Tea tree (Melaleuca alternifolia) canopy was sprayed with low concentration of NaHSO3 or mixture of NaHSO3+ KH2PO4. The treatments significantly enhanced net photosynthetic rate (PN), carboxylation efficiency (CE), and the maximum response of PN to intercellular CO2 concentration. The enhancement of PN by foliar application of low concentrations of bisulfite was due to increasing CE relevant to ribulose-1,5-bisphosphate (RuBP) carboxylase/oxygenase activity and regeneration rate of RuBP depending on ATP formation. and W.-J. Yang ... [et al.].
To investigate how excess excitation energy is dissipated in a ribulose-1,5-bisphospate carboxylase/oxygenase activase antisense transgenic rice with net photosynthetic rate (PN) half of that of wild type parent, we measured the response curve of PN to intercellular CO2 concentration (Ci), 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 Ci, ETR at saturation irradiance, and Fv'/Fm', ΦPS2, and qP 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. and S.-H. Jin ... [et al.].