Long chain bases or sphingoid bases are building blocks of complex sphingolipids that display a signaling role in programmed cell death in plants. So far, the type of programmed cell death in which these signaling lipids have been demonstrated to participate is the cell death that occurs in plant immunity, known as the hypersensitive response. The few links that have been described in this pathway are: MPK6 activation, increased calcium concentrations, and reactive oxygen species (ROS) generation. The latter constitute one of the more elusive loops because of the chemical nature of ROS the multiple possible cell sites where they can be formed and the ways in which they influence cell structure and function.