Improving photosynthetic efficiency is a major target for increasing crop biomass production and yield potential. The canopy photosynthetic efficiency, which is determined by leaf area index, canopy architecture, and leaf photosynthetic properties, plays an important role in determining biomass accumulation. Perhaps because there has been an overemphasis on the photosynthetic properties of leaves rather than canopies, little progress has been made in increasing yield by enhancing photosynthetic efficiency. With the goal of improving rice (Oryza sativa) light use efficiency and identifying leaf photosynthetic parameters that are highly correlated with biomass accumulation, Qu et al. () systematically investigated 14 photosynthetic parameters and four morphological traits in over 200 accessions grown in two locales. Although there were large variations in photosynthetic parameters measured in different environments, they observed that photosynthetic rate under low light was highly related to biomass accumulation and also exhibited high genomic inheritability in both environments, suggesting its great potential to be used as a target for future rice breeding programs.