Assimilation – nitrogen content in leaf response

The response function for nitrogen content relative to carbon in the leaf on assimilation (radiation use efficiency approach). A response of zero, i.e. at CN ratios above p_QCN,Th , leads to a maximum reduction of photosynthesis, whereas if the response function is one, i.e. below p_QCN,Opt , there is no reduction of assimilation due to the carbon nitrogen ratio.