Antagonism at combined effects of chemical fertilizers and carbamate insecticides on the rice-field N₂-fixing cyanobacterium Cylindrospermum sp. in vitro

Abstract

Effects of chemical fertilizers (urea, super phosphate and potash) on toxicities of two carbamate insecticides, carbaryl and carbofuran, individually to the N2-fixing cyanobacterium, Cylindrospermum sp. were studied in vitro at partially lethal levels (below highest permissive concentrations) of each insecticide. The average number of vegetative cells between two polar heterocysts was 16.3 in control cultures, while the mean value of filament length increased in the presence of chemical fertilizers, individually. Urea at the 10 ppm level was growth stimulatory and at the 50 ppm level it was growth inhibitory in control cultures, while at 100 ppm it was antagonistic, i.e. toxicity-enhancing along with carbaryl, individually to the cyanobacterium, antagonism was recorded. Urea at 50 ppm had toxicity reducing effect with carbaryl or carbofuran. At 100 and 250 ppm carbofuran levels, 50 ppm urea only had a progressive growth enhancing effect, which was marked well at 250 ppm carbofuran level, a situation of synergism. Super phosphate at the 10 ppm level only was growth promoting in control cultures, but it was antagonistic at its higher levels (50 and 100 ppm) along with both insecticides, individually. Potash (100, 200, 300 and 400 ppm) reduced toxicity due to carbaryl 20 and carbofuran 250 ppm levels, but potash was antagonistic at the other insecticide levels. The data clearly showed that the chemical fertilizers used were antagonistic with both the insecticides during toxicity to Cylindrospermum sp.

Probit Analysis of Carbamate-Pesticide-Toxicity at Soil-Water Interface to N2-Fixing Cyanobacterium Cylindrospermum sp

“…It forms a suspension of hand-shaken batch liquid cultures. Growth conditions of the cyanobacterium with liquid and agar Chu-10 medium under the N 2 -fixing condition (C-N medium) and the same with calcium nitrate supplementation (C+ N medium) were detailed elsewhere (Padhy et al, 2014). Insecticides, carbaryl and carbofuran as well as fungicides, ziram, zineb and mancozeb, were used.…”

“…In flooded rice soil particularly, the growth of photosynthetic N 2 -fixing cyanobacteria (blue-green algae) along with the crop causes the addition of nitrogenous compounds and ultimately helps the soil-binding process by cell-death. These soil microbes get affected by pesticides used for rice (Panigrahi et al, 2003;Padhy et al, 2014).…”

Exogenous Phytohormones Modulates Cypermethrin Stress in Anabaena sp. and Nostoc Muscorum: Toxicity Alleviation by Up-regulation of Ascorbate-glutathione Cycle

“…Cyanobacteria are essential constituents of the fresh water ecosystem and paddy eld soil where moist and nutrient rich environment regulate their growth, physiology, abundance and habitat selection 19,20 . The indirect effect of pesticide also recorded on cyanobacteria by notifying the oxidative stress caused by overproduction of free radical 17,21,22 .…”