This study was designed to research the photosynthetic capacities of the flag leaf sheathes and photosynthetic products' distribution of the leaf sheathes of Liangyoupeijiu, using Liangyoupeijiu (super hybrid rice), its parents 9311, Pei' ai 64S and Shanyou 63 (three-line hybrid rice combination) by the isotopic labeling and other techniques. The results showed that the mean of the Pn of the flag leaf sheathes for Liangyoupeijiu was 0.10 μmol CO2 m^-2 s^- 1 higher than that for Shanyou 63, and it was significantly higher at the third sta...