Fig. 4

The expression levels of the genes involved in nitrogen metabolism in roots under different N treatments. Means denoted by different letters are significantly different at P < 0.05 as determined by Duncan's multiple range test. N0, N1, N2 and N3 represent 0, 4, 8 and 16 mmol L-1, respectively. J26 and X32 represent cultivar Jishu 26 and Xushu32, respectively.