Effect of pesticides on cyanobacteria used in paddy cultivation

Abstract

Cyanobacteria or Blue Green Algae are ecologically important group of organisms since some forms are capable of fixing atmospheric nitrogen. In present studies effect of different herbicides (pretilachlor and butachlor) and insecticides (monocrotophos and chlorpyrifos) on physiological activity of Anabaena variabilis and Desmonostoc was analyzed. Tolerance limit, biomass, carbohydrate content, nitrate reductase activity and heterocyst frequency was analyzed in presence of different concentration of pesticides. Lower concentration (0.5 ppm) of pretilachlor and butachlor stimulates the growth of Anabaena variabilis and at high concentration (8 ppm) growth was inhibited. In case of chlorpyrifos and monocrotophos, both at low concentration i.e. 0.5 ppm and at higher concentration i.e. 8 ppm the cyanobacterial strain Anabaena variabilis there was no inhibition in growth. Desmonostoc have no significant effect on the growth in presence of herbicides where as showed positive growth in 8ppm of monocrotophos and chlorpyrifos. Desmonostoc sp. is able to tolerate higher concentration of herbicides (butachlor and pretilachlor) and insecticides (monocrotophos and chlorpyrifos) as compared to Anabaena variabilis. Since at low concentration of insecticides the physiological process of organism was not adversely affected, the organism can be used in biofertilizer technology program for insecticides (monocrotophos and chloropyrifos) and herbicides (butachlor and pretilachlor) applied fields.