Evaluation of toxicological impact of cartap hydrochloride on some physiological activities of a non-heterocystous cyanobacterium Leptolyngbya foveolarum

Abstract

The present study was aimed to the evaluation of toxicological impact of insecticide cartap hydrochloride on photosynthesis and nitrogen assimilation of a non-heterocystous cyanoprokaryote Leptolyngbya foveolarum isolated from paddy fields of Punjab, India. The microorganism tolerated commercial grade insecticide up to 80ppm. Lower concentration (20ppm) of cartap supported good growth with high dry weight of biomass, total protein content, photosynthetic pigments, photosynthesis and respiration compared to untreated control cultures while higher concentrations (40 and 60ppm) inhibited these parameters in a dose dependent manner. Treatment of the microorganism with 60ppm cartap lowered the content of photosynthetic pigments with maximum inhibitory effect on phycoerythrin (70% decrease) followed by allophycocyanin (66% decrease). Rates of photosynthesis and respiration were inhibited by 63% and 45%, respectively, while PS-I, II and whole chain activity were decreased by 45%, 67% and 40% respectively, compared to untreated control cultures. Cartap at 60ppm decreased nitrate and nitrite uptake by 31% and 61%, respectively, whereas uptake of ammonium was slightly increased (18%) in cartap (60ppm) treated cells. Nitrate and nitrite reductase, and glutamine synthetase activities of the microorganism decreased by 36–50% in 60ppm cartap. The low levels of growth, photosynthetic pigments and activities of nitrogen assimilating enzymes in cells grown in nitrogen depleted medium supplement with insecticide indicated that insecticide may be used by the organism as a nitrogen source.