Electrolytic Conductivity — a Rapid Measure of Herbicide Injury

Abstract

The use of electrolytic conductivity as a measure of cell membrane disruption was tested on buckwheat (Fagopyrum esculentumMoench. cv. ‘Tokyo’) plants which had been sprayed with paraquat (1,1′-dimethyl-4,4′-bipyridinium ion) or oxyfluorfen [2-chloro-1-(3-ethoxy-4-nitrophenoxy)-4-(trifluoromethyl)benzene]. All treatments which resulted in tissue damage caused significant increases to the solutions where the discs were floated for measurement. The highest conductivity measurement (most membrane disruption) was obtained from paraquat. The highest concentration for each herbicide gave higher conductivity measurements than lower concentrations. A difference in the pattern of conductivity change induced by the two chemicals implies a different mode of action for each.

A rapid sensitive bioassay for determination of paraquat and diquat in water

“…With the Cotyledon disc bioassay a 15 h incubation period was required to detect 10-*M paraquat (Da Silva et al, 1976). It is difficult to compare the present data where plants were floated on solutions of diquat and paraquat with those of the conductivity method used by Vanstone & Stobbe (1977), where paraquat was sprayed on to leaves of buckwheat. It is evident, however, in the latter method that visible injury was required before changes in conductivity were detected, whereas, in this work increased membrane permeability was observed more rapidly and without appearance of injury symptoms.…”

“…With diquat the concentrations were 0-018 /jg/ml after 12 h, 0-0018 /ig/ml after 24 and 48 h, and 0-00018 /ig/ml after 72 h. At these minimum concentrations no visible injury, such as, chlorosis, was evident. Other studies showed that increase in leaf-cell membrane permeability (Prendeville & Warren, 1977;Vanstone & Stobbe, 1977) in Phaseotus vulgaris L. and Fagopyrum esculenlum Moench (buckwheat) induced by paraquat was always associated with injury symptoms such as necrotic areas in leaves. Treating the plants with diquat and paraquat for longer than 72 h did not signiflcantly increase the sensitivity ofthe bioassay.…”

“…To date these include a cotyledon disc bioassay (Da Silva, Fadayomi & Warren, 1976), an electrolytic conductivity method (Vanstone & Stobbe, 1977) a bioassay for the determination of low concentrations of paraquat (Damanakis, 1970) and appearance of chlorosis in Lemna minor was used to detect diquat and paraquat in solution (Funderburk & Lawrence, 1963), In the present study we describe a rapid sensitive bioassay whereby changes in membrane permeability in Lemna minor were correlated with paraquat and diquat levels in solution.…”

Toxic effects of surfactants applied to plant roots

“…After 1 h, the conductivity of the following surfactant solutions was significantly (at 1 % probability) higher than in the control: II and IV at both concentrations and V at the higher concentration (11)…”

Basis for changes in glyphosate phytotoxicity to barley by the non‐ionic surfactants Tween 20 and Renex 36*

“…Leakage of electrolytes, as measured by changes in solution conductivity, was used as an indicator of alteration of membrane integrity. This technique has also been used by other workers as an indicator for herbicide injury (Vanstone & Stobbe, 1977;O'Brien & Prendeville, 1978;O'Donovan, O'Sullivan & Caldwell, 1983).…”