The ATP-inhibited Plant Mitochondrial $K^+$ Channel ($PmitoK_{ATP}$) was discovered about fifteen years ago in Durum Wheat Mitochondria (DWM). $PmitoK_{ATP}$ catalyses the electrophoretic $K^+$ uniport through the inner mitochondrial membrane; moreover, the co-operation between $PmitoK_{ATP}$ and $K^+/H^+$ antiporter allows such a great operation of a $K^+$ cycle to collapse mitochondrial membrane potential (${Delta}{Psi}$) and ${Delta}pH$, thus impairing protonmotive force (${Delta}p$). A possible physiological role of such ${Delta}{Psi}$ control is the restriction of harmful reactive oxygen species (ROS) production under environmental/oxidative stress conditions. Interestingly, DWM lacking ${Delta}p$ were found to be nevertheless fully coupled and able to regularly accomplish ATP synthesis; this unexpected behaviour makes necessary to recast in some way the classical chemiosmotic model. In the whole, $PmitoK_{ATP}$ may oppose to large scale ROS production by lowering ${Delta}{Psi}$ under environmental/oxidative stress, but, when stress is moderate, this occurs without impairing ATP synthesis in a crucial moment for cell and mitochondrial bioenergetics.