The Water Relations of Pinus sylvestris

Comparative field studies of transpiration rate and drying-transpiration in Scots pine were carried out in the autumns of 1964 and 1965 and in the early summer of 1966. The experimentl material was nineteen to twinty year old grafts, of the same clone but growing on different types of ground, or of different clones but growing in close proximity and under the same environmental conditions. Transpiration rates were measured on detached shoots. The results indicated that the type of ground did not very much modify the responses of the shoots to illumination-darkness treatment. Drying-transpiration is here defined as the transpiration occurring when detached shoots are prevented from water uptake. Measurements were made of the rate of loss of weight and the amount of water given off from illuminated shoots. Defferences were found both in the rate of weight loss, and in the amount of water given off, between pine trees of the same clone but growing on different types of ground, and between pine trees of different clones but growing on the same type of ground.