The mechanism and biological role of calcium transport by plant mitochondria.

Using a tetraphenylphosphonium-sensitive electrode, a linear relationship was obtained between membrane depolarization during Ca2+ influx into plant mitochondria and the rate of respiration when the rate of succinate oxidation was gradually inhibited by increasing concentrations of malonate. These results are consistent with the existence of electrogenically-mediated Ca2+ transport in the mitochondrial membrane, driven by the protonmotive force. The data are discussed in terms of the biological role of such a Ca2+ transport system in plant mitochondria.