Fig. 6
Effect of low temperature on nitrate reductase (NR) and nitrite reductase (NiR) activities of cucumber seedlings. (A) NRAmax, the maximum activity of nitrate reductase; (B) NRAact, the actual activity of nitrate reductase; (C) NiR activity, the activity of nitrite reductase. Error bars represent the standard error of the mean (n = 3). Different lower-case letters indicate a significant difference (P < 0.05)