Reduced nitrogen allocation to expanding leaf blades suppresses ribulose-1,5-bisphosphate carboxylase/oxygenase synthesis and leads to photosynthetic acclimation to elevated CO2 in rice

Net photosynthetic rate (P-N) measured at elevated CO2 concentration (C-e), ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), and nitrogen (N) content in rice leaves decreased significantly after exposure to long term C-e. The reduction in P-N, Rubisco, and leaf N at C-e was similar for the last fully expanded leaf blade (LFELB) and expanding leaf blade (ELB). Spatial leaf N content in the ELB was highest in the zone of cell division, sharply declined as cell expansion progressed and gradually increased with cell maturation. Maximum reduction in spatial leaf N and Rubisco content was found at C-e only within cell expansion and maturation zones. The spatial leaf N content correlated well with the amount of Rubisco synthesized during leaf expansion, suggesting that N deposition into the expanding leaf blade may be the key for Rubisco synthesis and possibly photosynthetic acclimation to C-e.