Abstract
We previously reported that water-water cycle (WWC) functions as a starter of photosynthesis (Makino et al. 2002). However, since CO2 assimilation was induced in the absence of O2, WWC was not essential as the photosynthetic starter. In 0% O2, the photosynthetic induction and the formation of NPQ was slow. Therefore, it is suggested that WWC rapidly produces ΔpH across thylakoid membranes, and produces ATP to activate Rubisco activase, then photosynthesis is induced. However, the activation of Rubisco did not limit photosynthesis during the induction phase. Because Rubisco activation already reached about 80% when the early phase of the photosynthetic induction. Rice belongs to a species with extensive dark inhibition of Rubisco. However, a rapid activation of Rubisco is also obsereved for the dark-treated rice leaves. Thus, the activation of Rubisco does not limit photosynthesis even in a species with dark inhibition of Rubisco.
