Response of NO3 uptake and distribution and nitrogen use efficiency in oilseed rape to limited nitrogen stress

Objectives This research was conducted in order to investigate response of NO3- uptake and distribution to limited nitrogen (N) stress and its influence on nitrogen use efficiency (NUE) in oilseed rape, and supply scientific basis for understanding the physiological and NUE changes under limited-N stress condition. Methods Oilseed rape genotype 814 was used as plant materials, and sand culture experiment was conducted under normal-N (10 mmol/L) and limited-N (3 mmol/L, 1 mmol/L) levels. The response of root characteristics, transpiration, NO3- distribution and assimilation to limited-N stress and its influence on NO3- uptake efficiency and NUE were studied.Results Compared with the normal-N level, NO3- content, total N, root biomass and root uptake area were decreased significantly under limited-N level (3 mmol/L, 1 mmol/L), but ratio of (NO3-) shoot/root and (total N) shoot/root, ratio of root biomass/shoot biomass were increased significantly. Stomatal conductance and transpiration rate were increased significantly in oilseed rape under limited-N stress, which not only stimulated NO3- uptake, but also higher proportion of NO3- distributed from root to shoot; meanwhile, water use efficiency was decreased significantly. There were no significant differences of NR and GS in root and shoot between normal-N and limited-N treatments, chlorophyll content and photosynthesis were decreased significantly, but photosynthetic NUE was increased significantly. Conclusions Total N and biomass of oilseed rape plants were decreased significantly under limited-N stress, but the NUE was increased significantly, which is result from the higher proportion of NO3- distributed from root to shoot and higher photosynthetic NUE under limited-N stress.