Anisohydric characteristics of a rice genotype ‘ARC 11094’ contribute to increased photosynthetic carbon fixation under fluctuating light conditions

Photosynthetic induction, which is the response of the CO 2 assimilation rate to a stepwise increase in light intensity, potentially affects plant carbon gain and crop productivity in field environments. Although natural variations in photosynthetic induction are determined by CO 2 supply and its fixation, detailed factors, especially CO 2 supply, are unclear. This study investigated photosynthesis at steady and non-steady states in three rice ( Oryza sativa L.) genotypes: ARC 11094, Takanari, and Koshihikari. Stomatal traits and water relations in the plants were evaluated to characterise CO 2 supply. Photosynthetic induction was higher in ARC 11094 and Takanari than in Koshihikari owing to an efficient CO 2 supply. The CO 2 supply in Takanari is attributed to its high stomatal density, long guard cell length, and extensive root mass, whereas that in ARC 11094 is attributed to its high stomatal conductance per stoma and stomatal opening in leaves with insufficient water (i.e. anisohydric stomatal behaviour). Our results suggest that there are various mechanisms for realising an efficient CO 2 supply during the induction response. These characteristics can be useful for improving photosynthetic induction and, thus, crop productivity in field environments in future breeding programs.