No abstract

Sunflower (Helianthus annuus L.) is a relevant oilseed species used as feed in human and animal nutrition and in multiple industrial applications. However, oilseeds need to deal with the loss of vigor when used as a propagule, due to loss of seed physiological quality (viability and vigor) caused by deterioration events. We have evaluated in the present study the effects of seeds priming techniques (water, ascorbic acid, and sodium nitroprusside) on vigor, germination, antioxidant enzymes and membrane integrity of stored sunflower hybrid HELIO 251 seeds. Germination parameters showed that non-primed seeds (control) delayed germination in almost 72 h while all primed seeds germinated 100% in 24 h. Electrolyte leakage and malondialdehyde levels were higher in non-primed seeds indicating higher degree of membrane damage. An increase in the activity of catalase and ascorbate peroxidase was also observed after 8 h of imbibition of primed seeds compared to non-primed seeds. Regarding superoxide dismutase, there was no significant differences between treatments after 8 h of imbibition, whereas the highest activity was after 24 h of imbibition in non-primed seeds. Therefore, it can be concluded priming with ascorbic acid or sodium nitroprusside exhibited better performance in germination of stored sunflower seeds, probably resulting from lower accumulation of reactive oxygen species and consequent reduced oxidative damage due to an efficient antioxidant enzyme system.

No abstract

The maintenance of seed viability is widely studied since preserving the physiological characteristics that will allow efficient germination and adequate field occupation is broadly pursued. However, even under optimal storage conditions, the aging process is inherent to the seed’s life. In order to understand the effects of storage under low and normal oxygen conditions, this work sought to evaluate the physiological responses of two seed lots of two sunflower hybrids stored under different oxygen availability (normoxia and hypoxia) over a 360-day period. Aiming to investigate the effects of storage, the activities of the enzymatic antioxidant metabolism, hydrogen peroxide and MDA content, and the performance of viability, and vigor tests (tetrazolium test and electrolyte leakage) were performed with the stored seeds every 60 days. The hypoxia conditions were not able to keep seed viability over time, probably affecting negatively the embryonic axis. Throughout the evaluations, the viability tests demonstrated that the storage in the two experimental conditions was not able to contain the aging of the seeds. The increased content of H2O2 and MDA, associated with the enhanced electrical conductivity over time, indicate that there were losses by lipid peroxidation and that the aging process was not contained by storage under low oxygen availability.