Effects of ecotoxicological chemicals on passive plasmalemma permeability in plants

The measurement of changes of electrical conductivity in the external medium of isolated mesophyll protoplasts of Vicia faba, tissue disks of red beetroot (Beta vulgaris), and intact duckweed plants (Lemna gibba) was used to determine nonspecific electrolyte efflux. This provided rapid screening tests to assess the impact of environmental chemicals on passive membrane permeabilities. The conditions of the tests and their applicability to environmental studies are described in detail. Twenty-five reference chemicals selected by the Bundesminister für Forschung und Technologie (BMFT, FRG) were tested. The sequence of effectiveness of the various substances was similar in the different test systems and appeared to be independent of the organizational level of the plant material. Passive electrolyte efflux was most effectively stimulated by HgCl2, pentachlorophenol (PCP), and sodium dodecylbenzenesulfonate (LAS). The threshold concentrations showing clear stimulation of electrolyte efflux after 3 hr of application with protoplasts and 24 hr with tissue disks were in the vicinity of relevant environmental levels. The tests described allow the detection of effects at least down to concentrations of 0.004 mol m-3 HgCl2, 0.001 mol m-3 PCP, and 0.04 mol m-3 LAS. Other putatively very toxic chemicals were ineffective in these short-term permeability tests.