Seasonal acclimation of superoxide anion production, antioxidants, IUFA, and electron transport rates in chloroplasts of two Sabina species

Chloroplasts are the main source of reactive oxygen species (ROS) production in plant, better balance between productions and scavenging of ROS in chloroplasts plays an important role in development of freezing tolerance. In the present study, two evergreen woody plants, Sabina przewalskii Kom. scattered at higher altitudes, Sabina chinensis (Lin.) Ant. distributed at lower altitudes, were used to investigate seasonal variation patterns in superoxide anion production, antioxidants, and index of unsaturated fatty acid (IFUA) during the natural temperature variations. IFUA, GSH, AsA and Car content in chloroplasts were all negatively correlated mean air temperature in both Sabina species, which were regarded to be useful to maintenance of membrane fluidity and function and improvement of antioxidative ability during cold stress. However, positive correlation of air temperature with superoxide anion generation was also found in two Sabina trees, which also suggested that decreased superoxide anion generation was related to increased antioxidants in winter. Compared with S. chinensis (Lin.) Ant., there were significantly higher antioxidants and lower quantity of superoxide anion in S. przewalskii Kom., however, there was higher unsaturated fatty acids ratio in S. chinensis (Lin.) Ant. than S. przewalskii Kom. These results together suggested that the regulations of superoxide anion production and antioxidants in chloroplasts are critical to increase in cold-tolerance between two Sabina evergreen trees; however, high unsaturation lipid level is only one of the factors that maintain the membrane function of chloroplasts for cold-tolerance during decreasing temperature.