Abstract: Based on the determination of dry matter and caloric value, this paper studied the characteristics of energy accumulation and the dynamics of caloric value in the yield-forming process of rice cultivars Shanyou 63 (three-line hybrid rice), Liangyou 2186 (two-line hybrid rice), and IR64 (conventional rice). The results showed that at fully grain-maturing stage, the amount of dry matter in Shanyou 63, Liangyou 2186 and IR64 was 1926.38 g·m^-2, 1933.80 g·m^-2 and 1842.30 g·m^-2, and that of accumulated energy was 31137.05 kJ·m^-2, 31060.63 kJ·m^-2 and 30454.89 kJ·m^-2, respectively, showing no significant difference among the cultivars. In the process of grain filling, the apparent transformation ratio of energy in Shanyou 63, Liangyou 2186 and IR64 was about 38.95%, 28.38% and 32.66%, respectively, implying that the energy flow in Shanyou 63 and IR 64 was smoother than that in Liangyou 2186, and the output of energy from stem to the sink of grain was blocked in Liangyou 2186. The ratio of energy partitioning to the sink of grain was 53.03%, 46.43% and 50.11% for Shanyou 63, Liangyou 2186 and IR64, respectively, showing the energy partitioning heterosis in three-line hybrid rice Shanyou 63. As for the caloric value, it had no significant difference among the three cultivars, but decreased in the order of leaf＞grain＞sheath＞stem＞root, ranging from 16.81～17.25 kJ·g^-1, 15.89～16.54 kJ·g^-1, 14.33～15.49 kJ·g^-1, 14.23～15.15 kJ·g^-1, and 11.51～13.25 kJ·g^-1, respectively. It was also shown that there was a significant positive correlation of caloric value with carbon content, chlorophyll a content, and nitrogen content in rice plant, with the determination coefficient R² being 0.609, 0.471 and 0.485, respectively.

Key words: Natural secondary forest, Forest species, Structure, Analytic hierarchy process