Fig. 1
Physiologic responses of oilseed rape to nitrogen (N) limitation stresses. a Growth performance of the rapeseed plants (scale bar = 7 cm) that were hydroponically cultivated under high (9.0 mM) and low (0.30 mM) nitrate (NO3−) conditions for 10 d; (b) leaf SPAD values; (c) leaf anthocyanin concentrations; (d-e) NO3− concentrations in the shoots (d) and roots (e); (f) ratio of shoot NO3− concentrations to root NO3− concentrations; (g-h) activity of NO3− reductase (NR) in the shoots (g) and roots (h); (i-j) activity of glutamine synthetase in the shoots (i) and roots (j); (k) total N concentrations of the whole plants; (l) values of N use efficiency (NUE), NUE = total dry weight/total N content. For (b-l), the rapeseed plants that were grown under 9.0 mM NO3− for 10 d were then transferred to 0.30 mM NO3−, and the shoots and roots were individually sampled at 0 h, 3 h and 72 h. Values denote means (n = 5), and error bars indicate standard error (SE) values. Significant difference was determined by one-way analysis of variance (ANOVA), which was followed by Tukey’s honestly significant difference (HSD) multiple comparison tests using the Statistical Productions and Service Solutions 17.0 (SPSS, Chicago, IL, USA). *: p < 0.05; **: p < 0.01; ***: p < 0.001