Measurements of sap flow density (SFd) in different organs of oak tree (Quercus pubescens) infested by Loranthus europaeus were performed at the Pouzdrany steppe (Czech Republic). Sap flow was measured in a deep root, two shallow roots, two sides of stem, four oak branches, three oak branches infested by mistletoe and two male mistletoe plants using single- and three-point heat field deformation (HFD) sensors. Evaluated period consisted of three days with high reference evapotranspiration (PET) followed by one day with rain events and two following days without rain. The Loranthus europaeus participated to transpiration process with large amount of water from its storage tissues. This hemiparasitic plant more drove afternoon and night flows in host tree independently to drought stress. Deep roots substantially participate to daily water flow in tree especially during drought. Reverse flow in shallow roots was observed under soil drought conditions and low PET as deep root supplied water in process of hydraulic lift. Situation changed after the rains, when reverse flow in the deep root was observed during two nights indicating hydraulic descent. Availability of soil water after the rain caused replenishing of host and hemiparasite storage tissues, increased transpiration of oak branches, increased hysteresis of SFd in mistletoe branches (prolonged lag by depletion and refilling of succulent-like leaves) and enhanced participation of shallow roots to transpiration and tissue refilling.