Abstract: After low temperature (4℃ 48 h) treatment oxidative phosphorylation efficiency (ADP/O) and respiratory control ratio (RCR) of mitochondria isolated from chilling- sensitive rice (Qiu Guang, Zao Jin) shoots were lowered and ultrastructure of mitochon- dria in the rice shoots were obviously changed, but no similar changes were observed in the mitochondria from chilling-tolerant rice (Jin Geng 44, Jin Geng 60) shoots after chilling treatment. A “break” at 18℃ had been observed in the Arrhenius plot for succinic oxidase activity by seedling mitochondria of chilling-sensitive rice, while that of mitochondria from chilling-telerant rice shoots exhibited a continuous linear unuction with temperatures between 5–30℃.

Key words: Low temperature, Chilling-sensitive and chilling-tolerant rice, Mitochondrial membrane