Electron transport in plant mitochondria generally displays some degree of resistance to cyanide, the inhibitor of cytochrome oxidase. The extent of cyanide resistance can fluctuate between a few percent and nearly 100% and is markedly dependent on the nature of the substrate being oxidized (l-3). These observations have led to the proposal that plant mitochondria possess two pathways to carry electrons to oxygen: the well-known cyanide-sensitive cytochrome pathway and the cyanide-resistant, nonphosphorylating alternative pathway. Both pathways share ubiquinone as a common electron carrier (4). These facts are now well established and are summarized in recent review articles (5-7).