Polyethylene glycol (PEG)-induced water stress in nutrient solutions decreased both water consumption and 45Ca uptake by apple seedlings (Malus domestica Borkh.) The decrease in water uptake was more severe than the decrease in 45Ca uptake. When 45Ca uptake was calculated on the basis of water consumption, it was found that 45Ca uptake was not dependent on water uptake although water was necessary for movement of 45Ca. In split-root experiments, PEG and 45Ca were either applied to the same half of the root or to separate halves. Calcium uptake decreased in plants subjected to water stress. The results indicated that the site of this decrease was at the root, not the aerial portion of the plant which, indirectly, may affect root function and thus 45Ca uptake. Split-root experiments also indicated that the unstressed half of the root cannot fully compensate for the stressed half of the root in either water or 45Ca uptake. Water use of plants with half of their root under a −5.0 bar water stress was decreased by 30%. Urea-nitrogen pretreatment did not modify the effect of osmotic stress on leaf Ca, Mg and K concentrations, water use or dry matter production during the period of applied water stress. All these parameters decreased with increasing solution osmotic stress.