Electrical Coupling, Potentials, and Resistances in Oat Coleoptiles: Effects of Azide and Cyanide

Electrophysiological measurements were made on oat coleoptile(Avena sativa L. cv. Victory) parenchyma cells. Both 1 mM potassiumcyanide and 1 mM sodium azide cause reductions in cell restingpotential and electrical coupling and an increase in the combinedtonoplast and plasmalemma resistance. The reduction in coupling is probably attributable to a decreasein current flow through plasmodesmata, resulting from an increasein plasmodesmatal resistance. Potassium cyanide also induces some callose formation withincell walls and this may contribute to the observed reductionin coupling. However, sodium azide does not induce callose formation.Presumably other processes are involved in the reduction ofcoupling which are not attributable to callose.