Up-regulation of cyclic electron flow and down-regulation of linear electron flow in antisense-rca mutant rice

Abstract

To investigate how excess excitation energy is dissipated in a ribulose-1,5-bisphospate carboxylase/oxygenase activase antisense transgenic rice with net photosynthetic rate (P N) half of that of wild type parent, we measured the response curve of P N to intercellular CO2 concentration (C i), electron transport rate (ETR), quantum yield of open photosystem 2 (PS2) reaction centres under irradiation (Fv′/Fm′), efficiency of total PS2 centres (ΦPS2), photochemical (qP) and non-photochemical quenching (NPQ), post-irradiation transient increase in chlorophyll (Chl) fluorescence (PITICF), and P700+ re-reduction. Carboxylation efficiency dependence on C i, ETR at saturation irradiance, and Fv′/Fm′, ΦPS2, and q P under the irradiation were significantly lower in the mutant. However, NPQ, energy-dependent quenching (qE), PITICF, and P700 + re-reduction were significantly higher in the mutant. Hence the mutant down-regulates linear ETR and stimulates cyclic electron flow around PS1, which may generate the ΔpH to support NPQ and qE for dissipation of excess excitation energy. © 2008 Springer Science+Business Media B.V.