The effect of temperature and treating time on the expression of sterility of CMS 3411-7 in Chinese cabbage Petsai with Polima cytoplasm was observed with alternat ing temperature, constant temperature in light growth incubator and alternating temperature in nature condit ion. The results showed that range of temperature affecting the sterility of CMS 3411-7 was wide, it occurred sterility changeover or fluctuation in constant temperature 3- 15℃, the range of 8/ 4℃ to 14/ 10℃ ( day/ night, that is daily mean temperature 6- 12℃ ) is the effective temperature. At constant temperature
6 ! , the value of changeover of CMS 3411-7 got grade 2 in 3- 5 days treatment , and the changeover of it was enhanced while the treating time prolonged ( from 3 to 9 days) . At constant temperature 9℃, there was a largest changeover in 6 days treatment compared with that in 3 or 9 days treatment. At al ternating temperature 14/ 10℃, the intensity of changeover of sterility is not depended upon the treating time. At 17/ 13℃ long treating time inhibited the changeover of sterility. In addition, although there was large difference between the begin or the end of changeover of sterility in difference treatment, the time of significant changeover of sterility was still concentrated and stable in 10- 27 days after temperature treatment. Because the changeover of sterility happened in 8/ 4℃- 17/ 13℃ in only 3
days treatment , it seems that 3 days treatment in that condition is enough to induce the gene of changeover of sterility, whether the time shorter than 3 days may induce it still need future study.