Grain Nitrogen Source Changes over Time in Maize: A Review

Abstract

Understanding the sources of grain N uptake (Grain N) in maize (Zea mays L.) and especially the trade‐off between reproductive‐stage shoot N remobilization (Remobilized N) and reproductive‐stage whole‐plant N uptake (Reproductive N) is needed to help guide future improvements in yield and N use efficiency (NUE). Therefore, a literature review was performed to investigate the knowledge gap concerning changes over time in Grain N sources and on N partitioning to the grain and stover plant fractions at maturity. The synthesis–analysis was based on 100 reports, which were divided into two time intervals: (i) research conducted from 1940 to 1990—“Old Era”—and (ii) research conducted from 1991 to 2011—“New Era.” The most remarkable results were (i) Grain N concentration was the main parameter that has changed over time, (ii) Reproductive N contributed proportionally more to Grain N for the New Era while Reproductive N and Remobilized N contributed equally to Grain N for the Old Era, (iii) Remobilized N was primarily associated with vegetative‐stage whole‐plant N uptake (Vegetative N), which was constant across eras, although the proportion of the Remobilized N itself seems to be driven by the ear demand, (iv) complex plant regulation processes (source:sink) appeared to influence Reproductive N, and (v) stover N concentration gains mirrored the grain N concentration as the plant N uptake increased at maturity in both eras. This new appreciation for the changes over time may assist directed selection for yield and NUE improvements.

Diverse concepts of breeding for nitrogen use efficiency. A review

“…The N remobilization process starts from stem and older, lower leaves to sustain the leaf %N of the upper layers, especially around the ear leaf, but is also affected by other factors such as water and light stress. The ears have very high concentrations of nitrogen during their initiation but that nitrogen is diluted rapidly by starch accumulation during grain filling, although the total amount of nitrogen in the ears is increasing rapidly (Ciampitti and Vyn 2013). These authors concluded that grain N is the result of the interplay between the following aspects: (1) shoot N remobilized at reproductive stage and whole-plant N uptake at reproductive stage, (2) the ratio between the nitrogen in the grains and the nitrogen in the whole plant (NHI), and (3) grain yield and %grain N.…”

“…Ciampitti and Vyn (2013) compared older maize cultivars (released before 1990) and more recent cultivars and concluded that with increasing yield over time, grain N concentration has decreased. They also concluded that for the modern cultivars, reproductive N contributed relatively more to grain N whereas for the older cultivars, reproductive and remobilized N contributed equally to grain N. The remobilized N was primarily associated with wholeplant N uptake (vegetative N), which was constant over time of breeding, although the proportion of the remobilized N itself seemed to be driven by the ear demand, whereas the reproductive N seemed to be influenced by complex plant regulation processes (source/sink).…”

“…Nitrogen use efficiency (NUE) comprises three key components: the nitrogen uptake efficiency (NUpE), the nitrogen utilization efficiency (NUtE) in producing biomass, and the nitrogen harvest index (NHI) (Masclaux-Daubresse et al 2010;Ciampitti and Vyn 2013). NUtE and NHI can be merged into one component: the utilization efficiency for harvestable products.…”

Rendimiento de grano y características fenotípicas de maíz: efecto de ambiente y dosis de fertilización

“…Nitrogen mobilizes through the stem and leaf (Ciampitti and Vyn, 2013). Adequate supply of nitrogen improves grain yield of maize, mainly in the increase of grain number (Uribelarrea et al, 2004;Khaliq et al, 2009).…”

Living to Die and Dying to Live: The Survival Strategy behind Leaf Senescence

“…Remobilized N, an important contributor throughout plant growth, is derived from N taken up by the plant during the vegetative period. However, modern maize varieties also utilize N taken up by the plant during the reproductive phase, which is transported directly to the grain (Ciampitti and Vyn, 2013).…”