Cultivar Differences in Root Nitrogen Uptake Ability of Maize Hybrids

Area of Science:

• Agricultural Science
• Plant Physiology
• Crop Science

Background:

• Root size variations in response to nitrogen (N) application are well-documented across crop species and cultivars.
• Limited research has focused on the comparative root nitrogen (N) uptake abilities between different crop cultivars.
• Understanding cultivar-specific N uptake is crucial for optimizing N fertilizer use efficiency in maize (Zea mays L.).

Purpose of the Study:

• To compare the root nitrogen (N) uptake abilities of two maize hybrids with differing N efficiencies: Zhenghong 311 (ZH 311, N-efficient) and Xianyu 508 (XY 508, N-inefficient).
• To investigate the influence of varying nitrogen (N) supply levels on root N uptake parameters in both maize hybrids.
• To elucidate the physiological traits contributing to enhanced N acquisition in the N-efficient maize cultivar.

Main Methods:

• Two maize hybrids (ZH 311 and XY 508) were evaluated in two experimental setups: field pots (Exp. I) and hydroponic cultures (Exp. II).
• Plants were subjected to different concentrations of nitrogen (N) fertilizer to simulate varying N availability.
• Key parameters measured included accumulated N, N uptake rates (V_m, V_a, V_max), Michaelis constant (K_m), and root-to-shoot N ratio.

Main Results:

• The N-efficient hybrid ZH 311 consistently showed higher accumulated N and N uptake rates compared to XY 508 across all N supply levels.
• ZH 311 exhibited significantly higher maximum N uptake rate (V_max) and average N uptake rate (V_a), indicating a greater capacity for N absorption.
• Under N deficiency, XY 508 showed a higher root-to-shoot N ratio and Michaelis constant (K_m), suggesting altered N allocation and affinity compared to ZH 311.

Conclusions:

• The N-efficient maize cultivar ZH 311 possesses significantly greater root N uptake ability than the N-inefficient cultivar XY 508, especially under N-deficient conditions.
• Higher V_max and lower K_m values in ZH 311 contribute to superior N affinity, uptake potential, and coordinated N distribution, enhancing N accumulation and yield.
• Efficient N acquisition in ZH 311 is attributed to a higher N uptake rate per root fresh weight under optimal N, and a combination of root size and uptake rate under N deficiency.