Molecular Biology and Agriculture Division, Bhabha Atomic Research Centre, Bombay 400 085, India
* Corresponding author.
1Present address: National Botanical Research Institute, Rana Pratap Marg, Lucknow 226 001.
The non-heterocystous filamentous cyanobacterium Plectonema boryanum UTEX 594 grew rapidly microaerobically under nitrogen-starvation conditions in continuous high light Intensity by conducting oxygenic photosynthesis and oxygen sensitive nitrogen-fixation in alternating cycles. During diazotrophic phase, the light harvesting pigment phycocyanin declined with a concomitant depression In light dependent oxygen evolution by the cyanobacterium. A substantial component of light dependent carbon dioxide fixation during diazotrophic phase was not Inhibited by DCMU in spite of complete cessation of photosynthetic oxygen evolution. Endogenous-reductant dependent electron transfer to photosystem I during diazotrophic phase Is postulated even during photoautotrophic growth.
cyanobacteria, nitrogen fixation, photosynthesis, DCMU resistance, endogenous reductant
