Using 86Rb as an analogue for K+, the uptake of K-ions in 15 mg during one hour in labelled KCl (1 mmolar) solution has been found to be very significantly different in tissue from living twigs of woody plants compared with that from dead twigs. This uptake test has been successfully applied to twigs and discriminates among living, damaged and killed tissue. A modification can assess damage to buds. Ion uptake results supplement the results of electrical cambial capacitance, measured at temperatures 10–25 °C.Key words: Tissue, viability, ion uptake