Molecular oxygen is the terminal electron acceptor in the mitochondrial electron transport chain and is required by several enzymes, higher plants need oxygen for growth and metabolism. But frequently they experience oxygen deficiency in the root-zone mainly due to soil waterlogging、soil compaction and submergence. Apple is one of the most important fruit crops in the world; hypoxia stress in the root-zone is thought to be one of those important factors which restrict the development of apple. 12 app...