Differences between maize and rice in N-use efficiency for photosynthesis and protein allocation

The N-use efficiency for photosynthesis was higher in a C-4 Plant, maize, than in a C-3 plant, rice, including rbcS antisense rice with optimal ribulose-1,5-bisphosphate carboxylase (Rubisco) content for CO2-saturated photosynthesis, even when photosynthesis was measured under saturating CO2 conditions. The N cost for the C-4 cycle enzymes in maize was not large, and the lower amount of Rubisco allowed a greater N investment in the thylakoid components. This greater content of the thylakoid components as well as the CO2 concentrating mechanism may support higher N-use efficiency for photosynthesis in maize.