Figure 4

Activities (U/g fresh weight (FW)) of the antioxidant enzymes superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) in cotton leaves under different types of salt–alkali stress (NaCl (CS), Na₂SO₄ (SS), and Na₂CO₃ + NaHCO₃ (AS)). Columns with bars represent the mean ± standard error (n = 3). Asterisks indicate a significant difference between the control (CK) and the salt–alkali stress (*p < 0.05; **p < 0.01). (a–c) indicate the SOD in cotton leaves under NaCl, Na₂SO₄, and Na₂CO₃ + NaHCO₃ stress, respectively. (d–f) indicate the POD in cotton leaves under NaCl, Na₂SO₄, and Na₂CO₃ + NaHCO₃ stress, respectively. (g–i) indicate the CAT in cotton leaves under NaCl, Na₂SO₄, and Na₂CO₃ + NaHCO₃ stress, respectively.