Nitrogen use-inefficient oilseed rape genotypes exhibit stronger growth potency during the vegetative growth stage

There is significant genetic diversity within a species in terms of nitrogen utilization efficiency (NUtE), and genotypes with higher NUtE can help reduce nitrogen (N) fertilization rates and therefore mitigate ecological problems. Determining various characteristic differences in the NUtE of crops is helpful for dissecting the mechanisms of N use efficiency within crop species. In this study, a pot experiment, as well as a hydroponic experiment, was conducted to investigate the differences in oilseed rape biomass, N nutrition traits, N metabolism enzyme activity, root exudates and root RNA expression levels at the vegetative stage between the high and low NUtE genotypes. NUtE was negatively correlated with leaf SPAD values (− 0.341**), N accumulation (− 0.362*) and total biomass (− 0.395**), while there was no significant correlation between NUtE and N content (− 0.150 ns). The root biomass; primary root length and root activity; root N content and accumulation; transpiration rate, and stomatal conductance; root nitrate reductase, glutamine synthetase, and glutamate synthetase activity; the number of alkanes; expression levels of BnNRT1.1 and BnNRT2.1 of the low NUtE genotypes were higher than those of the high NUtE ones. It was concluded that during the vegetative growth stage, compared with the high NUtE oilseed genotypes, low NUtE oilseed genotypes demonstrate higher physiological activity or stronger growth potency at the vegetative growth stage.