Oxygen evolution and photosynthetic energy storage during the cell cycle of green alga Scenedesmus armatus characterized by photoacoustic spectroscopy

The photosynthetic activity of Scenedesmus armatus, synchronized by light/d ark regime of 14/10 hours, was characterized using the photoacoustic (PA) s pectroscopy technique. Frequency-dependent analysis of the PA signal was ca rried out to separate its photobaric and photothermal components. The photo chemical energy storage (ES) measured at a high frequency of 180Hz and the efficiency of oxygen evolution measured at a low frequency of 4Hz were foun d to have different runs during the light phase (14h) of the cell cycle. ES changed from 27% for young autospores illuminated for 0.5h to 35% for moth er cells starting to release the next generation of autospores. The efficie ncy of oxygen evolution rapidly increased, reaching the maximum value in 3- 4h, and next gradually declined with time during the cell cycle. The time o f the photothermal component of the PA signal creation measured in a PA cel l changed from 1.63 to 1.87ms. The coefficient of oxygen diffusion through the cell wall was 7.84 . 10(-7)cm(2)s(-1). In view of a very good correlati on between the PT signal and the cell volume during the cell cycle, the PA technique can also be employed to monitor the growth of cells or biomass pr oduction.