Fig. 4

Effects of exogenous melatonin treatment on Na⁺ (A), Cl⁻ (B), K⁺ (C) content and K⁺/Na⁺ ratio (D) of cotton seedlings under salt stress. Control (CK) and salt-treated (S) plants were sprayed with distilled water, while S + MT50, S + MT100, S + MT200, and S + MT500 plants were sprayed with 50, 100, 200, and 500 μM MT, respectively. Different lowercase letters indicate significant differences at the p ≤ 0.05 level