In vivo regulation of electron and proton transport under different environmental conditions

Description: Nowadays, it is considered that improvements in the photosynthetic rates of individual leaves within the canopy may be the solution to increase crop yields for the growing population in the coming decades. In that logic, it is of great importance to understand the operation, regulation, and limitations of photosynthesis under different environments. To contribute with this objective, the regulation of electron and proton fluxes produced in the thylakoid discs under increasing irradiance, decreasing CO2 concentrations and decreasing temperatures was studied in the Solanacea species Juanulloa aurantiaca through the use of non-invasive biophysical techniques (chlorophyll fluorescence and absorbance changes at 520 and 820 nm) in vivo. The results showed that the mechanisms that regulate the flux of electrons and protons when the metabolism in the stroma is reduced by decreasing CO2 concentrations or decreasing temperatures works in the same way. The flux of electrons generated a proton motive force (pmf) that decreased the pH in the lumen, thereby decreasing the rate of oxidation of plastoquinol (ke) and increasing the non-photochemical quenching (NPQ). A decrease of ke was accompanied by a decrease of the conductivity of ATP synthase to protons (gH+). Leaves exposed to increasing irradiance showed lower pmf values and a relatively non-altered ke and gH+.

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