N) application among crop species and cultivars have been widely reported, there has been limited focus on the differences in root N uptake ability. In this study, two maize (<italic>Zea mays</italic> L.) hybrids, Zhenghong 311 (ZH 311, N-efficient) and Xianyu 508 (XY 508, N-inefficient), were used to compare differences in root N uptake ability. The two cultivars were grown in field pots Experiment I (Exp. I) and hydroponic cultures Experiment II (Exp. II) supplemented with different concentrations of N fertilizer. In both experiments, the levels of accumulated N were higher in ZH 311 than in XY 508 under low- and high-N supply, and the increment in accumulated N was greater under N deficiency. The maximum N uptake rate (<italic>V</italic><sub>m</sub>) and average N uptake rate (<italic>V</italic><sub>a</sub>) in Exp. I, the root N kinetic parameter maximum uptake rate (<italic>V</italic><sub>max</sub>) per fresh weight (FW) and <italic>V</italic><sub>max</sub> per plant in Exp. II, and the root N uptake rate in both experiments were significantly higher for ZH 311 than for XY 508. In contrast, the root-to-shoot N ratio in both experiments and the root N kinetic parameter Michaelis constant (<italic>K</italic><sub>m</sub>) in in Exp. II were markedly higher in XY 508 than in ZH 311, particularly under N-deficient conditions. Higher root N kinetic parameters <italic>V</italic><sub>max</sub> per FW and <italic>V</italic><sub>max</sub> per plant and lower <italic>K</italic><sub>m</sub> values contributed to higher N affinity and uptake potential, more coordinated N distribution in the root and shoot, and higher root N uptake rates throughout the growth stages, thus enhancing the N accumulation and yield of the N-efficient maize cultivar. We conclude that the N uptake ability of roots in the N-efficient cultivar ZH 311 is significantly greater than that in the N-inefficient cultivar XY 508, and that this advantage is more pronounced under N-deficient conditions. The efficient N acquisition in ZH 311 is due to higher N uptake rate per root FW under optimal N conditions and the comprehensive effects of root size and N uptake rate per root FW under N deficiency.</p>