EFFECT OF SULFUR-DIOXIDE ON ALGAE

Photosynthetic activity in soil of ph 7. 1 was unaffected by a 10-day exposure to 0. 5 ppm sulfur dioxide (SO//2) in air. However, the photosynthetic activity of Anabaena flos-aquae and Chlamydomonas reinhardtii suspended in a thin layer of medium at an initial pH of 6. 0 was almost totally inhibited within 24 hours by treatment with 1. 0 ppm SO//2 in air. The pH of the medium decreased to 5. 2 or below during this period. If the decrease in pH was prevented by the addition of soil or phosphate buffer, no inhibition of photosynthesis was observed. In contrast, addition of an acidic soil to a medium of pH 4. 9 offered no protection from the adverse effects of SO//2. The data indicate that the decrease in pH of samples exposed to SO//2 was not the sole cause of the inhibition of photosynthetic activity.; Photosynthetic activity in soil of pH 7.1 was unaffected by a 10-day exposure to 0.5 ppm sulfur dioxide (SO2) in air. However, the photosynthetic activity of Anabaena flos-aquae and Chlamydomonas reinhardtii suspended in a thin layer of medium at an initial pH of 6.0 was almost totally inhibited within 24 hours by treatment with 1.0 ppm SO2 in air. The pH of the medium decreased to 5.2 or below during this period. If the decrease in pH was prevented by the addition of soil or phosphate buffer, no inhibition of photosynthesis was observed. In contrast, addition of an acidic soil to a medium of pH 4.9 offered no protection from the adverse effects of SO2. The data indicate that the decrease in pH of samples exposed to SO2 was not the sole cause of the inhibition of photosynthetic activity.