Photostimulation of production in the green alga Chlamydomonas reinhardtii upon photoinhibition of its -evolving system

A brief exposure (15–30 min) of green alga Chlamydomonas reinhardtii cells to high-intensity light ( 2000 μ mol m - 2 s - 1 ) was accompanied by rapid suppression of photosynthetic O 2 evolution. The decline in the rate of O 2 evolution was followed by stimulation of H 2 production under light of 15 μ mol m - 2 s - 1 . The effect was dependent on light intensity and cell suspension density. It appears that photoinhibition of photosynthetic O 2 evolution led to anaerobiosis that is favorable for H 2 production.