Selenium Seed Pre-Sowing Treatment Duration Modulates Germination and Antioxidant Responses of Industrial Hemp cv. Felina 32 Under Drought Stress

Drought stress can strongly limit seed germination and early seedling development, while seed pre-sowing treatment may improve plant responses during these critical growth stages. This study evaluated the effects of hydropriming treatment and selenium (Se) pre-sowing treatment on germination, seedling growth, biomass accumulation, and biochemical responses of industrial hemp (Cannabis sativa L.) cv. Felina 32 under PEG-induced osmotic stress. Seeds were hydroprimed with distilled water or primed with sodium selenate (40 µmol L−1 Se) for 30, 60, 90, or 120 min, while dry seeds served as the control. Osmotic stress was induced using 0, 2.5, 5.0, and 7.5% polyethylene glycol (PEG 6000). Germination remained high across treatments (95–98%), although increasing PEG concentration significantly reduced seedling growth and vigor. Total seedling length decreased from 13.52 cm at 0% PEG to 10.07 cm at 7.5% PEG, while fresh mass declined from 0.142 to 0.096 g seedling−1. At 7.5% PEG, Se 60 seedlings reached 10.95 cm compared with 9.38 cm in the non-primed control, while Se 90 maintained a fresh mass of 108 mg compared with 93 mg seedling−1 in the control. Biochemical responses were also treatment-dependent, with pronounced changes in proline, total phenolic content, and antioxidant capacity under increasing stress. Generally, Se pre-sowing treatment did not produce a uniform response across all conditions, but specific pre-sowing treatment durations, particularly 60–120 min, showed potential to modulate early hemp seedling responses to osmotic stress.