부산대학교 도서관

Changes in the in vivochlorophyll fluorescencequenching, photosynthesis and pigment composition werefollowed in the green alga Chlorococcumsp.during exposure of the culture to nitrogen deficiencyand salinity stress with the aims to study theinterrelations between changes in physiological andphotochemical parameters and xanthophyll-cyclepigments content during adaptation to stress, and toevaluate the capacity of this green alga to producesecondary carotenoids in tubular photobioreactors.Exposure of Chlorococcumto nitrogendeficiency, 0.2 M NaCl and high irradiance outdoorscaused a strong depression of the photosyntheticactivity and of photochemical quantum yield ofPSII (Fv/Fm). These changes wereaccompanied by an increase of the non-photochemicalquenching coefficient (NPQ), of the amount ofxanthophyll-cycle pigments and of thecarotenoid/chlorophyll ratio. As a result of exposureto stress conditions, cell division completelystopped, although an increase in the biomass dryweight could be detected due to an increase in thecell size. These processes were followed, with acertain delay (15–20 h), by massive appearance ofsecondary carotenoids that reached the maximum (about50% total carotenoids) after 2–3 days of cultivation.The results show that despite of the lower carotenoidcontent (2 mg g-1dry wt) as compared with Haematococcus, Chlorococcumcan be apotentially interesting strain for secondarycarotenoid production because of its higher growthrate.