The landscape application of sweet osmanthus (Osmanthus fragrans) with flower fragrance and high ornamental value is severely limited by salinity stress. Gamma irradiation applied to seeds enhanced their tolerance to salinity stress as reported in other plants. In this study, O. fragrans ‘Huangchuang Jingui’ seeds were pretreated with different doses of gamma irradiation, and tolerance of the seedlings germinated from the irradiated seeds to salinity stress and the changes of reactive oxygen species (ROS) production and ROS scavenging systems induced by gamma irradiation were observed. The results showed that seed pretreatment with different doses of gamma irradiation enhanced the tolerance of sweet osmanthus seedlings to salinity stress, and the positive effect induced by gamma irradiation was more remarkable with the increase of radiation dose (50–150 Gy). The pretreatment with high-dose irradiation decreased O₂⁻ production under salinity stress and mitigated the oxidative damage marked by a lower malondialdehyde (MDA) level, which could be related to the significant increase of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) activities in the seedlings germinated from the irradiated seeds compared to the corresponding control seedlings. In addition, the accumulation of proline in the irradiated seedlings may contribute to enhancing their tolerance to salt stress by the osmotic adjustment. The study demonstrated the importance of regulating plant ROS balance under salt stress and provided a potential approach to improve the tolerance of sweet osmanthus to salt stress.

Pollen germination of Lilium davidi var. unicolor and Gladiolus × hybridus after storage at −80 °C and 4 °C were investigated in relation to the changes in the carbohydrate content. Germination was found to be directly related to the type of carbohydrate and its content in the pollen grains. With higher sucrose, glucose and fructose contents, L. davidi pollen showed higher germination than G. × hybridus pollen and maintained higher germination rate during storage. The total sugar content of both species preserved at −80 °C was higher than those preserved at 4 °C, suggesting that the pollen grains maintained their viability much longer at −80 °C than at 4 °C. The increase in the viability can be correlated to the increase in the starch and sucrose content especially when the pollen was stored at 4 °C.