EFFECT OF DIMETHOATE AND CHLORFENVINPHOS ON PLASMA-MEMBRANE INTEGRITYOF SYNECHOCYSTIS SP. PCC-6803

The organophosphorus (OP) insecticides dimethoate and chlorfenvinphos, at all selected concentrations (0-500 mu mol liter(-1)), reduced the rate of accumulation of uranine and enhanced fluorescence quenching of 9-amino-6-chloro-2-methoxyacridine (ACMA), There was a significant no nlinear negative correlation between insecticide concentrations and ur anine accumulation. The reduction in amount of uranine trapped inside the cells was greater in cultures treated with chlorfenvinphos, wherea s quenching of ACMA fluorescence was found to be greater with dimethoa te treatment. A marked difference between the effects of dimethoate an d chlorfenvinphos on permeability changes in the plasma membrane of Sy nechocystis was also noted. The release of cellular organic carbon was observed at each concentration of chlorfenvinphos, whereas with dimet hoate such an effect was noted at greater than or equal to 200 mu mol liter(-1). The rate of uptake of substrates like 2-deoxyglucose and 2- aminoisobutyric acid (AIBA) was significantly (negatively) correlated with concentrations of both the insecticides. Chlorfenvinphos was more effective than dimethoate in reducing the active uptake of nonmetabol izable sugar and amino acid analogues, (C) 1998 Academic Press.