No Down-Regulation of Photosynthesis in the Offspring of Rice Grown Under Free-Air CO2 Enrichment (FACE)

Rising CO2 increases photosynthesis in C3 plants owing to the increase of its substrate concentration and inhibition of photorespiration. After long-term exposure to elevated CO2, however, the stimulatory effect decreases gradually in many C3 plants so that the net photosynthetic rate (P n) is lower than that in plants grown in ambient air when measured at the same CO2 concentration. This phenomenon, the so called down-regulation of photosynthesis, is often reported in CO2-enriched current generation plants. It has not been known whether the down-regulation is preserved or eliminated in the offspring from seeds of plants grown at elevated CO2. In Chinese free-air CO2 enrichment experiments the leaf Pn was significantly lower in CO2-enriched rice but not in the CO2-enriched rice offspring grown in ambient air when measured at comparable CO2 concentrations, indicating that no down-regulation of photosynthesis occurred in the offspring of CO2-enriched rice.