Orthovanadate at concentrations of 20 to 500 $\mu M$ markedly inhibits growth (as increase in fresh weight), net $K^{+}$ uptake and acidification of the medium for the incubation of germinating radish seeds. These data can be related to the previous finding that in membrane preparations from germinating radish seeds orthovanadate inhibits a non mitocondrial, $K^{+}$, $M^{++}$-stimulated ATPase activity, tentatively identified with a plasmalemma ATPase involved in electrogenic proton extrusion.