Saponin(s) was extracted from tea seeds, and its effect on the vase life, transpiration from leaves and hydraulic conductance of stem segments in cut roses (Rosa hybrida L. cv. Sonia) were investigated. The continuous treatment with tea-seed saponins (TSS) at 20 mg L^-1 significantly extended the vase life of cut rose flowers, but those at other concentrations did not. The volume of water uptake and water loss by the cut flowers decreased with increasing concentration of TSS. TSS induced stomatal closure. In cut flowers kept in water, hydraulic conductance of the stem segment decreased with time,and 20 mg L^-1 TSS treatment considerably suppressed this decrease. The results show that TSS markedly inhibited transpiration from leaves and suppressed decrease in hydraulic conductance, which may be responsible for a significant increase in vase life.