Investigations into the Occurrence of Active and Passive Components in the Ion Uptake by Vicia faba

The relation between water uptake and ion uptake has been investigated at various experimental conditions using 5-7 weeks old Vicia faba plants. Taking the uptake from a calcium chloride solution as a control, the relation between ion uptake and water uptake could be modified by using sugars and inhibitors. Applying sugars to the nutrient solution the concentration of the transpiration stream could be enhanced. Using inhibitors this concentration decreased. The concentration of the transpiration stream amounted to about 13 % of the concentration in the outer solution on aerated calcium chloride solution, to about 24 % on calcium chloride solutions with sugar addition and to about 2—4 % using dinitrophenol addition or a non-aerated solution. It is assumed that these facts indicate that a dominant part of the ions in the transpiration stream arrives there by means of a process dependent on metabolism. Only a small percentage of the total ion transport seems to be due to a passive carrying along with the transpiration stream.