Fig. 1.

Effect of external nitrate supply on elongation of primary roots of maize seedlings. Root elongation of maize seedlings pre-grown in varying concentrations of nitrate (0·01 mm, 0·1 mm, 1 mm or 10 mm) for 7 d were used to study relative elongation during a 24-h period. The curve was fitted by an exponential decay with the equation y = (1·03 × 10⁻⁴)e^−2·56x + 63·72. Data were normalized for elongation in 0·01 mm nitrate solution, and represent the mean ± s.e of at least eight roots for each treatment.