MONITORING THE INFLUENCE OF CHEMICAL FERTILIZERS ON TOXICITY OF CARBAMATE FUNGICIDES TO THE RICE FIELD CYANOBACTERIUM CYLINDROSPERMUM SP.

摘要

The influence of chemical fertilizers, such as urea, super phosphate and potash, on the toxicities of carbamate fungicides, ziram, zineb and mancozeb to the nitrogen-fixing rice-field cyanobacterium Cylindrospermum sp. was individually monitored in vitro, partially lethal levels of each fungicide. The average number of vegetative cells between two polar heterocysts was 16.3 and the mean value of filament length was 47.8 ± 8.7 μm, in control cultures. Both average numbers of vegetative cells in filaments and mean values of filament length increased in the presence of chemical fertilizers. Urea at 10 and 50 ppm levels had toxic-ity-reducing effects of the fungicides used for the cyanobacterium. Super phosphate, at the 10 ppm level for ziram and at 10 and 50 ppm levels for zineb, had growth-enhancing (toxicity reducing) effects on the cyanobacterium. At 3 and 5 ppm levels of mancozeb, only the 10 ppm level of super phosphate reduced the toxicity. The level of 100 ppm potash only (but not any higher level) caused reductions in toxicity of the used fungicides to the cyanobacterium.