Effects of the Herbicide Molinate on Mixotrophic Growth, Photosynthetic Pigments, and Protein Content ofAnabaena sphaericaunder Different Light Conditions

The effects of the carbamate herbicide molinate on growth and chlorophyll a, biliprotein, and protein content of the nitrogen-fixing cyanobacteriumAnabaena sphaericagrown mixotrophically under 3000- and 300-lux light intensity were studied. Under two light intensities, the three concentrations of molinate tested (5, 25, and 50 μg ml−1) can significantly inhibit algal growth in a dose-dependent manner. The high concentration of molinate (50 μg ml−1) stimulated the synthesis of chlorophyll a and protein, but inhibited the formation of biliprotein, and these effects appear to be greater at 3000 lux than at 300 lux. The effects of the other two concentrations of molinate (5 and 25 μg ml−1) on chlorophyll a and biliprotein varied with time, but 5 μg ml−1molinate had an inhibitory effect on the synthesis of protein. It was demonstrated that different concentrations of molinate had different effects on chlorophyll a, biliprotein, and protein content, which varied with light intensity. The results support the suggestion that the physiological mode of molinate toxicity toA. sphaericais related to its interference with the metabolism of protein, particularly the formation and functional effectiveness of some special protein.