Perspectives of improving rice photosynthesis for higher grain yield

Many efforts have been made to enhance rice photosynthesis for higher grain yields, although such knowledge has seldom been integrated into rice breeding programs. In this review, I first address the limitations and challenges of the theory that yield is controlled by photosynthesis, a concept rooted in the fact that carbon forms a significant part of plant mass, with photosynthesis acting as the fundamental pathway for carbon assimilation. Subsequently, the discussion covers photosynthesis indices, their measurement techniques, and the challenges in establishing correlations between photosynthesis indices and yields. The review then delves into recent advancements, including leveraging natural variations, enhancing the electron transport chain, augmenting the efficiency of ribulose bisphosphate carboxylase/oxygenase (Rubisco), increasing CO2 concentration around Rubisco, initiatives like the C4 rice project, strategies for photorespiration bypass, and non-leaf photosynthesis contributions. The conclusion emphasizes future research directions such as advocating for the incorporation of photosynthesis within broader organismic processes, unraveling the complex link between photosynthesis and grain yield, developing efficient and direct methods for photosynthesis phenotyping, and assessing photosynthetic performance under actual field conditions.