Controlling role of foliar nitrogen allocation strategy on the CO2 fertilization effect: using rice as an example

Elevated CO 2 generally increases the photosynthetic rate of rice, yet with a tendency for decreased foliar nitrogen (N) concentration at elevated CO 2 . The evidence for how photosynthetic N partitioning affect the response of rice to elevated CO 2 , however, is still limited. Here in this study, based on the two-years field experiments conducted at free-air CO 2 enrichment (FACE) system and the open-top chambers (OTC), along with a pot experiment with a variety of rice cultivars and the evidence from a global meta-analysis, we aim to investigate the relationship between foliar N allocation strategy and the CO 2 fertilization effect (CFE) of rice. We found that the CFE of rice were highly correlated with the foliar N allocation strategy. The photosynthetic N allocation to both the carboxylation system ( PNcb ) and the electron transport system ( PNet ) is strongly positively correlated with CFE, with an R 2 of 0.65 for both. This finding is also supported by the results from structural equation model, which further indicates that these two factors jointly determine the CFE of rice. We then able to generate a robust model to predict the CFE of rice on the basis of PNcb and PNet , which showed a 73% confidence level for the global meta-data across 56 experimental sites. Furthermore, this model was also robust and valid for various field N application rates. Our findings thus indicate that the foliar N allocation strategy has a controlling role on regulating the CFE of rice. This study offers a new perspective on understanding rice’s response to climate change and also will be beneficial for accurately projecting global crop yield in the context of future climate change.