MODIFICATION OF THE ACTIVITY OF THE PLASMA-MEMBRANE REDOX SYSTEM OF ZEA-MAYS L ROOTS BY VITAMIN-K3 AND DICUMAROL

The correlation of the effects of vitamin K3 and dicumarol (an anti-vitamin K in pharmaceutical applications) on the transplasma membrane electrical potential difference of maize roots with the reduction of the artificial electron acceptors hexacyanoferrate (III) or hexabromoiridate (IV) and the concomitant enhancement of acidification of the incubation medium was investigated. Vitamin K3 depolarized the plasma membrane of Zea mays L. roots, while dicumarol had no significant effect on the membrane potential. Plants treated with vitamin K3 for 30 min followed by intense rinsing showed higher reduction of hexabromoiridate (IV) than hexacyanoferrate (III), as well as a stimulated acidification of the incubation medium. Depolarization of the plasma membrane by hexacyanoferrate (III) or hexabromoiridate (IV) decreased after an incubation with vitamin K3. Pretreatment with dicumarol caused an inhibition of hexacyanoferrate (III) reduction and medium acidification as well as depolarization by K3. The reduction of hexabromoiridate (IV) was not affected by dicumarol pretreatment. The proton secretion associated with the reduction was slightly lowered. According to our results, it seems possible that vitamin K3 acts as an electron acceptor for the plasmalemma electron transport system of maize roots whereas dicumarol appears to inhibit electron and proton transport.