In this study, the effects of sufficient and deficient soil N on the growth and physiology performance of maize inbreds (B73, Mo17, Sids7 and Sids63) and hybrids (B73 × Mo17 and Sids7 × Sids63) were simultaneously monitored. This was done at rapid growth phase to have better understanding of the inbred/hybrid growth and physiological relationships. B73 and Sids7 maintained superior growth over Mo17 and Sids63. Their superiority was associated with larger leaf area, lower SLA, high levels of photosynthetic pigment, sucrose, ammonia-N, amino-N, total N and NUE under both N treatments. Hybrids surpassed their parental inbreds in growth and leaf features under the same N rates. Sids7 × Sid63 had higher biomass and faster growth rate than B73 × Mo17 and its superiority was associated with higher leaf area, smaller SLA and greater leaf N. N limitation reduced growth and physiological components in all genotypes, although at significantly different magnitudes. In contrast, limited N induced different levels of starch accumulation in all genotypes indicating variable degrees of disruption of source-sink relationships. The improved growth of B73, Sids7 and the hybrids under sufficient and limited N supply is shaped by a combination of larger leaf area, smaller SLA, higher leaf N, efficient resource utilization, and maintaining proper source-sink relations.