T. 1990. Boron is required for the stimulation of the ferricyanide-induced proton release by auxins in suspension-cultured cells of Daueus carota and Lycopersicon esculentum. -Physiol. Plant. 80: 114-118.Boron deficiency reduces the ferricyanide-induced net proton release of suspensioncultured carrot {Daueus carota L.) and tomato {Lycopersicon esculentum Mill.) cells by more than 50%. This effect is reversed within 60 to 90 min by the addition of B. Vanadate (400 |iAf) completely suppresses the proton release, indicating an ATPasedriveu process. The differences between B treatments do not appear when auxins are omitted from the experimental solution, but can be observed within less than 30 mio after the addition of auxin to auxin-deficient cell cultures. This suggests, that an adequate supply of B is required for the auxin action to take place. The results are discussed with respect to the primary functions of B in membranes and transport processes, and its possible influence on auxin-ioduced metabolic events.