Responses of the root systems of two conifer species (Pinussylvestris L. and Piceaabies (L.) Karst.) in a strongly acidic mineral soil and in a soil with normal acidity to increasing water deficits and subsequent rewatering were examined in a growth chamber experiment. Two-year-old greenhouse seedlings were transplanted into transparent acrylic containers (rhizotrons) positioned at an angle of 45° in wooden boxes. During the 12-week test duration, the following root parameters were measured in intervals of 2 to 4 days: root elongation rate, number of growing roots, root diameter, development of root hairs, root browning, and the development of mycorrhizae. The test plants, the spruces more so than the pines, in the strongly acidic soil were limited in their ability to react to changes of the water supply. Of the examined root parameters, the root elongation rate and the number of growing roots showed the most distinct reactions.