Effect of CO2 content in air on functioning of Arabidopsis thaliana photosynthetic electron transport chain.

The functioning of the photosynthetic electron transport chain and the proceeding of accompanying processes were studied in Arabidopsis thaliana plants acclimated during 2weeks to reduced (150ppm) or elevated (1000ppm) CO2 concentrations in air. Measured at ambient CO2 , the quantum yields of both photosystems were lower in plants acclimated to these CO2 concentrations as compared with control plants grown at ambient CO2 . The difference was more pronounced at the beginning of the illumination. It is discussed that this difference resulted from the difference in Rubisco content, which at both reduced and elevated CO2 in air was lower than in control plants. The quantum yield of regulated non-photochemical energy loss in photosystem II under both reduced and elevated CO2 was lower than in control plants. This correlated with reduced expression of the PsbS protein gene. H2 O2 content in the leaves increased during the first days of plant adaptation to 150ppm CO2 , but then decreased. The increase resulted from enhanced rates of both photorespiration and Mehler reaction, while the following decrease resulted from enhancing contents of ascorbate peroxidases in all cell compartments.