A Survivor

This is a prickly pear cactus (opuntia) growing high in the White Mountains of Arizona above 8000 feet. We often associate cactus with the desert and hot temperatures, but prickly pears grow north into areas where the Winter temperatures drop to 20 degrees below zero or lower. How does a plant that is mostly water survive the low temperatures every year, year after year? If you want the technical reasons you can read, Water Relations and Low-Temperature Acclimation for Cactus Species Varying in Freezing Tolerance from Guillermo Goldstein and Park S. Nobel of the Department of Biology and Laboratory of Biomedical and Environmental Sciences, University of California, Los Angeles, California. This is one of those topics that seem to be difficult for scientists to handle. You have a problem that seems obviously impossible, a plant that is mostly water that doesn't die when it is subjected to extreme freezing temperatures. So, the scientists dismiss the problem for years until someone points out the obvious, that this cactus is growing in an area where the temperatures are well below freezing. How old is this cactus? How long to do they live? All of these questions seem like they are begging for answers. Don't you think that if you want to better understand what you think is normal, you start with what seems impossible?