Uptake and uptake kinetics of nitrate, ammonium and glycine by pakchoi seedlings ( Brassica Campestris L . ssp. Chinensis L. Makino )

•Glycine uptake and uptake rate were higher than inorganic N at high N concentration.•N uptake efficiency had a negative correlation with N concentration.•Active uptake dominated pakchoi glycine uptake.•More than 20% of total N was taken up passively at high N concentration.•Glycine uptake capacity was comparable with the inorganic N.