XVI International Botanical Congess

The effect of aluminium - induced changes in membrane potential and the activity of potassium ions was studied in the root hairs of Trianea bogotensis Karst., grown in Hoagland-Arnon 1 nutrient medium at varions pH level. An increase in Al concentration in an acid medium had a depressive effect on bioelectric activity and decreased potassium accumulation in root epidermal cells. At the same time, the removal of the meristematic root tip did not change the value of membrane potentials but degree of its variation increased. The distribution of potassium ions in root epidermal cells and the direction of its electrochemical gradients between epidermal cells and between the cells and the medium were in direct relation with growth zone and root hairs functional state. The obtained data indicate to the importance of root tip for regulation potassium transport in root cells under these conditions. It was supposed that Al effect in medium at low pH is realised by the regulation of cytokinins synthesis in root apex. The role of root tip and the mechanism of its effect on H+ pumps at the plasmalemma under Al stress action are discussed.