A comprehensive analysis of root morphological changes and nitrogen allocation in maize in response to low nitrogen stress

Abstract

The plasticity of root architecture is crucial for plants to acclimate to unfavourable environments including low nitrogen (LN) stress. How maize roots coordinate the growth of axile roots and lateral roots (LRs), as well as longitudinal and radial cell behaviours in response to LN stress, remains unclear. Maize plants were cultivated hydroponically under control (4 mm nitrate) and LN (40 μm) conditions. Temporal and spatial samples were taken to analyse changes in the morphology, anatomical structure and carbon/nitrogen (C/N) ratio in the axile root and LRs. LN stress increased axile root elongation, reduced the number of crown roots and decreased LR density and length. LN stress extended cell elongation zones and increased the mature cell length in the roots. LN stress reduced the cell diameter and total area of vessels and increased the amount of aerenchyma, but the number of cell layers in the crown root cortex was unchanged. The C/N ratio was higher in the axile roots than in the LRs. Maize roots acclimate to LN stress by optimizing the anatomical structure and N allocation. As a result, axile root elongation is favoured to efficiently find available N in the soil.

Use of genotype‐environment interactions to elucidate the pattern of maize root plasticity to nitrogen deficiency

“…Low nitrogen stress increased root dry weight and reduced shoot growth on average (except groups 3 and 4), thereby causing an increase in R.S (Figure ). In agreement with the previous studies (Chun et al ; Abdel‐Ghani et al ; Gao et al ), enhancement of R.S is an adaptive response to facilitate the capture of more N from the environment. LN stress could also increase root length for AR, LR, and PR.…”

“…LN stress could also increase root length for AR, LR, and PR. The increase in ARL under LN stress was exponentially correlated to decreases in shoot nitrogen concentration ( r 2 = 0.916) and the shoot carbon/nitrogen ratio ( r 2 = 0.913) (Gao et al ). The changes in shoot concentration (or increases in shoot carbon/nitrogen ratio) may act as an internal nitrogen‐status signal to regulate the response of AR growth to LN stress.…”

“…Maize root produces multiple phenotypes responded to different N levels (Table ; Figure B; Chun et al ; Liu et al ; Abdel‐Ghani et al ; Gao et al ). Although a minor variation of root growth in response to N availability was determined, this study could identify nine QTLs with a significant Q × E effect (Table ), suggesting the presence of genetic loci contributing to the phenotypic plasticity to LN.…”

MORPHOGENESIS AND SECONDARY METABOLITES PRODUCTION IN THE MEDICINAL PLANT Castilleja tenuiflora Benth. UNDER NITROGEN DEFICIENCY AND STARVATION STRESS IN A TEMPORARY IMMERSION SYSTEM

“…Here we observe that generated roots showed changes in their architecture; they were more numerous and 30% longer than those of control plants (Fig 1h-k). A similar behaviour was observed in plants of Matricaria chamomilla, Arabidopsis thaliana and Zea mays that were grown under N starvation, where plant matter was strongly affected and root length was greater than shoots, as compared with control (Kovacik and Backor 2007; Krapp et al 2011;Gao et al 2015). In contrast, Castilleja tenuiflora shoots cultured in bioreactor under 1.32 mM N deficiency showed strongly growth and fresh matter reduction but, there was no root generation (Medina-Perez et al 2015).…”

Hardpan and maize root distribution under conservation and conventional tillage in agro-ecological zone IIa, Zambia

“…Durieux et al (1994) showed that total root weight declined as N application increased. High N supply appears to reduce root elongation (Wang et al, 2008); whereas N deficiency increases axial root lengths, although with a reduced number of roots (Chun et al., 2005;Gao et al, 2015). Root branching is stimulated by ample N supply (Eghball et al, 1993).…”