Changes in the Energy State of Wheat Root Cells Induced by the Protonophore CCCP

The effects of carbonyl cyanide 3-chlorophenylhydrazone (CCCP) on the rate of the oxygen uptake by excised wheat roots and their heat generation and K+ion content in the incubation medium were followed for 6 h. When the incubation medium contained 0.5 μM CCCP, the roots were found to exhibit a reversible release of K+ions and the stimulation of the oxygen uptake. These responses were found to correlate with considerably enhanced heat generation by the plant tissues. It is proposed that these changes were due to the activation of both the energy system of the root cells and the H+-ATPase in the plasmalemma. The roots treated with 5 μM CCCP exhibited an inhibition of the oxygen uptake and heat generation (1–3 h) followed by the stimulation of these processes by the 5th or 6th hour of the experiment; however, the potassium ion release by the roots was not reversed under these conditions. Uncoupling the processes of oxidation and phosphorylation in mitochondria of the root cells (the 4th–6th h) seems to underlie the observed responses. In the roots treated with 50 μM CCCP, we observed the irreversible release of K+ions from the root cells, the considerable inhibition of the oxygen uptake by the latter, and the initial burst and then decline in heat generation. These effects suggest that, under the experimental conditions, a disturbance in cellular homeostasis and energy supply occurred and eventually resulted in cell death.