PMC

The activities of NR, GS, and GOGAT in leaves (A–C) and roots (D–F) treated with CK (0 mg·L⁻¹ fulvic acid), FA1 (60 mg·L⁻¹ fulvic acid), FA2 (120 mg·L⁻¹ fulvic acid), FA3 (180 mg·L⁻¹ fulvic acid), or FA4 (240 mg·L⁻¹ fulvic acid). Vertical bars on the histograms indicate standard deviations of three replications. Different letters indicate statistically significant differences (p < 0.05).

(a) Total antioxidant capacity (TAC); (b) glutathione peroxidase (GPx); (c) superoxide dismutase (SOD); (d) glutathione (GSH) activities; (e) catalase (CAT); (f) lipid peroxidation (MDA) of frozen‐thawed buffalo semen after supplementation of different concentrations of L‐proline (Lp) and fulvic acid (FA) to the semen extender. Control (c): Tris‐based extender without antioxidant; Lp‐10: Tris‐based extender + L‐proline (10 mM); Lp‐20: Tris‐based extender + L‐proline (20 mM); Lp‐40: Tris‐based extender + L‐proline (40 mM); Lp‐60: Tris‐based extender + L‐proline (60 mM); Lp‐80: Tris‐based extender + L‐proline (80 mM); FA‐0.2: Tris‐based extender + fulvic acid (0.2%); FA‐0.5: Tris‐based extender + fulvic acid (0.5%); FA‐0.8: Tris‐based extender + fulvic acid (0.8%); FA‐1.1: Tris‐based extender + fulvic acid (1.1%); FA‐1.4: Tris‐based extender + fulvic acid (1.4%); FA‐1.7: Tris‐based extender + fulvic acid (1.7%). Different superscripts within the same row demonstrate significant differences (p ≤ 0.05; mean ± SEM).

Sorbitol concentrations in seedling leaves (A) and roots (C) and sucrose concentrations in seedling leaves (B) and roots (D) treated with CK (0 mg·L⁻¹ fulvic acid), FA1 (60 mg·L⁻¹ fulvic acid), FA2 (120 mg·L⁻¹ fulvic acid), FA3 (180 mg·L⁻¹ fulvic acid), or FA4 (240 mg·L⁻¹ fulvic acid). Vertical bars on the histograms indicate standard deviations of three replications. Different letters indicate statistically significant differences (p < 0.05).

¹³C accumulation of seedlings (A), organ ¹³C distribution rate (B), and root MdSOTs and MdSUTs gene expression (C–K) treated with CK (0 mg·L⁻¹ fulvic acid), FA1 (60 mg·L⁻¹ fulvic acid), FA2 (120 mg·L⁻¹ fulvic acid), FA3 (180 mg·L⁻¹ fulvic acid), or FA4 (240 mg·L⁻¹ fulvic acid). Vertical bars on the histograms indicate standard deviations of three replications. Different letters indicate statistically significant differences (p < 0.05).