The Effects of Vitamin K3 and Dicumarol on the Plasma Membrane Redox System and H+ Pumping Activity of Zea mays L Roots Measured over a Long Time Scale

The effects of vitamin K3 or dicumarol on plasma membrane bound hexacyanoferrate (III) and hexabromoiridate (IV) reductase activity and on the H+ pumping rate were investigated. Incubation with vitamin K3 followed by intense rinsing stimulated the subsequent reduction of hexabromoiridate (IV) and hexacyanoferrate (III) as well as proton secretion induced by external electron-acceptors, while pretreatment with dicumarol inhibited proton secretion induced by redox activity and hexacyanoferrate (III) reduction rate, but not the effects of hexabromoiridate (IV). A 30 min incubation in 0·2 mM K3 or dicumarol, followed by rinsing, inhibited H+ secretion for about 2 d. Incubation for more than 12 h in 0·1 mM dicumarol or 0·2 mM K3 caused lethal injury to the root cells.