Abstract: The hybrid rice and their parental lines were exposed to the low temperature of 0, –2, –4℃ for 16 hours. The activities and isoenzymic patterns of SOD in various organelles of rice seedlings were studied. The experimental results are as follows: 1. This enzyme was located mainly in the cytosol (96%), the rest in mitochondria (2%) and chloroplasts (2%). The electrophoretogram showed that there were four isoenzymic activity bands of SOD in cytosol and mitochondria, three bands in chloroplasts. One band with relatively slow migrating rate was Mn-SOD isoenzyme and others were Cu-Zn SOD isoenzymes. 2. The change of SOD activities was obvious in the plant pretreated at –2℃ and –4℃ temperature for 16 hours. The effect of low temperature on SOD in various organelles was different. The sensitivity of SOD in chloroplasts was higher than those in mitochondria and cytosol. The two activity bands of Cu-Zn SOD isoenzyme in chloroplasts and mitochondria also decreased at low temperature. 3. The response of SOD activities in chloroplasts from hybrid and parent of rice to low temperature showed that the cold tolerance of hybrid progeny was similar to that of the material lines.

Key words: Rice seedling, Low temperature stress, superoxide dismutase