2.6. Measurement of whole cell O2 evolution and
respiration
The rate of photosynthesis in treated and untreated cells ofAnabaena PCC 7120 were measured in terms of photosynthetic oxygen
evolution using Clark type O2 electrode (Digital oxygen
system model-10, Rank Brothers, U.K). After 72 h of growth,
cyanobacterial cells were harvested and the cell suspension were
illuminated under the saturating light intensity of 360 μmol photons
m−2 s−1 PAR in a temperature
controlled air tight reaction vessel, at 25 °C for 3 min. Respiration
rate was measured in the darkness with the help of same instrument in
terms of O2 consumption. Photosynthetic oxygen evolution
rate was expressed as μmol O2 evolved
(mg–1 Chl a ) h–1 and
respiratory rate was expressed as μmol O2 consumed
(mg–1 Chl a ) h–1.