Abstract:Reactive oxygen species (ROS) are present in all aerobic organisms, but the seed deterioration processes can increase its production. Oxidative stress caused by higher endogenous ROS may cause irreparable damage to cells, leading to the loss of seed viability. Considering that the enzyme superoxide dismutase (SOD) composes the first enzymatic antioxidant defense mechanism, this study aimed to evaluate zygotic embryos of Araucaria angustifolia recalcitrant seeds during storage regarding changes in SOD activity. Besides, some of the major alterations resulting from oxidative stress, e.g., lipid peroxidation and changes in proteins and DNA integrity were also measured. Approximately, 7 000 seeds were harvested from a population in Southern Brazil and stored for 180 days under laboratory (L, laboratory temperature), refrigeration (R, 5 ± 1 °C) and freezing (F, -18 ± 1 °C) conditions. The analysis of lipid peroxidation through TBARS levels, SOD activity, protein profile by electrophoretic separation, and integrity of genomic DNA were performed at 0, 60, 120, and 180 days of storage. The results revealed an increase in lipid peroxidation and SOD activity, especially during the L storage, a condition in which there was an extensive degradation of proteins. Some proteins (i.e., 45, 32, and 31 kDa) were expressed only in embryos stored under R and F conditions. No damage was observed in the nuclear DNA integrity for the evaluated period of seed storage at R and F conditions. The F samples maintained the biochemical traits of interest throughout the storage period, with the exception of the protein profile. However, such changes are limiting for the maintenance of seed viability. In conclusion, R storage can be indicated to delay the metabolic feature alterations that occur when seeds are exposed to conditions of natural ambient after harvest, extending the conservation period of A. angustifolia seeds. Rev. Biol. Trop. 63 (4): 1185-1196. Epub 2015 December 01.Key words: Brazilian pine, recalcitrant seeds, seed deterioration, oxidative stress, superoxide dismutase.Araucaria angustifolia (Bert.) O. Ktze is a native conifer species from the Atlantic Rain Forest (Veloso, Rangel Filho, & Lima, 1991) in South Brazil. In its area of natural occurrence this species is one of the most important trees in ecological, economic, and social aspects (Auler, Reis, Guerra, & Nodari, 2002;Vibrans et al., 2011; Rosenfield & Souza, 2013). Among the trees of tropical origin, many species produce recalcitrant seeds, such as some of the Araucariaceae family (Song, Berjak, Pammenter, Ntuli, & Fu, 2003), including A. angustifolia (Balbuena et al., 2011 FariasSoares, Burrieza, Steiner, & Guerra, 2013), which rapidly germinate after dispersion (Löwe & Dillenburg, 2011).Seeds reach their maximum physiological quality after the completion of reserve substances allocation at physiological maturity time. From this point, the deterioration process begins, when several metabolic changes are apparent. But in recalcitrant seeds there is a patter...