Fig. 4.

Content of ROS and activities of ROS scavenging enzymes of seedling roots of JN177 and SR4 under non-alkalinity and alkalinity stress conditions. a Root O₂ ^•- content in three leaf stage seedlings grown in the absence (CK) or presence of 100 mM alkali salts. b The relative O₂ ^•- content in the roots shown in (a) calculated from mean pixel density. c, d Root content of H₂O₂ (c) and MDA (d). e-i The activity of the ROS scavenging-associated enzymes in the seedling roots including catalase (CAT) (e), superoxide dismutase (SOD) (f), ascorbate peroxidise (APX) (g), glutathione peroxidise (GPX) (h) and peroxidase (POD) (i). Data are given in the form mean ± s.d. The asterisk and double asterisks represent significant difference determined by the Student’s t-test at P < 0.05 (*) and P < 0.01 (**), respectively