Nanopriming with Multi-Walled Carbon Nanotubes Enhances Abiotic Stress Tolerance in Sunflower Seeds

Sunflower (Helianthus annuus L.) is a crop with ornamental and energetic potential, but its propagation is challenged by abiotic stresses such as salinity and water deficit. Ensuring high-quality propagation materials is crucial for healthy plant development. Nanotechnology offers innovative tools to enhance seed performance, stress tolerance, and production efficiency. Among these, carbon nanotubes, a strong, conductive, and thermally resistant material, have shown promise in improving seed quality. This study aimed to evaluate the effects of nanopriming with multi-walled carbon nanotubes (MWCNTs) on the physiological and biochemical performance of sunflower seeds under accelerated aging and stress conditions. Seeds were treated with 100, 200, or 400 mg·L−1 MWCNTs, and parameters such as germination percentage, seedling growth, pigment profile, and oxidative stress indicators were analyzed. The 200 mg·L−1 concentration enhanced germination, root and shoot development, and antioxidant enzyme modulation, while the 400 mg·L−1 dose increased reactive oxygen species, indicating toxicity. Under saline and drought-like conditions, nanopriming with 100–200 mg·L−1 mitigated oxidative damage more effectively than hydropriming. MWCNTs also influenced pigment synthesis, affecting chlorophyll and carotenoid levels. These findings support the potential of carbon nanotube-based nanopriming to improve seed vigor and stress tolerance in sunflower cultivation, though further environmental safety assessments are required.