Water Uptake from Water and Salt Solutions

The aim of the investigation was an analysis of the transference reactions (tiberfiihrungsreaktionen). These reactions were studied with bean plants. At transference of the root system of an intact transpiring plant from distilled water to a salt solution the water uptake decreases instantaneously. Thereafter a gradual increase is found until a new constant level is reached. At transference from a salt solution to distilled water the water uptake increases and shows a gradual decrease to a constant level. It is shown that this course of the water uptake by far the greatest part is regulated by the mechanical suction tension in the xylem vessels and that only a small fraction of the water uptake is due to osmotic forces. The experimental set-up rendered it possible to make a separation of these two mechanisms. It appeared to be possible to inhibit the nearly fully mechanic water uptake by means of an osmotic counter suction in the medium.