NOVEL AMPLIFICATION OF NONPHOTOCHEMICAL CHLOROPHYLL FLUORESCENCE QUENCHING FOLLOWING VIRAL-INFECTION IN CHLORELLA

In higher plants non-photochemical dissipation of excess light, trappe d by the pigment pool of photosystem II, prevents photodamage to the p hotosynthetic apparatus, We report here that an algal virus infecting Chlorella strain Pbi induces non-photochemical quenching of photosyste m II fluorescence, indicating enhanced loss of absorbed light energy f rom photosystem II, This phenomenon occurs soon after the establishmen t of the virus infection cycle and is observed at low irradiance (20 m u mol quanta m(-2) s(-1)). At low light, infection associated non-phot ochemical quenching is not linked to extensive conversion of violaxant hin to antheraxanthin and zeaxanthin, However, such conversion occurs rapidly (2-10 min) in infected cells under conditions of high irradian ce (100-300 mu mol quanta m(-2) s(-1)). Under similar conditions uninf ected Chlorella cells do not display significant changes in nonphotoch emical quenching.