The study looked at different types of rice leaves to see how their chlorophyll content affects grain yield. They found that the chlorophyll content in certain leaves during the mid-to-late rice growth stages is closely related to grain weight per plant. Specifically, slower chlorophyll degradation in the flag leaf and top second leaf led to higher grain yield. This suggests that selecting rice plants with slower chlorophyll degradation in these leaves could help improve grain yield in hybrid rice.