Nitrogen availability affects aerenchyma formation and suberization in early root development of soil-grown maize

Nitrogen (N) is a key requirement for crop growth and development, highlighting the importance of root adaptations for enhancing N acquisition. While much attention has been given to root architecture, less is known about how N availability influences root anatomical structures. In this study, we examined one-month-old maize plants grown in soil under two N levels to investigate how N supply affects root anatomy, with a focus on aerenchyma formation and suberization. At this growth stage, no significant differences were observed in shoot and root dry biomass or root length between the two N levels. However, the carbon/nitrogen ratio in both shoot and root tissues was higher under low N conditions, clearly indicating N deficiency. Staining and chemical analyses revealed that, during early nitrogen stress, suberin accumulation was greater in the endodermis than in the exodermis. Specifically, aliphatic suberin levels remained relatively stable, whereas exodermal suberin showed no significant changes under low nitrogen. Additionally, a significant increase in aerenchyma proportion relative to cortical tissue was observed. These findings suggest that under early N limitation, maize adjusts root anatomical traits by prioritizing aerenchyma formation over energy-intensive suberin deposition. This strategy may reduce root metabolic costs, supporting nutrient uptake and growth under suboptimal nitrogen conditions.