Esterase inhibition by organo-phosphorus residues, with some observations on possible effects on plant metabolism

Organo-phosphorus residues in tissues of sprayed plants were detected by estimating the esterase-inhibiting activity of their leaf and root extracts. This method was used to examine the anti-esterase effects of mangold plants that had been sprayed with Systox, parathion and Hanane. Extracts of leaves of these treated plants were shown to inhibit added choline esterase for some weeks after treatment. The enzymic hydrolysis of phenyl acetate by extracts of leaves and roots of mangold plants treated with these insecticides was reduced for varying periods of up to 8 weeks. Assays of parts of bean plants that had been sprayed with demeton-S showed that anti-esterase activity was limited to those parts that had been sprayed : tissues developed subsequent to spraying showed no such effects. Leaves sprayed about 2 months previously inhibited added choline esterase and showed reduced activity in hydrolysing phenyl acetate. There is some evidence that substances, possibly substrates in the plant enzyme systems affected, accumulate in treated leaves.