Four rice combinations were used to study the relationship between distribution of 14^C photosynthesis production of flag leaf of main crop and yield of ratooning rice. The results indicated that:(1) About 70%-75% 14^C photosynthesis production of flag leaf of main crop was distributed in spikes, and about 25%-30% remained in flag leaves and pedicle sheathes. (2) About 65%-80% photosynthesis production of flag leaf was distributed mainly in the upper second and third internodes of main crop. (3) Distribution proportion of photosynthesis ...