Global warming as the nowadays issue leads to investigate on the phenomenon of tree cavitation to take a better account of drought tolerance mecanisms in plants. A lack of knowledge on residual transpiration role in cavitation risks after stomatal closure is to deplore unlike all the studies carried on stomatal transpiration, major factor responsible of embolism onset in xylem vessels. The aims of this study is to determine if the measure of residual transpiration is gravimetrically feasible and to what extend it has an impact on plant vulnerability to drought stress. To that end, well watered and hydric stressed Populus tremula x alba half-defoliated and whole plants and leaves have been put on scales and their loss of weight have been registered over time. Emboli rate course have been measured over time too for whole and half-defoliated water stressed plants. Findings indicate that gravimetric method allows to see in vivo residual transpiration over time but also that it is not successful enough to show differences between non and half-defoliated conditions. In contrast, emboli rate measurements prove residual transpiration role in cavitation emergence.