Abstract
Electron-transport components in maize are responsible for C4-cycle and RuBP-regeneration. We estimated the amounts of electron-transport components for RuBP-regeneration using isolated mesophyll cells (MC) and bundle-sheath cells (BS). Assuming (electron-transport component ratio for RuBP-regeneration to C4-cycle in MC)=(NADPH-consumption ratio by NADP-G3PDH and NADP-MDH in MC)=(NADP-G3PDH activity ratio in MC and BS), the amounts of electron-transport component for RuBP-regeneration can be estimated to be (electron-transport component in BS)+[(electron-transport component in MC)×(NADP-G3PDH activity ratio in MC)]. The ratios of NADP-G3PDH activity, CF1 and Cyt-f contents in MC and BS were 45:55, 44:56 and 58:42, respectively. Consequently, 76% of CF1 content and 68% of Cyt-f content may be for RuBP-regeneration. Examining CO2-saturated photosynthesis per unit of such electron-transport components for RuBP-regeneration, it was higher than in rice. The results suggested that higher RuBP-regneration capacity in maize was not simply explained by the amount of such electron-transport components, but was still more highly efficient.
