Lateral root elongation enhances nitrogen-use efficiency in maize genotypes at the seedling stage

Maize plants show great variation in root morphological response to nitrogen (N) deficit, and such alterations often determine N-use efficiency (NUE) plants. This study assessed genotypic variation in root morphology and NUE in selected 20 maize genotypes with contrasting root system size grown in a semi-hydroponic phenotyping system for 38 days under control (4 mmol L^-1 NO₃ ^- ) and low N (LN) (40 μmol L^-1 ) for 38 days after transplanting.

Maize genotypes exhibited different responses to LN stress in each of the 28 measured shoot and root traits. The 20 genotypes were assigned into one of the three groups: N-efficient (eight genotypes), medium (four genotypes), and N-inefficient (eight genotypes), based on shoot dry weight ratio (the ratio of shoot dry weight at LN and control) ± one standard error. In response to LN stress, the N-inefficient genotypes had significant reduction in biomass production by ~58% in shoots and ~64% in roots, while the N-efficient genotypes maintained their biomass. Under LN supply N-efficient genotypes showed a plasticity response that would result in both sparse lateral branching and increased root elongation as a whole or at each growth strata, and N efficiency positively correlated with lateral or axial root elongation and root elongation at different depths.

The total lateral root length was the main contributor to the improved N foraging and utilization in maize under LN conditions, followed by axial root length. Total lateral root length can be considered in breeding programs for producing maize cultivars with high NUE at the early seedling stage. © 2022 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.