Influence of Co2 Concentrating Mechanism on Photoinhibition in Synechococcus sp. PCC7942 (Cyanophyceae)

Abstract In this study the effects of inorganic carbon transport in the cyanobacterium Synechococcus sp. PCC7942 on its photoinhibition were investigated. The photosynthetic oxygen evolution of samples under a strong irradiance treatment at 100 µM KHCO3 was much higher than that at 10,000 µM KHCO3. After strong irradiance treatment, the abundance of the sbtA transcript encoding a Na+-dependent transporter was significantly higher under treatment at 100 µM KHCO3 than at 10,000 µM KHCO3. Lincomycin had little effect on the difference of photosystem II (PSII) activity decline under these two treatments, which suggests that CCM activity reduces photodamage but does not boost the rate of PSII repair. The maximal photosynthetic efficiency was decreased significantly during the strong irradiance treatment, and its decrease was enhanced when the external DIC concentration was raised from 100 to 10,000 µM KHCO3. The JIP test showed that there were more active reaction centres under low Ci conditions after high lig...