Fig. 3

Relationship between CTK concentration and nitrate reductase activity in the very fine (A) and fine (B) roots of Gossypium hirsutum. Fine roots are those with diameter between 0.1 and 2 mm, while very fine roots are those with diameter less than 0.1 mm. The regression models are NR = 2.54 × CTK – 19.34 (R² = 0.54, P < 0.001) and NR = 44.29 – 1.58 × CTK (R² = 0.49, P < 0.002) for the very fine and fine roots, respectively