The effect s of rootstock vigour on scion xylem hydraulic conductivity were studied on potted trees of cv. 'Armking' nectarine grafted on GF677 (vigorous) and MrS 2/5 (low-vigour) rootstocks. Water potential gradients of non-transpiring leaves, were measured at three levels of the stem starting at 10 cm above the graft-point. Transpiration rate was estimated by weighing. On the same trees, two sets of measurements were taken, at two different transpiration-rate levels obtained imposing a different level of evaporative demand. Measurements were taken after allowing transpiration to reach steady-state (20 minutes after any environmental perturbation). Trees grafted on the low-vigour rootstock (MrS 2/5) showed the lowest water potential at any level along the stem and the lowest hydraulic conductivity along the stem, about half the values observed on GF677-grafted and self-rooted trees.