Estimating microbial respiratory CO2 from endophytic bacteria in rice.

Endophytes are symbiotic microbes that live inside host plants. These endophytic symbionts receive photosynthesized carbohydrates from host plants while conferring symbiotic benefits to their host. During photosynthate-fueled respiration, endophytes release CO2 into the intercellular spaces of their host plants in which they reside. We evaluated the possibility for host plants' re-assimilation of microbial respiratory CO2. In planta and in vitro assays were conducted to examine respiratory characteristics of endophyte-symbiotic plants. Endophyte-inoculated plants had a greater in planta respiration rate. In vitro data demonstrated that respiration rates of endophytes are dependent on the total amount of endophytes and the concentration of carbohydrate supply. Assuming the host plant offers sufficient carbohydrates, we estimate that CO2 produced during microbial respiration in planta accounts for about 57% of the CO2 assimilated by the photosynthetic pathways of the symbiotic plant. This suggests that endophytes can produce significant amounts of CO2, which could then be re-assimilated by host plants.