Uncoupling proteins play a role in normal physiology, as in cold exposure or hibernation, because the energy is used to generate heat (see thermogenesis) instead of producing ATP. Some plants species use the heat generated by uncoupling proteins for special purposes. Skunk cabbage, for example, keeps the temperature of its spikes as much as 20° higher than the environment, spreading odor and attracting insects that fertilize the flowers.[4] However, other substances, such as 2,4-dinitrophenol and carbonyl cyanide m-chlorophenyl hydrazone, also serve the same uncoupling function.