Effect of free-air atmospheric CO2 enrichment on dark respiration of rice plants (Oryza sativa L.)

Elevated carbon dioxide (CO2) has been shown to have variable effects on plant respiration rates in publications. However, there is little measurement of dark respiration rate of rice plant (Oryza sativa L.) conducted in free-air CO2 enrichment (FACE). In this study, seasonal variation in the effect of elevated CO2 on dark respiration of aboveground rice was investigated by FACE experiments in Wuxi city, Jiangsu province of China. The results showed that increasing the present atmospheric CO2 concentration by 200 μmol mol−1 did not significantly affect the specific dark respiration coefficient (Rdw25) of aboveground rice plants expressed on the basis of dry weight biomass throughout the growth season, which may be attributed to no significant effect of the elevated CO2 on the nitrogen content in aboveground rice plants. However, the canopy dark respiration coefficient (Rd25) of aboveground rice plants expressed on the basis of ground area was periodically stimulated by the elevated CO2 by about 17% as the elevated CO2 significantly increased aboveground rice biomass over the entire rice season. This study indicates that free-air atmospheric CO2 enrichment did not significantly affect the specific respiration coefficient of aboveground rice plants while it significantly stimulated the canopy respiration coefficient.