Abstract: In order to study the rate of leaf appearance on main stem of rice,the experiments were conducted with 3 varieties and 8 sowing dates. The results showed that leaf number on main stem was closely related to the days to heading. Equations for different varieties were derived by fitting relation of the number of leaf on main stem to effective temperature sum. There was the different rate of leaf appearance among leaf positions on main stem.

Key words: coal, mining area, ecological vulnerability, index system, Shengli Coalfield.