Photoinhibition of photosynthesis and growth responses at different light levels in psbA gene mutants of the cyanobacterium Synechococcus (original) (raw)

1991, Physiologia Plantarum

of photosynthesis and growth responses at different light levels in psbA gene mutants of the cyanobacterium Synechococcus.-Physioi. Plant. 82: 1-8. Photoinhibition of photosynthesis and growth responses at different light levels (iO, 120 and 250 [imol m-s"') were studied in psbA gene mutants R2S2C3 {psbAI gene present) and R2K1 (psbAUipsbAlIl genes present) of the cyanobacterium Synechococcus sp. PCC 7942 {Anacystis nidulans R2). Mutant R2K1 (possessing form II of the D1 protein of photosystem II) was much more resistant to photoinhibition than the mutant R2S2C3 (possessing form 1 of the Dl protein). At moderate inhibitory light levels (100 to 300 [xmol m-s"') this was largely ascribed to an increased resistance of the photosystem II reaction centres possessing form II of the Dl protein. However, at higher light levels the higher resistance of mutant R2K1 was assigned to a higher rate of photosystem II repair, i.e. turnover of the Di protein. Moreover, our results support the hypothesis that photoinhibition of photosystem I] and photoinhibitory induced quenching are due to separate processes. Results from growth experiments show that the R2K1 mutant has a slower growth rate than the R2S2C3 mntant but shows an increased survival under high light stress conditions. It is hypothesized that high resistance to photoinhibition, though allowing a better survival under high light, is not advantageous for optimal growth.