Abstract
We analyzed the responses of cyclic electron flow around PSI (CEF-PSI) to the light environments, using a model plant Arabidopsis thaliana. After the plants were grown under low-light conditions (LL) for 3-weeks, they were transferred to high-light conditions (HL). Both photosynthetic linear electron flow (LEF) and the electron flux in PSI were evaluated from both the quantum yields of PSII (QY(PSII)) and PSI (QY(PSI)), respectively. The activity of CEF-PSI was estimated as QY(PSI) - QY(PSI). After the transition from LL to HL conditions (24, 48, 96 h), these above parameters were measured. On the transitions, Fv/Fm decreased from 0.82 to 0.78. Chl fluorescence parameters, both qL and NPQ, increased. [P700+]/[P700]total also increased. Further, the activity of CEF-PSI increased. The values of both qL and [P700+]/[P700]total also increased. Thse results inidicated that the redox level of PQ regulated the activity of CEF-PSI.
