HEAT-PRODUCTION OF ROOT-CELLS UPON THE DISSIPATION OF ION GRADIENTS ON PLASMA-MEMBRANE

The dissipation of ion gradients across plasma membranes contributes t o the heat production by live cells. The aim of the present research i s to determine the dependence of the rate of hear production by plant tissues on ion balance shifts, supposing a priori that the shifts are the beginning mechanism in adaptation to various stresses. Excised whe at roots subjected to prolonged incubation in different solutions serv ed as objects for investigation. Two ion transporters (K+/H+-transport er nigericin and Ca2+-ionophore A23187) shifted the ion homeostasis an d induced distinct changes in the energy metabolism of plant tissues. Nigericin, which considerably increased the plasmalemma conductivity f or protons and potassium, enhanced production of heat by root cells th roughout the exposure. Prolonged incubation with A23187 was required t o display its ion-transporting properties which were accompanied by a rise in the rate of heat release. The high rate of heat release and re spiration in root cells exposed to ion transporters is a reflection of the ion-gradient dissipation and the increased energy expenditure for the activation of ATPase systems necessary for the restoration of ion ophore-disturbed ion homeostasis. (C) 1998 Elsevier Science B.V.