Modeling acclimation of leaf photosynthesis to atmospheric CO2 enrichment

In this study, we developed and analyzed a new model for the simulation of photosynthetic active nitrogen ( N P ) turnover dynamics in crops and assessed its impact on the acclimation of canopy photosynthesis to atmospheric CO 2 enrichment. Typical canopy models assume a vertical exponential decline of light interception following the Beer–Lambert law and vertical distributions of leaf N P contents directly proportional to the light distribution. This assumption is often inconsistent with experimental observations. We therefore modified and extended the photosynthesis model of the GECROS crop model to consider the trade-off that occurs between the use of degraded N P for plant growth and the synthesis of new N P . This model extension thus enabled the examination of the CO 2 -induced down-regulation of photosynthesis hypothesis using a crop model. The simulation results of the original and modified GECROS model were compared and evaluated based upon measurements of field-grown spring wheat. The modified GECROS model better simulated the dynamics of crop growth under varying atmospheric CO 2 concentrations. Furthermore, the application of different temperature functions to N P degradation strongly influenced the simulation results, revealing the necessity for improving the understanding of the temperature dependence of N P turnover for different crop species and varieties. In conclusion, the redistribution of nitrogen within the plant and its alternative use either for growth or the optimization of the photosynthetic apparatus is an important mechanism for crop growth acclimation to regionally changing climatic conditions and in particular, atmospheric CO 2 enrichment.