RESUMO
Effect of fenitrothion (phosphorothioic acid, 0,0-dimethyl 0–4-nitro-m-tolyl ester), an organophosphorous insecticide, on membrane permeability employing the leakage of betacyanin and electrolytes as the criteria were studied in beet root (Beta vulgaris) discs. The leakage of both betacyanin and electrolytes increased with increasing concentrations (10-150 ppm) of fenitrothion in the incubation medium. At 0.33 mM the increase in electrolyte leakage was approximately linear for the first 6 h, while the increase in betacyanin leakage started with a lag of about 2 h. Long term incubation (24 h) showed a biphasic nature (in the semilog plot) for the increase in betacyanin leakage, while the increase in electrolyte leakage appeared more complex. In the control sample, the Arrhenius plots (25-50°C) of leakage showed a break at 40°C. In treated samples no breax was observed, but the slope decreased (for both electrolyte and betacyanin leakage) as compared to the respective slopes in the control in the temperature region greater than 40°C. The results are discussed in terms of the possible effect of the insecticide on the active transport in plant membranes