Abstract: Three indica rice restorer lines, Mianhui725, Shuhui527, Shuhui881, an American rice　variety Lemont and a javanica rice Xiangdali were crossed with Japanese japonica Kitaake.Studies of photosynthetic characteristics indicated that under strong photosynthetic flux density　(PFD), the net photosynthetic rate (Pn) that 5 F1 hybrids reached was significantly higher than that of their own parents or one of them. According to the findings about stomatal conductance (Gs) and intercellular CO2 concentration (Ci), differences in Rubsico activity in leaves might exist among parents and hybrids. During the investigation of photosynthetic indexes such as Quantum efficiency (j), Carboxylation efficiency （CE） and CO2 compensation point (G), the intersubspecific hybrids F1 Mianhui725/Kitaake, Shuhui527/Kitaake, and Shuhui881/Kitaake had significant photosynthetic heterosis as compared with the intersub-subspecific hybrids Xiangdali/Kitaake (javanica/japonica)、Lemont/Kitaake (japonica/japonica). Moreover, Shuhui881 had some japonica consanguinity, which made Shuhui 881/Kitaake with less photosynthetic heterosis than Mianhui725/Kitaake or Shuhui527/Kitaake. Therefore, the photosynthetic heterosis of 5 F1 hybrids existed in their genetic differences, and the typical intersubspecific hybrids Mianhui725/ Kitaake and Shuhui527/Kitaake were better than others.

Key words: Rice, Genetic distance, Net photosynthetic rate, Photosynthetic characteristics