Decreased wheat grain yield stimulation by free air CO2 enrichment under N deficiency is strongly related to decreased radiation use efficiency enhancement

The present study demonstrates that yield stimulation by e[CO2] is smaller under severe N deficiency compared to high N supply in wheat. In contrast to the results of another FACE study, this decrease was not due to reduced AR but reduced RUE, which might be attributed to both restrictions on source activity, i.e. photosynthetic capacity and sink size, i.e. ear growth.