Condicionamento com peróxido de hidrogênio em sementes de Corymbia citriodora

Abstract

Corymbia citriodora is a species of great importance to the Brazilian forestry sector, commonly cultivated across different soils and regions, even those with low nutrients and water resources. However, abiotic stresses such as salinity represent a growing threat to its germination, establishment, and productivity. Therefore, the present study investigated the potential of hydrogen peroxide (H₂O₂) as an osmotic priming agent to improve germination rates, seedling characteristics, and salinity tolerance in C. citriodora. The experiment was conducted under controlled conditions using a completely randomized design in a factorial scheme, with five replicates of twenty seeds. Seeds were pre-treated with H₂O₂ (0, 100, 200, and 400 mM). Seedlings were grown for 14 days under control conditions (0) and germinated under stress induced by sodium chloride (NaCl) (0, 75, and 150 mM). Salt stress significantly inhibited (P < 0.05) the germination percentage, seed vigor index, root length, and chlorophyll content. Conversely, pre-treated seeds showed significant improvement (P < 0.05) in germination speed, seed vigor indices, root length, and anthocyanin content. Given the uniform germinative response among H₂O₂ doses, the 100 mM dose and hydropriming (to isolate the H₂O₂ effect) were selected for the biochemical study under a factorial scheme (2 priming agents × 4 soaking times + control). Neither priming treatment was able to induce over-expression of antioxidant enzymes (SOD, CAT, APX) or decrease lipid peroxidation (MDA). On the other hand, the priming agents were efficient in reducing endogenous H₂O₂ levels, indicating that the protective effect stems from a fine-tuning of the redox state