Figure 6.

Differences in NRA/NA (a), GSA/NA (b), NH₄⁺ content (c) and soluble protein content (d) between the two types at the same nitrogen level and same leaf biomass accumulation condition. NA: Nitrogen application level; NRA/NA: Ratio of nitrate reductase activity to nitrogen application level; GSA/NA: Ratio of glutamine synthetase activity to nitrogen application level. NL_G1: low nitrogen level, HD; NL_G2: low nitrogen level, Z100; NL_Y1: low nitrogen level, TN90; NL_Y2: low nitrogen level, TN86; NH_Y1: high nitrogen level, TN90; NH_Y2: high nitrogen level, TN86. Error bars indicate standard error of the means (n = 3). Symbols ** ¹ and * ¹ indicate that the significant differences between flue-cured tobacco and burley tobacco at the same nitrogen application are at 0.01 and 0.05, respectively. Symbols ** ² indicate that the significant differences between flue-cured tobacco and burley tobacco at the same leaf biomass accumulation condition are at 0.01, respectively.