Updating the steady state model of C4 photosynthesis.

C4 plants play a key role in world agriculture. For example, C4 crops such as maize and sorghum are major contributors to both first and third world food production and the C4 grasses sugarcane, miscanthus and switchgrass are major plant sources of bioenergy. In the challenge to manipulate and enhance C4 photosynthesis, steady state models of leaf photosynthesis provide an important tool for gas exchange analysis and thought experiments that can explore photosynthetic pathway changes. Here the C4 photosynthetic model by von Caemmerer and Furbank (1999) has been updated with new kinetic parameterisation and temperature dependencies added. The parameterisation was derived from experiments on the C4 monocot, Setaria viridis, which for the first time provides a cohesive parametrisation. Mesophyll conductance and its temperature dependence have also been included, as this is an important step in the quantitative correlation between the initial slope of the CO2 response curve of CO2 assimilation and in vitro PEP carboxylase activity. Furthermore, the equations for chloroplast electron transport have been updated to include cyclic electron transport flow and equations have been added to calculate electron transport rate from measured CO2 assimilation rates.