Evaluating differential effect of deltamethrin and carbofuran on growth characteristics of Westiellopsis prolifica Janet, a dominant nitrogen fixing cyanobacterium of tropical rice field ecosystem

Abstract

Recent trends of indiscriminate use of synthetic pesticides in different tropical rice fields has been affecting the soil flora and fauna including the most beneficial nitrogen fixing cyanobacteria . As nitrogen fixing cyanobacteria play an important role in soil fertility and acts as a natural bio fertilizer, the present study was carried out to investigate the differential effects of deltamethrin and carbofuran on Westiellopsis prolifica , an abundantly grown nitrogen fixing cyanobacterium in the rice fields of tropics. The study was conducted considering its dry biomass, protein, carbohydrate along with chlorophyll-a, and carotenoid content in a time- and dose-dependent exposure for 16 days. The resultant effect of both the pesticides was found to be pleiotropic for different concentrations of deltamethrin (25–75ppm) and carbofuran (20–60ppm). Results revealed that the growth parameters were more affected with carbofuran treatment than that of deltamethrin at their highest treated concentrations. Carbohydrate showed a gradual increase with carbofuran in a time and dose dependent manner whereas deltamethrin enhanced carbohydrate content up to 16th day from the day of inoculation only at 25ppm. Carotenoid showed a little but insignificant increase at the initial concentrations of both the pesticides whereas protein showed positive enhancement up to 4th day of inoculation when treated with deltamethrin. Though low concentrations stimulated some of the growth characteristics of the test organism, higher concentrations of both the pesticides were observed to be detrimental.