The Physiological Mechanisms and Hurdles of Efficient Water-Nitrogen Utilization in Maize Production: A Review

Abstract

Maize (Zea mays L.) is one of the most important staple food crops globally. One-third of global maize production is located in areas with high or extreme water scarcity and concurrently faces the challenge of low nitrogen use efficiency. Therefore, achieving synergistically high-efficiency water and nitrogen utilization in maize production is of great significance for agricultural sustainable development and global food security. In recent years, more articles have focused on the physiological mechanisms and management practices of efficient water and nitrogen utilization in maize. Unfortunately, there is a relative scarcity of research on the interactive effects between water and nitrogen on the development of young ears, which plays a crucial role in maize productivity. By compiling the most pertinent publications, this review endeavors to consolidate the existing knowledge on the interactive effects between water and nitrogen on maize production. Moreover, it advances potential physiological mechanisms and strategies for high-efficiency water and nitrogen utilization in terms of root system functioning, phytohormones, metabolism, and organ development. The changes in the availability of water and nitrogen have a significant impact on the development of young ears during the critical period, which in turn directly determines the grain number per ear and grain weight.

Keywords: cytokinin; deficit irrigation; ear development; floret primordium; maize; nitrogen; signal transduction.

Figure 1

Maize young ear differentiation during the critical period and its potential impact on grain number and grain weight (modified from Liu et al., 2021 [30] and 2022 [31]).

Figure 2

Model depicting the cytokinin-mediated transmission of nitrogen signals from the root system to the shoot. DMAPP: dimethylallyl pyrophosphate; ATP: adenosine triphosphate; ADP: adenosine diphosphate; AMP: adenosine monophosphate; IPT: isopentenyl transferase. The question in the circle represents the unclear mechanism of nitrogen perception and signal generation, and that in the rounded rectangle relates to regulatory mechanism of loading and unloading during the long-distance transport of cytokinin. The solid double arrows represent signal perception. The single solid arrows represent promoting effects or substance transformation. The dotted arrows represent positive correlation.

Figure 3

A schematic diagram illustrating cytokinin–nitrogen signaling networks governing ear differentiation, grain set, and yield potential in maize. GS: glutamine synthetase; IPT: isopentenyl transferase; RR: response regulator; 6-BA: 6-benzylaminopurine, that is, an artificially synthesized cytokinin-type plant growth regulator; INCYDE: a cytokinin dehydrogenase inhibitor. The red and blue arrows represent promotion and inhibition, respectively, while the black arrows represent substance transformation.