Increased atmospheric CO2 concentration causes modification of physiological, biochemical and histological characteristics that affects rice-Bipolaris oryzae interaction.

The leaf anatomy, photosynthetic system parameters and accumulation of carbohydrates were determined at different times for Bipolaris oryzae pathogenesis in two rice cultivars (BRS Querência and Inov CL), grown in an environment with 400 ppm or 700 ppm of atmospheric CO₂. The results demonstrated that the plants exposed to 700 ppm underwent changes in anatomical characteristics (reduction in parenchyma thickness and size of bulliform cells), photosynthetic parameters (increased carbon assimilation rate, leaf intercellular CO₂ concentration and water use efficiency, and reduction of stomatal conductance to water vapor, transpiration rate and carboxylation efficiency), and carbohydrate accumulation (increased concentration of soluble sugars and starch), when compared to plants at 400 ppm. Therefore, the changes in morphological traits of the leaf and the accumulation of carbohydrates, which were stimulated in the rice plants by increased CO₂ concentration (700 ppm), were associated with less severe brown spot, caused by B. oryzae. [ABSTRACT FROM AUTHOR]