Taking the heterotic combinations which respectively had moderately-rolled leaves and flat leaves at middle and later stages as tested materials, the biological effects in the heterotic combination of the moderately-roiling leaf mutant RL（f） were studied. The results showed that （i） there was insignificant difference between the leaf morphological characteristics of the RL（t） and fiat leaf heterotic ombinations at early growth stage in that beth of them had fiat leaves and relatively big basic leaf angles; （it） the stomatal conductance, the intercellular CO2 concentration, transpira- tion rate and photosynthetic rate of the three top leaves of the RL（t） heterotic com- bination were significantly higher than those of the flat leaf heterotic combination at middle and later stages, which laid the foundation for increasing the yield per unit area; （iii） the light transmittance of the RL（f） heterotic combination in population at the middle part was higher than that of flat leaf heterotic combination, resulted in improved light interception condition at middle and lower parts of the population and increased the utilization efficiency of tight energy; and （iv） this research revealed that the RL（t） heterotic combination could not only maintain a larger amount of the effective panicles but also could present large-panicle characteristic, especially in high-density condition, and also the ability of adjusting yield components the RL（f） heterotic combination was significantly increased under different densities. This study would provide a theoretical basis for the principle of high-yielding breeding with the application of the moderately-rolling leaf mutant in rice.
