The study of fluorescence characteristics and biochemical composition of a marine diatom Thalassiosira pseudonana 3H in light and dark cycles-Ⅱ. The effects of light

The effects of light on the fluorescence characteristics and biochemical composition of a marine diatom Tha-lassiosira pseudonana in light and dark cycles were investigated with semi-continuous culture.The results indicate that, with the increase of growing light intensity, DCMU enhanced fluorescence yield (Fd/Chl), enhanced fluorescence ratio (Fd/F), cellular carbohydrate content.carbohydrate/chlorophyll a and carbohydrate/protein ratio increased, but the fluorescence yield and cellular chlorophyll a content decreased; The protein content declined with the increase of light intensity in the range of 10-100 μmol/(m²·s) and increased at higher than 100 μmol/(m²·s).Sampling time during the day had great effect on the relationships between growing light intensity and cellular chlorophyll a, carbohydrate content, carbohydrate/chlorophyll a and carbohydrate/protein ratio.