大气CO2对C3植物光合电子传递速率与净光合速率之比的影响

he ratio of linear electron transport to assimilation (ETR/A) has been used to determine whether the plant is under optimal conditions or if ETR is accurately estimated. However, how ETR/A responds to short- and long-term variations in CO2 is still uncertain. Here, we conducted a controlled experiment to explore the short-term CO2 response of ETR/A in sunflower and cowpea. And we compiled published data to study the effect of long-term elevated growth CO2 on ETR/A in different plant functional groups. Our experiment showed that ETR, photochemical efficiency of photosystem II, and photochemical quenching increase while ETR/A decreases with increasing CO2. The CO2 sensitivity of ETR and ETR/A at low [CO2] (Rubisco-limiting condition) is much higher than that at moderate to high [CO2] (electron transport-limiting stage). Our compiled data showed significant effects of plant functional group and long-term CO2 treatments on ETR/A, indicating that current empirical ETR/A threshold values are not universally applicable for all species at different atmospheric conditions. Long-term elevated CO2 increased A but did not affect ETR, which reduced ETR/A by 21% when compared with the ambient CO2. Our results indicate an imbalance between electron transport and carboxylation under elevated CO2, limiting leaf photosynthesis under future CO2 concentrations.