Abstract
C4 plants require a high capacity for RuBP-regeneration to maintain the balance to the high rates of carbon assimilation because of the CO2 concentrating pathway. However, the mechanisms for high RuBP-regeneration capacity are not clear. We analyzed the rate-limiting factors for RuBP-regeneration in maize compared with rice. CO2-saturated photosynthesis in maize was higher that in rice. This means that maize has high RuBP-regeneration capacity. Soluble protein-N was lower and insoluble-N was higher in maize than in rice. Although Rubisco specific activity in maize was significantly higher than that in rice, its total activity was lower. NADP-G3PDH, PGA kinase, cpFBPase activities, and the SPS Vmax activity and its Km value were all higher in maize. Furthermore, Chl, Cyt f and CF1 contents in maize were also higher than those in rice. From these results, we will discuss the mechanisms for higher RuBP-regeneration capacity in maize.
