关键词: 桂花, 叶绿素荧光动力学, 光系统Ⅱ, 光抑制, 低温胁迫

Abstract: In order to explore the photosynthetic mechanism of Osmanthus fragrans suffering from cold damage during overwinter period, this study took fluorescence kinetics as means to monitor the changes in photosystemⅡ(PSⅡ) behavior characteristics of Osmanthus fragrans leaves in Beijing region during overwinter period. The results showed that the initial fluorescence (F0), the biggest photochemical efficiency of PSⅡ(Fv/Fm), effective quantum yield of PSⅡ(yield) and electron transport rate of PSⅡ(ETR) decreased with the temperature falling in winter, indicating the light harvesting antenna system of Osmanthus fragrans leaves was destroyed during the overwintering period, therefore inhibited the initial reaction of photosynthesis. The leaves could reduce the excitation voltage of PSⅡ reaction center by decreasing energy captured by the antenna system. In addition, the photochemical quenching (qP) of Osmanthus fragrans leaves was consistently at a high level, indicating that PSⅡ reaction center could maintain a higher degree of openness in overwinter period, so as to reduce the damage of PSⅡ reaction center by excitation energy accumulation in donor side of PSⅡ. While, the non photochemical quenching (NPQ) remarkably decreased with the temperature falling. Thus, it could be inferred that Osmanthus fragrans could resist low temperature stress in winter mainly through the heat dissipation other than the antenna system.

Key words: Osmanthus fragrans, chlorophyⅡ fluorescence kinetics, photosystemⅡ, photoinhibition, low temperature stress