Abstract:

To clarify the resistance of high-yield hybrid rice (Oryza sativa L.) at seedling stage to chilly temperature, the photosynthetic characters and protein component of two cultivars, a newly-developed cultivars super-hybrid rice Liangyoupeijiu and a traditional chill-sensitive hybrid rice Shanyou63, were investigated by setting 25℃ as control and 10℃ as low temperature treatment. The results showed that the chlorophyll contents, the consuming oxygen activity of photosystemⅠ (PSⅠ) and oxygen evolution activity of photosystemⅡ (PSⅡ) of thylakoid membrane were decreased obviously in low temperature treatments, so were the absorption spectrum and the emission spectrum of thylakoid membrane at room temperature. The contents of O₂^．- and MDA of Liangyoupeijiu were decreased slightly, but these of Shanyou 63 were increased. Chilly temperature caused an increase of the activity of SOD compared with the control in two cultivars. As compared with the control, CAT activity was higher in Liangyoupeijiu and lower in Shanyou63. All the indexes for Shanyou 63 showed a more distinctive dropping trend. After chilly treatment, the soluble protein content in two cultivars especially in Liangyoupeijiu was significantly higher than those of control. The SDS-PAGE of soluble protein revealed that the protein bands were increased during chilly treatment, but this change did not occur in thylakoid membrane proteins. In the control, almost all parameters investigated except the activities of PSⅠ and PSⅡ were higher in Shanyou 63 than in Liangyoupeijiu, which means that at the seedling stage，Liangyoupeijiu may have stronger resistance to chill-stress than Shanyou63 although the latter has higher photosynthetic function.

Key words: Oryza sativa L, Low temperature, Photosystem, PhotosystemⅡ, Thylakoid membrane