Preliminary studies observed a lower growth activity during the vegetative stage with higher growth attributes at the pod-filling stage among the high nitrogen (N) utilisation efficiency (NUtE) oilseed rape (Brassica napus L.) genotypes, compared with the low NUtE genotypes. Therefore, we hypothesised that there would exist a critical growth stage when distinctive phenotypic traits are exhibited to regulate yield formation and NUE. A field experiment and a hydroponic culture were conducted to characterise the differences in shoot and root physiological indicators of the high and low NUtE oilseed rape genotypes at seedling, bud, bolting, flowering and pod-filling stages. We found that flowering was the critical period when the reverse growth habit occurred between high and low NUtE genotypes. The high NUtE genotypes displayed larger values of root traits, stronger N uptake kinetics parameters, higher activity of leaf glutamine synthetase (GS) and glutamate synthetase (GOGAT), larger SPAD values and net photosynthetic rate, ultimately leading to higher seed yield and NUE. Our results indicate that flowering is the critical growth stage to distinguish the high from low NUtE oilseed rape genotypes, and plant breeders may focus on selecting root and shoot phenotypic traits from flowering stage onwards to achieve both high yields and NUE for oilseed rape genotypes.

初步研究发现，高氮（N）利用油菜（甘蓝型油菜）的营养期中，营养期的生长活性较低，而荚果期的生长特性较高。L.）基因型，与低NUtE基因型相比。因此，我们假设当表现出独特的表型性状来调节产量形成和NUE时，将存在一个关键的生长阶段。进行了田间试验和水培培养，以表征高，低NUtE油菜油菜基因型在苗，芽，抽,、开花和荚果期的茎和根生理指标的差异。我们发现开花是关键的时期，当逆向生长习惯发生在高和低NUtE基因型之间时。高NUtE基因型表现出更大的根系性状值，更强的氮吸收动力学参数，更高的叶片谷氨酰胺合成酶（GS）和谷氨酸合成酶（GOGAT）活性，更大的SPAD值和净光合速​​率，最终导致更高的种子产量和NUE。我们的结果表明，开花是区分高和低NUtE油菜油菜基因型的关键生长阶段，植物育种者可能着重于从开花期开始选择根和芽表型性状，以实现油菜油菜基因型的高产量和NUE。